Journal of Porphyrins and Phthalocyanines

The aim of this review is to offer an update on the preparation and functionalization of porphycenes and expanded porphycenes covering the period of 2017 to 2022.

Metalloporphyrins, metallophthalocyanines, and analogs are known to act as efficient catalysts for the reduction of dioxygen in the presence of an acid in solution. Whether dioxygen is reduced to hydrogen peroxide (H₂O₂: two-electron reduced species of O₂) or water (H₂O: four-electron reduced species of O₂) is changed depending on metals and ligands. This mini-review focuses on the catalytic production of hydrogen peroxide by a combination of 2e⁻O₂ reduction and 2e⁻or 4e⁻ H₂O oxidation with the use of metalloporphyrins and metallophthalocyanines as photocatalysts. H₂O₂generated by the photocatalytic H₂O oxidation with O₂ can be used as a fuel in hydrogen peroxide fuel cells in which metalloporphyrins, metallophthalocyanines, and analogs are employed as the cathode catalysts. Metalloporphyrins are also employed as efficient electrocatalysts to exhibit significantly improved performance in a Zn-air battery that has a much higher energy density than that of lithium-ion batteries.

Electro and photochemical ${\mathrm{\text{CO}}}_2$ reduction (${\mathrm{\text{CO}}}_2$R) has emerged as a contemporary research field for tackling the fossil fuel problems and construction of a modern chemical industry. For efficient ${\mathrm{\text{CO}}}_2$R, a catalyst is needed, and Earth-abundant Fe, Co, and Ni-based metalloporphyrinoids have appeared as promising molecular catalysts for ${\mathrm{\text{CO}}}_2$R. Several metal complexes of porphyrins, phthalocyanines, corroles, and chlorins-type porphyrinoids have been designed and tested for this purpose. The unique advantages in the judicious tuning of the porphyrinoid structures and their susceptibility towards different functionalization reactions allow an impressive scope to explore and establish a direct structure-activity relationship of metalloporphyrinoids towards ${\mathrm{\text{CO}}}_2$R. There have been rapid advances in this field in the last few years. For the homogeneous ${\mathrm{\text{CO}}}_2$R, the electronic and steric aspects of the porphyrinoids are fine-controlled by installing favorable functional groups at the periphery of the porphyrinoids. On the other hand, in heterogenous ${\mathrm{\text{CO}}}_2$R, the design principle is guided by integrating metalloporphyrinoids in composite material after mixing with carbon supports, semiconductors, or adopting reticular chemistry. All the advancements further result in the testing of excellent metalloporphyrinoids in industrially feasible ${\mathrm{\text{CO}}}_2$ electrolyzers or photoelectrochemical devices. This review focuses on the recent advances in designing principles of metalloporphyrnoids catalysts in homogeneous, heterogeneous, and ${\mathrm{\text{CO}}}_2$R reactors.

Our groups are involved in a research program on the development of molecular and supramolecular systems combining pillar[5]arene building blocks with porphyrins. Functionalization of both rims of the pillar[5]arene scaffold with metalloporphyrins generated giant molecular machines mimicking the blooming of a flower as well as light-harvesting devices. On the other hand, we have also used the host-guest properties of pillar[5]arene derivatives to prepare photoactive mechanically interlocked molecules. In such compounds, complementary subunits are associated into a single molecular ensemble but without being connected through covalent bonds. Inter-component photo-induced energy transfer processes remain however extremely fast in these systems despite the exclusive link through mechanical bonds. All these results are described in the present review.

Hemihexaphyrazines can be considered as hexamembered porphyrinoids of the ABABAB type, where thiadiazole rings (A) and pyrrole-containing subunits (B) joined via aza bridges to form a macrocyclic system with an expanded coordination cavity capable of holding at once three atoms of transition metals that are formed a triangular cluster. It was established for the first time that unsubstituted hemihexaphyrazine and its metal complexes can be reduced to form crystalline salts. These salts were characterized by UV-Vis-NIR and IR spectroscopy, MS, and X-Ray diffraction data. The magnetic properties of these compounds were studied for the first time using EPR and SQUID techniques within the $1.9–300$ K temperature range. It was shown that the three-electron reduction of starting ${\{{{\mathrm{\text{M}}}^{\mathrm{\text{II}}}}_3\mathrm{\text{O}}(\mathrm{\text{Hhp}})\}}^{+}$ yields ${\{\mathrm{\text{cryptand}}({\mathrm{\text{Cs}}}^{+})\}}_2{\{{{\mathrm{\text{Ni}}}^{\mathrm{\text{II}}}}_2{\mathrm{\text{Ni}}}^{\mathrm{\text{I}}}\mathrm{\text{O}}({\mathrm{\text{Hhp}}}^{5-})\}}^{2-}\cdot 2{\mathrm{\text{C}}}_7{\mathrm{\text{H}}}_8$ and ${\{\mathrm{\text{cryptand}}({\mathrm{\text{Cs}}}^{+})\}}_2{\{{{\mathrm{\text{Cu}}}^{\mathrm{\text{II}}}}_3-\mathrm{\text{O}}({\mathrm{\text{Hhp}}}^{•6-})\}}^{2-}\cdot {\mathrm{\text{C}}}_7{\mathrm{\text{H}}}_8$ crystalline salts. An unusual doublet-quartet transition was found for the ${\{{{\mathrm{\text{Ni}}}^{\mathrm{\text{II}}}}_2{\mathrm{\text{Ni}}}^{\mathrm{\text{I}}}{\mathrm{\text{O}}}^{-}({\mathrm{\text{Hhp}}}^{5-})\}}^{2-}$ dianions. Salt ${\{\mathrm{\text{cryptand}}({\mathrm{\text{Cs}}}^{+})\}}_2{\{{{\mathrm{\text{Ni}}}^{\mathrm{\text{II}}}}_2{\mathrm{\text{Ni}}}^{\mathrm{\text{I}}}\mathrm{\text{O}}({\mathrm{\text{Hhp}}}^{5-})\}}^{2-}\cdot 2{\mathrm{\text{C}}}_7{\mathrm{\text{H}}}_8$ also shows an unusually strong low energy NIR absorption, which was observed at 1000–2200 nm with maxima located at 1283 and 1980 nm. A phenomenon consisting of equalization of bond lengths among exocyclic nitrogen atoms (${\mathrm{\text{N}}}_{\mathrm{\text{ex}}})$ and neighboring atoms C(pyrrole) and C(thiadiazole) was observed under reduction conditions.

Meso-free B(III)subchlorin has been synthesized for the first time using meso-trifluoromethyl substituted tripyrrane, in trace quantity. It displays the most-blue shifted absorption and emission for subchlorins. This macrocycle was found to be completely resistant to oxidation and moderately generate singlet oxygen (34 %).

Dipyrrolylbenzenes bearing a tethered carboxylate unit with a countercation have been synthesized as components of anion-binding self-assemblies via hydrogen bonding between the anionic moieties and pyrrole NH units. The 1D-chain self-assembled structures, as negatively charged supramolecular polymers, provide solid-state ion-pairing assemblies, whose assembly modes depend on the coexisting cations.

A new convergent synthetic methodology has been adopted for syntheses of two hitherto unknown new generation of core-modified N-confused calixphyrins and an all four meso-sp³ centered heterocyclic macrocycle with $\beta$,$\beta$-pyrrole connectivities via acid catalyzed Lindsey type condensation of thiophene diol with N-protected pyrrole(s) using BF₃.Et₂O followed by oxidation with chloranil. All of the macrocycles have been achieved in moderately good yields. Their structures, electronic and optical properties have been elucidated by NMR, UV-Vis-NIR spectroscopic analyses and in-depth theoretical calculations. The type of macrocycles are a mere consequence of the type of N-protected pyrroles used as synthons with the UV-Vis spectra closely resembling the spectra for calixphyrins. Detailed structural analyses using ¹H-¹H (COSY, ROESY), ¹³C-¹H (HSQC) 2D NMR studies and DFT level theoretical investigations indicated lack of macrocyclic $\pi$ conjugation with $\alpha$,$\beta$ and/or $\beta$,$\beta$ pyrrole connectivities.

Rhodium(I) complexation of meso-free $\beta$-dibromo-N-fused [22]pentaphyrin 3 afforded mononuclear Rh(I) complex 5, whose structure was confirmed by X-ray crystallographic analysis. Hydrodebromination of 3 gave meso-free N-fused [22]pentaphyrin 4as the first example of $\beta$-unsubstituted meso-free N-fused pentaphyrin. Chlorination of 4 with Palau’chlor afforded the corresponding mono- and dichloropentaphyrins 9 and 10. Their structural identification and electronic properties were reported.

As naturally occurring bacteriochlorophyll-$d$ models, zinc methyl (3¹R)-bacteriopheophorbides-$d$ possessing ethyl, vinyl, and ethynyl groups at the 3²-position were prepared by chemically modifying chlorophyll-$a$. The synthetic molecules self-aggregated in an aqueous Triton X-100 micelle solution similarly as in the major light-harvesting antenna of photosynthetic green bacteria to give supramolecularly ordered large oligomers with red-shifted and broadened visible absorption bands, compared with the monomeric bands. The sequential hydrogenation of the 3²-ethynyl to ethyl group via the vinyl group gradually suppressed the chlorosomal self-aggregation ability. The successive elongation of the 3¹-alkyl chain from a methyl to propyl group via an ethyl group also diminished the $J$-aggregation ability. These decreases in the self-aggregation were ascribable to the steric enhancement of the 3²-substituents near the 3¹-hydroxy group requisite for the $J$-aggregation.

2,2$\prime$-Biphenyl-fused Ni(II) porphyrins were synthesized by two methods. One was oxidative fusion reaction of meso-(biphen-2-yl)-substituted Ni(II) porphyrin with the combination of 2,3-dichloro-5,6-dicyano-$p$-benzoquinone (DDQ) and Sc(OTf)₃ and the other was Pd-catalyzed intramolecular cyclization of meso-(2$\prime$-chlorobiphen-2-yl)-substituted Ni(II) porphyrin. These fused products showed contorted structures owing to the installed seven-membered carbocycle(s) that were revealed by X-ray crystallographic analysis and exhibited moderately red-shifted absorption bands.

Designing stable molecules with near-infrared (NIR) absorption and good light-to-heat conversion performance is important for phototherapy applications. Herein, we report the synthesis of copper-coordinated meso-tetrakis(triisopropylsilylethynyl)-tetranaphthoporphyrin 2-Cu by retro-Diels Alder reaction, which exhibited a Soret band at 534 nm and a NIR Q band at 818 nm. The single-crystal X-ray analysis of 2-Cu revealed a purely ruffle-distorted conformation with an S4 symmetry axis. Theoretical calculations show that 2-Cu has a narrower HOMO-LUMO gap than its meso-phenyl and meso-free analogs due to a decrease in LUMO energy level. The photothermal investigation of 2-Cu under 808 nm laser irradiation demonstrated its outstanding photostability and high photothermal conversion efficiency, indicating its promise as a photothermal therapeutic agent after functionalization.

Recently, norcorrole Ni(II) complexes have received much attention because they exhibit peculiar solid-state structures and fascinating electronic properties originating from their distinct antiaromatic character. In this work, we have prepared a norcorrole Ni(II) complex with 5-hexylthien-2-yl substituents at the meso-positions, of which the antiaromatic nature was evaluated by ¹H NMR analysis as well as NICS and ACID calculations. The X-ray diffraction analysis elucidated its molecular structure and crystal packing arrangement. Crystal packing structures of Ni(II) meso-di(5-methylthien-2-yl)norcorrole and Ni(II) meso-di(5-hexylthien-2-yl)norcorrole were markedly different. The latter provided a polar crystal because of the unidirectional alignment of 5-hexylthien-2-yl groups in the solid state.

Recently, porphyrin derivatives having ring-fused structures at the periphery have attracted attention by virtue of their unique optoelectronic characteristics. This manuscript surveys the syntheses and properties of porphyrin derivatives having fused five-membered rings at the periphery. Porphyrin derivatives with fused five-membered rings have been revealed to exhibit unique properties, which are different from those having fused six-membered rings at the periphery. For instance, porphyrins with fused five-membered rings exhibit expanded aromatic and anti-aromatic circuits passing through the outer rim of the fused rings. The expanded aromatic and anti-aromatic circuits severely affect the electronic structures of the porphyrin derivatives.

A 10,20-bis(triisopropylsilylethynyl)tetrabenzo-5,15-diazaporphine (TIPS-TBDAP) was synthesized by the metal-template aza-annulation reaction. TIPS-TBDAP showed intense far-red fluorescence at 723 nm with a fluorescence quantum yield of 31% in chloroform solution. X-ray diffraction analysis revealed that TIPS-TBDAP forms a one-dimensional slipped $\pi$-stacking structure in the single crystal state. TIPS-TBDAP is soluble in common organic solvents owing to the bulky substituents and solution-processed field-effect transistors (FETs) could be fabricated. Dip-coating and single-crystal FETs showed the maximum hole mobilities of 1.5× 10${}^{-3}$ and 0.16 cm² V${}^{-1}$ s${}^{-1}$, respectively.

We have introduced trifluoromethyl groups into meta-positions of two meso-phenyl rings of a push-pull-type porphyrin dye (ZnP-CF${}_3)$ to modulate the energy levels of the porphyrin dye for dye-sensitized solar cells (DSSCs). The light-harvesting ability of ZnP-CF${}_3$ is almost comparable to those of reference porphyrins where the trifluoromethyl groups are replaced with methyl (ZnP-CH${}_3)$ or tert-butyl groups (YD2). We revealed that the introduction of the electron-withdrawing trifluoromethyl groups is effective to lower the excited-state oxidation potential of the porphyrin (–0.80 V vs NHE), which is consistent with the theoretical calculation. Meanwhile, DSSCs with ZnP-CF${}_3$ exhibited a lower power conversion efficiency ($\eta )$ of 5.95% than DSSCs with ZnP-CH${}_3$ ($\eta$ = 7.33%) and YD2 ($\eta$ = 8.97%) because of the severe aggregation tendency of ZnP-CF${}_3$ arising from the trifluoromethyl groups. In addition, the insufficient steric bulkiness of the trifluoromethyl and methyl groups relative to tert-butyl groups would result in the lower short circuit current and open circuit voltage for ZnP-CF${}_3$ and ZnP-CH${}_3$ due to fast charge recombination between electrons in the conduction band of TiO₂ and I${}_3^{-}$in the electrolyte solution. Overall, introducing both trifluoromethyl groups and bulky substituents into a porphyrin core would be necessary to boost cell performance.

Calix[3]pyrrole and its furan derivatives exhibited bathochromically shifted lowest-energy electronic transition bands in their absorption spectra compared with their calix[4]- and calix[6]-pyrrole analogues, despite the repeating units being the same. We also observed fluorescence emission for calix[3]-type macrocycles. The Stokes shift of the furan/pyrrole hybrid macrocycles, calix[2]furan[1]-pyrrole, and calix[1]furan[2]pyrrole, substantially varied depending on the solvent polarity. Non-covalent interaction (NCI) analyses indicated enhanced interactions between neighboring aromatic rings in the calix[3]pyrrole macrocycle, whereas such interactions were weak in calix[4]pyrrole, in which the interchromophore distance is remarkably longer than in calix[3]pyrrole. Theoretical analyses indicated that the red-shifted, lowest-energy bands of calix[3]pyrrole correspond to HOMO–LUMO transitions, the energy gap of which was narrow compared with calix[4]pyrroles. The characteristic absorption bands for calix[3]pyrrole and its related macrocycles are useful as probes for distinguishing such macrocycles from higher calix[$n$]pyrrole ($n\ge$ 4) analogues that exhibit almost identical absorption spectra.

A series of cis-difunctionalized 21-telluraporphyrins containing two functionalized meso-aryl groups such as $p$-iodophenyl, $p$-bromophenyl, $p$-cyanophenyl, $p$-nitrophenyl and $p$-trimethylsilyl ethynylphenyl groups in cis-fashion were synthesized by condensing one equivalent of 16-telluratripyrrin with two equivalents of functionalized benzaldehyde and three equivalents of pyrrole in CH₂Cl₂ under acid catalyzed porphyrin forming conditions. The cis-difunctionalized 21-telluraporphyrins were thoroughly characterized by HR-MS, 1D and 2D NMR, and absorption spectroscopic techniques. To show the use of cis-difunctionalized 21-telluraporphyrin building blocks, the covalently linked (BODIPY)₂-telluraporphyrin triad was synthesized by coupling cis-diiodophenyl 21-telluraporphyrin with meso-ethynylphenyl BODIPY under Pd(0) coupling conditions and afforded (BODIPY)₂-telluraporphyrin triad in 24% yield. The NMR and absorption studies of the triad indicated that the telluraporphyrin and BODIPY moieties interact weakly in the (BODIPY)₂-telluraporphyrin triad and retain their individual characteristic features. The steady-state fluorescence and DFT studies indicated a possibility of charge transfer between 21-telluraporphyrin and BODIPY units in the triad.

In this paper, we report the first examples of amphiphilic metal(II) complexes of 5,10,15,20-tetraaryl-5,15-diazaporphyrinoids (M-TADAPs) containing triethylene glycol (TriEG) or tetraethylene glycol (TetEG) auxiliaries. A common dipyrrin precursor substituted with TriEG or TetEG groups underwent metal-templated cyclization with zinc(II), nickel(II), or copper(II) acetate to afford the corresponding TriEG- or TetEG-appended M-TADAPs (M = Zn, Ni, Cu) as air-stable 19$\pi$-electron radical cations. These 19$\pi$-electron M-TADAPs were reversibly interconvertible with 20$\pi$-electron antiaromatic M-TADAPs and 18$\pi$-electron aromatic M-TADAP dications by redox reactions. The newly prepared M-TADAPs were basically amphiphilic, but their water solubilities varied considerably depending on the charge of the diazaporphyrin (DAP) ring and the number of ethylene glycol units. The neutral 20$\pi$-electron M-TADAPs were poorly soluble in water, whereas the 18$\pi$-electron M-TADAP dications were soluble in water. Cyclic voltammetry of all M-TADAP derivatives revealed 20$\pi$/19$\pi$-electron and 19$\pi$/18$\pi$-electron redox couples in both CH₂Cl₂ and H₂O with appropriate electrolytes. The addition of M$\prime$X (M$\prime$ = Li, Na; X = Cl, OH) or HCl to aqueous solutions of the M-TADAPs highlighted their reactivities with anions and changes in pH. When treated with M$\prime$X in H₂O, the 19$\pi$-electron M-TADAP radical cations underwent anion exchange but the 18$\pi$-electron Zn-TADAP dications were reduced to the corresponding 19$\pi$-electron species. Upon treatment with HCl in H₂O, the 19$\pi$-electron M-TADAP radical cations underwent one-electron oxidation of the DAP ring, and the resulting 18$\pi$/19$\pi$-electron abundance ratio increased with decreasing solution pH.

A dinuclear zinc complex was synthesized by the reaction of an open-ring hemiporphyrazine containing two terminal phenyl groups with zinc acetate dihydrate. Single crystal X-ray analysis revealed that the complex consists of two five-coordinated zinc ions and two open-ring ligands. The two phenyl rings in the zinc complex were found to be directed towards the benzene-ring side of the isoindoline moieties, which was in contrast to the metal-free compound with the oppositely-directed phenyl groups. The effects of metal insertion on molecular and electronic structures were investigated both experimentally and theoretically.

In this study, we have prepared new tripyrranes embedded with azulene bearing two meso-pentafluorophenyl substituents. They were obtained as diastereomers in high yield which were separated using conventional column chromatography. Their distinct solution structures were unambiguously confirmed by NMR and mass analysis. Our synthetic strategy is simple and straightforward due to the reactivity of 1,3-positions of azulene, which underwent Lewis acid-catalyzed condensation with pyrrole-2-carbinol. These diastereomers were further subjected to acid-catalyzed (CF₃COOH) condensation with pyrrole dicarbinol to afford the target N-confused azuliporphyrin (reduced form) in trace amount. However, we obtained the tris-meso-pentafluorophenyl substituted azulicorrole (AzCorA) as major product due to an unprecedented scrambling of the azulitripyrranes. The structural characterization of newly synthesized key precursors and macrocycles was done with the aid of high-resolution mass analyses, and ¹H and 2D NMR analyses. The single crystal X-ray structure obtained for AzCorArevealed that the azulene subunit is tilted by 34.03${}^{\circ }$ due to the steric congestion of inner-NHs.

Two $\beta$-substituted Pd(II) porphyrins, (PdTPP(NO${}_2)$Ph₂ and PdTPP(Ph)${}_4)$, were synthesized and characterized by various spectroscopic techniques, and their spectral and electrochemical redox properties were investigated with respect to PdTPP. The single-crystal X-ray structure of PdTPP(NO${}_2)$-Ph₂ revealed saddle-shape conformation of the macrocyclic core of porphyrin. DFT studies revealed nonplanar saddle shape conformation of PdTPP(Ph)₄ with an average deviation of $\beta$-pyrrole carbon atoms from the porphyrin mean plane ($\mathrm{\Delta }$C${}_{\beta }$ = ± 0.751 Å) and also 24 core atoms ($\mathrm{\Delta }$24 = ± 0.368 Å) as compared to PdTPP(NO${}_2)$Ph₂ ($\mathrm{\Delta }$C${}_{\beta }$ = 0.649 Å and $\mathrm{\Delta }$24 = ± 0.317 Å) due to more $\beta$-pyrrole substitution. Both PdTPP(NO${}_2)$Ph₂ and PdTPP(Ph)₄ exhibited 13-19 nm and 49-59 nm red-shift in the Soret and Q${}_{x(0,0)}$ bands as compared to PdTPP, respectively. PdTPP(NO${}_2)$Ph₂ exhibited a very high dipole moment (7.32 D) as compared to PdTPP(Ph)₄ (0.239 D) due to the “push-pull” effect of electron donor (phenyl) and acceptor (-NO${}_2)$ groups at the $\beta$-pyrrole positions of the macrocycle. The redox potentials of PdTPP(NO${}_2)$Ph₂ anodically shifted ($\mathrm{\Delta }$E = 0.2-0.4V) as compared to PdTPP and PdTPP(Ph)₄ due to the presence of $\beta$-phenyl groups and the strong electron-withdrawing effect of the nitro group. Hence the HOMO-LUMO energy gap of PdTPP(NO${}_2)$Ph₂ decreased by 0.20 V and 0.28 V as compared to PdTPP(Ph)₄ and PdTPP, respectively.

Subphthalocyanines (SubPcs) are peculiar porphyrinoid compounds, exhibiting an intense absorption in the visible region and a particular cone-shaped structure that gives rise to their characteristic reduced aggregation tendency, which makes them suitable photosensitizers for photodynamic therapy (PDT) applications. On the other hand, subphthalocyanine fused dimers (SubPc${}_2)$ are best known for their $\pi$-extended surface and strong absorption in the near IR region, while keeping a low aggregation tendency. However, they remain unexplored photosensitizers in this field. Herein, the synthesis and study of properties of several axially aryloxy substituted SubPcs and SubPc fused dimers are reported. The axial aryloxy groups additionally bear polar substituents that help increase the solubility of this family of intrinsically hydrophobic compounds in polar solvents. All synthesized SubPcs and SubPc₂ showed a good ability to generate singlet oxygen (¹O${}_2)$ in experiments carried out in THF. Although ${\varphi }_{\mathrm{\Delta }}$ values obtained with SubPc fused dimers were lower than those of the corresponding SubPcs bearing the same substituent, the results are encouraging considering their absorption maximum is centered in the therapeutic window.

Near-infrared (NIR) dyes are used in various applications such as organic solar cells and photodynamic therapy sensitizers. One example of a class of dyes, octa-arylthio-substituted phthalocyanines (Pcs), can effectively absorb NIR light above 800 nm. The substitution of the Pc’s peripheral sulfur effectively introduces extra functions without significant perturbation of the optical properties. However, the synthesis of phthalonitrile precursors containing various functionalized arylthio groups has been limited. Herein, we provide the three-component-type coupling reactions for synthesizing phthalonitriles with various functionalized chalcogen-aryl groups. Organometallic reagents were prepared from aryl halides, elemental chalcogen, and 3,6-bis(trifluoromethanesulfonyloxy)phthalonitrile can lead to functionalized phthalonitriles in a one-pot procedure. Commonly used methods were utilized to prepare the corresponding Pcs. This reaction can be extended to other group-16 elements, chemoselective organomagnesium, and organozincate reagents. The NIR absorption and fluorescence properties of Pcs were also revealed and rationalized under substitution effects.

Two porphyrin-based D-$\pi$-A structured dyes of SGT-026 and SGT-027 with different acceptor groups were synthesized and characterized for dye-sensitized solar cells. The structure of SGT-027was designed with a very strong acceptor unit of (5-(naphtho[1,2-c:5,6-c$\prime$]bis[1,2,5]-thiadiazolyl)benzoic acid) (NBTD), resulting in more red-shifted absorption bands and broader NIR absorption ability, but SGT-026 porphyrin with a weak acceptor unit of (2-(thieno[3,4-c]pyrrole-4,6(5H)-dionyl)benzoic acid) (TPD) exhibited a blue-shifted Q band absorption, compared to the reference SGT-021dye with a strong acceptor unit of (4-(benzo[c][1,2,5]thiadiazol-4-yl)benzoic acid) (BTD). The photophysical properties of these D-$\pi$-A structured porphyrin sensitizers depend on the degree of the intramolecular charge transfer character with the electron-withdrawing ability order of NBTD> BTD> TPD. The photovoltaic performances were evaluated using cobalt (II/III)-based redox electrolyte, SGT-027 reached a power conversion efficiency (PCE) of up to 7.5%, which was surprisingly inferior to the benchmark porphyrin sensitizer SGT-021 with a PCE of 10.9%, and a PCE of 5.9% was exhibited by SGT-026, under AM 1.5G sunlight. The optical, and electrochemical properties and DFT calculations were utilized to understand the cell performance difference between SGT-dyes.

Utilizing tetraphenylporphyrin (TPP), tetratolylporphyrin (TTP), tetramesitylporphyrin (TMP), and tetra-$p$-chlorophenylporphyrin (T$p$ClPP) as ligands, several five-coordinate high-spin $p$-toluenethiolate Manganese(II) complexes are isolated and studied by UV-vis, single-crystal X-ray and EPR spectroscopies. The crystal structures show noteworthy features including flexible axial $p$-toluenethiolate ligands and intramolecular C−H$\cdot \cdot \cdot$$\pi$ and $\pi$-$\pi$ interactions between ligands and porphyrin planes. All four products are further studied by X-band EPR on both solid and solution states at 4 K which confirmed the $S$ = 2/5 high-spin states. Temperature-dependent EPR and measurements with different equivalents of ligands are also reported for comparison. The work provides new references for the study of the active center of P450s and the biochemical reaction between cysteine residues and heme.

This work is devoted to studying the aggregation effect on the nonlinear optical (NLO) and charge transport (CT) properties of low-symmetry phthalocyanines bearing a cyclotriphosphazene moiety, a monomer, and clamshell-type bis-phthalocyanine. FE-SEM and AFM studies revealed ordered nanoaggregation in these compounds, represented as repeating objects of regular configuration, globules (340–480 nm), which contain small aggregates inside their cavity, similar to smoothed polygons (ca. 40 nm). Such specificity is not characteristic of other functionalized phthalocyanines, which we dealt with earlier. A new spectral method for estimating the aggregation threshold based on the change in extinction with increasing concentration of solutions was also implemented, and the effect of aggregation on optical limiting was demonstrated. The behavior of isomers and rotamers of bis-phthalocyanine in the presence of electric fields of various strengths was investigated with the DFT calculations, and that partially corresponds to the impact of laser radiation on molecules. It was shown that the unusual behavior of the trans-isomer in FF-DFT calculations is the reason for the worsening of the NLO and CT characteristics of bis-phthalocyanine, in which the macrocycles are strapped through a phosphazene spacer. An advanced method of multiparametric analysis has been implemented to evaluate the NLO and CT properties of the dyes in general.

$\pi$-Extended azacoronene has been synthesized via an S${}_N$Ar reaction using acenaphthopyrrole and octafluoronaphthalene utilizing successive Scholl reactions. Although the chiral conformers could not be isolated, the new azacoronene analog exhibited longer-wavelength absorption and reversible oxidation properties, which are characteristic of pyrrole-fused azacoronenes. When combined with the results of our DFT calculations, the experimental results indicate weaker global aromaticity than that of previously reported azacoronenes.

Two zinc phthalocyanine derivatives (ZnPc 1 and 2) carrying bulky 2,6-diisopro-pylthiophenoxy peripheral substituents have been synthesized and their performances as photosensitizers in photochemical hydrogen production evaluated. To examine the influence of the spacer on the performance of ZnPc 1 and 2, the carboxyl group has been linked to the macrocycle ring either directly or via the phenyl ring, respectively. The photocatalytic activities of ZnPcs (ZnPc 1 and ZnPc 2) as sensitizers of TiO₂ for hydrogen production were investigated in the presence of Pt. ZnPc 1 and ZnPc 2 sensitized TiO₂ produced 0.687 mmolg${}^{-1}$h${}^{-1}$ and 0.436 mmol g${}^{-1}$h${}^{-1}$ hydrogens, which also reached 3.986 and 2.091 mmolg${}^{-1}$ after 8h illumination, respectively, under visible light ($\ge$ 420 nm) irradiation. In addition, STH efficiencies of ZnPc 1/TiO₂ and ZnPc 2/TiO₂ were determined as 1.77% and 1.12%, respectively. ZnPc 1/TiO₂ exhibited 1.9-fold more photocatalytic hydrogen amount than ZnPc 2/TiO₂, and the hydrogen evolution performance of the photocatalyst in the presence of Pt enhanced to 3.021 mmol g${}^{-1}$h${}^{-1}$ and 0.911mmol g${}^{-1}$h${}^{-1}$ for ZnPc 1 and ZnPc 2, respectively.

The development of synthetic transmembrane anion transport systems is of considerable interest, not only for mimicking the functions of natural transmembrane proteins but also for practical applications. We have recently reported a porous organic cage, porphyrin box (PB(8)) having multiple windows surrounded by octyl chains as an iodide selective anion channel. Herein, we report the modulation of transmembrane transport of halides (${\mathrm{\text{Cl}}}^{-}$, ${\mathrm{\text{Br}}}^{-}$, and ${\mathrm{\text{I}}}^{-})$ by dynamic window size engineering of the cage with different alkyl chain lengths (hexyl PB(6), octyl PB(8) and decyl PB(10)). ‘Apparent’ transport rates were measured by the HPTS fluorescence assay, which shows a gradual decrease in the transport rate upon increasing the length of alkyl chains of PB. We calculate the transport rate per PB in order to make a fair comparison as the ‘apparent’ transport rate is proportional to the number of PBs embedded in the lipid membrane. The transport rate per PB reveals that increasing the length of the alkyl chains of PBs results in a substantial fall in the iodide transport rate while only marginally decreasing the transport rates of bromide and chloride, thereby decreasing the selectivity of iodide transport.

During the preparative investigation of $\pi$-expanded porphyrinoids based on the retro-Diels-Alder reaction of bicyclo[2.2.2]octadiene(BCOD)-fused precursors for benzo- and benzo[$k$]fluorantho[9,10]-[$b$]porphyrins by the [3+1] porphyrin synthesis using tripyrrane-1,14-dicarbaldehyde and BCOD-fused pyrroles, serendipitous formation of the corresponding corroles was observed. After elucidation of the reaction conditions, the [3+1] reaction afforded 21,31-dihydro-21,31-ethanobenzo[$k$]fluorantho[9,10-$b$]corrole in 23% yield as well as a trace amount of the corresponding porphyrin. In the sapphyrin synthesis by the [3+2] approach using the tripyrrane-1,14-dicarbaldehyde and a bipyrrole, the similar reaction conditions resulted in the formation of 5-pyrrolylcorrole in a 38% yield as well as isosmaragdyrin and the originally targeted sapphyrin.

A hexapyrrane P6 with a terminal N-confused pyrrole was synthesized by acid-catalyzed [3+3] condensation followed by oxidation with DDQ, which did not afford the expected N-confused hexaphyrin. In stead, a rearranged product, i.e., $\alpha$-dipyrrin appended N-confused porphyrin 1 was obtained in a yield of 46%. Chelation of 1 with Pt(II) afforded the peripheral complex 1-Pt, which was further coordinated with Rh(I) in the cavity to afford the corresponding bimetallic complex 1-Pt-Rh. Both 1-Pt and 1-Pt-Rh exhibit split Soret-like bands and noticeable Q-like bands tailing to the NIR region up to ca. 1200 nm. Single crystal X-ray diffraction analyses of 1 and 1-Pt revealed that the peripheral coordination of Pt(II) slightly modifies the interplanar angle between the porphyrin macrocycle and the dipyrrin unit, which may modulate the absorption spectra. The results of this work compose an interesting example of synthesizing porphyrinoids appended with conjugated peripheral chains by the oxidative ring closure reaction of an oligopyrrane containing a terminal N-confused pyrrole, and such compounds may be used for both inner and peripheral coordination to afford complexes with tunable NIR absorption.

Mixed boron,antimony-capped iron(II) tris-dioximate monoclathrochelates and their hybrid phthalocyaninatoclathrochelate derivatives, the molecules of which are decorated with the single N-donor 4-pyridyl group, were obtained using two different approaches, such as (i) a transmetallation (a capping group exchange) reaction of their antimony-capped macrobicyclic precursors, and (ii) the direct template condensation of the ${\mathrm{\text{Fe}}}^{2+}$ ion as a matrix. The obtained complexes were characterized using elemental analysis, ¹H and ${13}^{}$C{¹H} NMR, MALDI-TOF MS, and UV–vis spectra, and by the single-crystal X-ray diffraction experiments. Solution UV-vis spectra of 4-pyridyl-terminated iron(II) phthalocyaninatoclathrochelates can be described as a superposition of the spectrum of its metallocomplex precursor M^IVPc and that of the iron(II)-encapsulating semiclathrochelate fragment. As follows from the X-ray diffraction data for the hybrid hafnium(IV)-capped tris-dimethylglyoximate pthalocyaninatoclathrochelate and its macrobicyclic boron,antimony-capped precursor, their ${FeN}_6$-coordination polyhedra possess the geometry close to intermediate between a trigonal prism (TP) and a trigonal antiprism with the distortion angles $\varphi$ of 20–30^∘. Due to a non-equivalence of their capping fragments, it can be also described as a distorted truncated trigonal pyramid. ${ZrN}_4{O}_3$-coordination polyhedron in the hybrid complex possesses the geometry of a capped TP. 4-Pyridylboron-capped pthalocyaninatoclathrochelates are proposed as prospective monodentate N-donor 3D-ligands for the design of various clathrochelate-based coordination assemblies, polytopic and polynuclear systems.

Two novel phenylenes (1,4-phenylene and 4,4^′-biphenylene) bridged dimeric BOBPY (Boron complexed ${\mathrm{\text{N}}}_2$O-type benzopyrromethenes) were designed and synthesized from the one-pot condensation of pyrrole with formylisoindole and subsequent complexation with diboronic acid. These novel dyes were fully characterized by NMR spectroscopy, HRMS, absorption and fluorescence emission spectroscopy, and cyclic voltammetry. These resulting BOBPY dimers are highly photostable and show intense absorption and emission in the region of 618 to 644 nm with high absorption coefficients and solvent-dependent fluorescence quantum yields. The electronic interactions between BOBPY units are related with length of the linker. And the dimer with short 1,4-phenylene linker was more sensitive to the polarity of the solvents than that of the other dimer, suggesting that the short linkage allowed stronger electronic communication between the two BOBPY units.

Amphiphilic zinc(II) (1), nickel(II) (2), and palladium(II) (3) complexes of 1,4,8,11,15,18,22,25-octakis(1,4,7,10-tetraoxaundecyl)phthalocyanine were synthesized and characterized by elemental analysis and MALDI-TOF mass and ¹H NMR spectroscopies. Electronic absorption spectra showed aggregation of the phthalocyanine molecules in ${\mathrm{\text{H}}}_2$O for 2 and 3, while the monomeric form for 1 in ${\mathrm{\text{H}}}_2$O, and 1, 2, and 3 in ${\mathrm{\text{CH}}}_2{\mathrm{\text{Cl}}}_2$. The cyclic voltammograms of 1, 2, and 3 in ${\mathrm{\text{CH}}}_2{\mathrm{\text{Cl}}}_2$ showed that oxidation of the phthalocyanine ring occurs easily in these complexes. This may be due to the energetically increased HOMO, coming from the deformation of the phthalocyanine ring. Steric hindrance between the $\alpha$-introduced 1,4,7,10-tetraoxaundecyl groups (tri(oxyethylene) chains) within the phthalocyanine molecule gives rise to the deformation of the phthalocyanine ring, which decreases the aggregating nature of the present complexes.

The ease of functionalization of BODIPY dyes provides scope for preparing pH indicators by introducing suitable functional groups. In this work, two dimethylamino substituted BODIPY dyes 3 and 4 with styryl and phenylbuta-1,3-dienyl groups introduced at the 3,5-positions were synthesized, characterized, and studied for use as pH indicators. Incorporation of the electron-rich vinylene substituents yielded dyes that absorb in the NIR region with emission wavelengths of 796 and 797 nm for 3 and 4, respectively, in dimethylsulfoxide (DMSO). Time-dependent density functional theory (TD-DFT) calculations were performed to study the effect of adding an extra alkene bond in 4 on the photophysical properties. The extra alkene bond in 4 resulted in a 3 nm shift in the main NIR region absorption band, lower molar extinction coefficient values, higher emission wavelength, and a decrease in fluorescence quantum yield in all solvents studied. Upon protonation of the amino groups, a large blue shift is observed in both the absorption and emission wavelengths, along with an increase in the fluorescence quantum yields and longer fluorescence lifetimes. The $p{\mathrm{\text{K}}}_{\mathrm{\text{a}}}$ values for 3 and 4 were estimated to be 2.9 (± 0.05) and 1.2 (± 0.05), respectively.

Two new peripherally substituted with 4 and 8 electron-donating 4-methylthiophenyl silicon phthalocyanines, ${(\mathrm{\text{ArS}})}_4\mathrm{\text{SiPc}}$ 1 and ${(\mathrm{\text{ArS}})}_8\mathrm{\text{SiPc}}$ 2, axially substituted with carboxylic acids have been synthesized using microwave irradiation in a very good yield. The new compounds have been characterized by ¹H-NMR, UV-vis, fluorescence, differential pulse voltammograms, and HR-MALDI-TOF mass spectrometry. An study of the stability of the axial chlorinated SiPcs in the function of the number of thiophenyl substituents indicates than ${(\mathrm{\text{ArS}})}_8{\mathrm{\text{SiPcCl}}}_2$ 10 degradates faster, to its corresponding unreactive dihydrosilicon phthalocyanine derivative ${(\mathrm{\text{ArS}})}_8\mathrm{\text{SiPc}}{(\mathrm{\text{OH}})}_2$ 11, than ${(\mathrm{\text{ArS}})}_4{\mathrm{\text{SiPcCl}}}_2$. The new SiPcs are excellent candidates as photoactive linkers for the construction of MOF materials.

Tetra non-peripheral and peripheral substituted Zn(II) phthalocyanine (Pc) derivatives bearing 2,2-difluoro-2-[1,1,2,2-tetrafluoro-2-(trifluoromethoxy)ethoxy]ethoxy groups (KH-69, KH-71) were synthesized and characterized to be antioxidant and antimicrobial agents. Photo-physicochemical properties of these compounds were investigated. Then, the DPPH free radical scavenging activity of the Pc derivatives was found as 97.74% and 94.89%, respectively. Both the Pc complexes showed perfect DNA nuclease activity with double strain break against pBR 322 plasmid DNA at 100 mg/L concentration. KH-69 and KH-71 indicated good antimicrobial activity against studied Gram-positive and Gram-negative bacteria, and fungal strains. Moreover, the Pcs showed excellent cell viability inhibition activity even at the lowest concentration. These Pc derivatives inhibited P. aeroginasa and S. aureus biofilm formation. The Pcs showed the highest biofilm inhibition with photodynamic therapy against S. aureus and P. aeroginasa with 95.40% and 90.03%, respectively.

A flexible Zn(II)porphyrin dimer has been utilized as an efficient host for the selective binding of several diols and diamines as substrates. Stepwise formation of a 1:1 host-guest polymer and 1:2 host-guest monomer via intermolecular self-assembling and disassembling processes, has been demonstrated with a series of diamine/diols. Transfer of chirality from the molecular to the supramolecular level has been rationalized with structural elucidation. The formation of the 1:1 host-guest polymer displays a bisignate CD couplet. X-ray structure demonstrates the presence of both clockwise and anticlockwise conformers, however, the conformer formed as per pre-organization in the substrate chirality contributes more towards the overall CD couplet in solution. The addition of the substrate in excess leads to the inversion of the CD couplet due to the formation of the monomeric complex. Architectural selectivity has been illustrated for the 1:1 host-guest complexation by simply tuning the length of the substrates. Crystallographic characterizations revealed linear 1D polymeric structures for the 1:1 host-guest complexes with longer diamines while shorter substrates stabilize cyclic dimer via intermolecular H-bonding between the urea bridge (cis-NH-CO-) of the two porphyrin dimers. Interestingly, the molecular structure of 1:1 host-guest complexes with diols displays a linear polymer despite the shorter length of the substrates. Along with weaker coordination of the alcoholic oxygen towards the Zn(II) ion, the presence of bulky substituents at the coordinating sites of the diols renders the formation of intermolecular H-bonding interactions. Thus, the nature of metal ion and their binding affinity towards the substrate, host-guest size complementarity, and the bulk of the substituents contribute cumulatively towards the architectural selectivity. The cyclic dimers display larger upfield shifts of the substrate protons in the ¹H NMR spectra as compared to the linear polymers. Moreover, the computational calculations further substantiate the experimental observations.

Metal-free, magnesium, titanyl, and vanadyl tetrapyrazinoporphyrazines substituted with eight 2,6-diisopropylphenoxy groups at the peripheral positions were prepared and characterized by NMR, UV-Vis, magnetic circular dichroism (MCD), and mass spectrometry methods. In addition, the Pc^(2,6iPrPhO)8VO complex was characterized by EPR spectroscopy and X-ray crystallography. Reaction between TiCl₄ with 4,5-(2,6-diisopropylphenoxy)phthalonitrile in N,N-dimethylaminoethanol resulted in the formation of a red open-chain trimer, which was characterized by mass spectrometry and X-ray crystallography. Electronic structures of new compounds and their excited state properties were probed by Density Functional Theory (DFT) and Time-Dependent DFT (TDDFT) methods.

The arrays consisting of two BODIPY chromophores axially bound to a Sn(IV)Porphyrin via a phenolate bridge have been synthesized and characterized. Photophysical properties of obtained systems have been investigated in aqua medium with different viscosity due to the addition of glycerin. The fluorescence quantum yield of the triad upon excitation at different wavelengths, as well as its lifetime and singlet oxygen generation quantum yield in an excited state, has been determined. It has been shown that if in the triad composition the fluorescent properties of the BODIPY fragment are weakened in all studied media, then the fluorescent properties of the porphyrin fragment depend on the properties of the medium. Quenching of the BODIPY fluorescence and the porphyrin fluorescence enhancement in viscous media or increasing of the triad’s ability to generate singlet oxygen in water is the result of photo-induced electron transfer from the phenolate to the porphyrin fragment. The efficiency of electron transfer and, consequently, the efficiency of quenching depend on the conformational mobility of the ligandin the triad, i.e. on the relative position of the phenolic and indacene fragments, which gives the designed triad the properties of a fluorescent molecular rotor. The best efficiency of the triad as a fluorescence molecular rotor has been obtained in the low viscosity range from 1 to 4 cP.

We report here on the self-assembly of two components, a Zn(II) porphyrin substituted with four lipophilic cytidines and a linear linker substituted with two guanosines, into a Watson-Crick hydrogen-bonded tetragonal prism. The corresponding ensemble, comprising two cofacial porphyrin macrocycles, exhibited similar supramolecular behavior as a reference cyclic tetramer previously studied by us. The establishment of strong G:C interactions in apolar chlorinated solvents was demonstrated by the chemical shift recorded for the relevant H-bonded protons. Most importantly, the hexacomponent prism assembly, when partially dissociated by the addition of the competing DMSO solvent, exhibited a slow exchange on the NMR timescale with the individual constituents, which is characteristic of kinetically stabilized discrete assemblies. Absorption, emission, and CD spectroscopy experiments revealed that the spectral features of the tetragonal prism were totally different from the ones recorded for the porphyrin and linker components, which also showed strong self-aggregation in apolar solvents. Temperature-dependent experiments, monitored by NMR and optical spectroscopy techniques, revealed remarkable thermodynamic stability for the prism assembly.

The synthesis and biological studies of meso-functionalized BODIPYs (BD-1 and BD-2) are reported. A pharmacophoric group (2-methyl-4-nitro-$N$-phenylaniline) was introduced at the meso-position of the BODIPYs. The substitution resulted in the red-shifted emission from BD-1 and BD-2as compared to the parent meso-aryl BODIPY. Molecular docking studies on PARP (Poly ADP-Ribose Polymerase) protein indicated efficient binding affinity of BD-2(-5.287) compared to BD-1. The cytotoxicity studies on triple-negative breast cancer cell line (MDA-MB-231) showed excellent photodynamic behavior of both compounds. Compound BD-2 showed excellent anti-proliferative activity in light with an IC${}_{50}$ value of 38 nm. However, in the dark condition both the compounds exhibited non-toxic behavior with 75–80% cell viability. The bioimaging studies indicated the cytoplasmic distribution of BD-1 and BD-2in the breast cancer cells.

Green chemistry has emerged as a powerful tool to rationally design environmentally sustainable chemical processes by choosing safe chemicals and minimizing the production of waste. This article focuses on the opportunity, yet underexplored, to evaluate the green syntheses of phthalocyanines by means of metrics such as the E-factor and EcoScale, in a view to better assess their sustainability and provide insights on their viability with respect to standard procedures.

Bicyclo[2.2.2]octadiene(BCOD)-fused 5,15-diazaporphyrins were synthesized via a metal-template aza-annulation of dipyrrin-metal complexes as a soluble precursor of tetrabenzodiazaporphyrin. 10-Azacorrole copper complex with a meso-imine bridge was serendipitously obtained via the same reaction using dimethylBCOD-fused dipyrrin-copper complex.

Unsymmetrical phthalocyanines and related macrocycles are often desirable for covalent construction or the self-assembly of more complex architectures. Terminal alkynes are versatile in this regard because they are amenable to cross-coupling via Sonogashira-type reactions, alkyne-alkyne coupling via Glaser-type couplings, and triazole formation via Click reaction with azides. Here we describe two complementary syntheses to conveniently add a single alkyne onto the phthalocyanine peripheral position and onto the meso-phenyl group of an (aryl)tetrabenzotriazaporphyrin, here providing a remote link point that is insulated from the macrocycle.

Solvation-induced switching between staggered and gauche conformers of europium(III) triple-decker complexes with $n$-butoxy- and crown-substituted phthalocyanine ligands [(BuO)₈Pc]${}^{2-}$and [(15C5)₄Pc]${}^{2-}$was studied by UV-Vis and ¹H-NMR in toluene and chloroform media. The crown-substituted complex Eu₂[(15C5)₄Pc]₃ was conformationally invariant, adopting the staggered arrangement of adjacent ligands in both solvents. In contrast, in the case of butoxy-substituted complex Eu₂[(BuO)₈Pc]₃, the staggered and gauche forms were stabilized in toluene and chloroform, respectively. These conclusions could easily be drawn from the UV-Vis data. In contrast, a comparison of the ¹H-NMR spectra of the complexes in both solvents showed that the spectral manifestation of conformational switching was obscured by media effects, although some characteristic spectral patterns of each conformation could still be identified on the example of the complex with hexa-$n$-butoxy-15-crown-5-phthalocyanine ligands Eu₂[(BuO)₆(15C5)Pc]₃.

Isoindole-diimine, which can be obtained by bubbling ammonia gas into a solution of phthalonitrile derivatives in the presence of Na${}^{+}$ ion, is a final and best precursor for phthalocyanine synthesis. In this study, isoindole-diimine and various derivatives have been prepared without bubbling ammonia gas using in situ generated ammonia that was produced from formamide and a strong alkali such as NaOH and NaNH₂. A longer reaction time, higher temperature, and larger amount of formamide were required for phthalonitrile derivatives with electron-donating groups, but this method is recommendable in that an NH₃ gas cylinder and concomitant gas regulator, which are not inexpensive, are not required. Attempts were made to interpret the IR and absorption spectra of the resultant diimines. The signals due to imino proton or N-H of diimino compounds were experimentally found to appear at around 8.2$\sim$9.5 ppm in ¹H-NMR and ca. 3500–3000 cm${}^{-1}$ in IR spectra.

Investigation into the reactive oxygen species (ROS) generating abilities of photosensitizers outside of in-vitro/vivo conditions is a crucial element in the wider study of photodynamic therapy (PDT) in clinical settings. Zinc(II) phthalocyanine tetrasulfonic acid (ZnPcTS) is a water-soluble photosensitizer that can generate ROS as singlet oxygen (SO) under irradiation in the red and far-red region of the electromagnetic spectrum. The incorporation of ZnPcTS into nano-fibers of a bis-imidazolium hydrogel was demonstrated and the material was characterized with photophysical, rheological, and microscopy techniques. This supramolecular material containing ZnPcTS (named ZnPcTS_nEqBase@Gels) was found to significantly enhance the SO generation rate with respect to that of ZnPcTS in an aqueous solution. The effect is attributed mainly to reduced aggregation within the gel microenvironment compared with a solution. Furthermore, the preparation of ZnPcTS_nEqBase@Gels was carried out in the presence of varying amounts (0, 1, 2, 3, 4 eq.) of NaOH to improve the dissolution of ZnPcTSby ensuring full deprotonation of the sulfonate. The gel material containing 4 equivalents of NaOH per phthalocyanine was found to have a significantly greater SO-generating ability than the corresponding material containing no base. This phenomenon was shown to be partially a consequence of reduced aggregation as observed in the spectroscopic characterization. The enhancement in SO generation induced by this type of hybrid material makes it an attractive candidate to be used in different applications when efficient SO production is required.

Despite many notes about advantageous properties of Si(IV) phthalocyanines, their aza-analogues from the group of tetrapyrazinoporphyrazines (TPyzPzs) are only rarely reported in the literature, especially for macrocycles carrying peripheral groups. Thus, a series of Si(IV) TPyzPzs having alkylamino, aryloxy, alkylsulfanyl or alkyl group at the periphery was prepared by complexation of Si(IV) into corresponding metal-free derivatives by their stirring at 30${}^{\circ }$ C with trichlorosilane, using tributylamine as a base, and dichloromethane as a solvent. Key factors affecting the feasibility of this method, such as well-chosen excess of trichlorosilane and solvent used, were described. The model compound of the series ($i.e.$, aryloxy substituted dihydroxy Si(IV) TPyzPz) was then modified at axial positions using trihexylchlorosilane as a ligand. All target Si(IV) TPyzPzs showed strong absorption with Q-band maxima ranging 617–655 nm (extinction coefficients 82 000–341 000 L⋅mol${}^{-1}$⋅cm${}^{-1})$ and efficient fluorescence emission with ${\mathrm{\Phi }}_F$ values ranging 0.32–0.44 with the exception of alkylamino substituted TPyzPz, whose excited states were efficiently quenched by intramolecular charge transfer. The possibility of axial modification, good spectral and fluorescence properties as well as the ability to quench the excited states upon introduction of alkylamine groups indicate the suitability of these derivatives for fluorescence sensing applications.

The addition of ether functional groups to a metallophthalocyanine ring is known to significantly decrease the oxidation potentials of the ring. In this light, the impact of the branching of alkyl-ether groups on the electronic properties was investigated via the synthesis of non-peripheral ($\alpha )$-substituted n-butyl (1), iso-butyl (2) and sec-butyl (3) 1,4,8,11,15,18,22,25-octabutoxyphthalocyanines, in conjunction with Co and Cu metal centers. From 1 to 3 the first and second ring-based oxidation potentials were decreased by 70 mV and 110 mV respectively both for Cu and Co-containing complexes; the UV-visible Q-band maxima only changed by 4-8 nm, consistent with the destabilization of both the HOMO and LUMO, as confirmed by TD-DFT calculations. The reversibility of both redox couples was improved via branching (3) for the Co complexes. All six complexes were structurally characterized, with varying levels and types of ring distortions. All molecules show 1-D supramolecular stacking, but for n-butoxy 1Co an intermolecular Co-O interaction aligns the molecular stacks, while for sec-butoxy 3Co only $\pi$-$\pi$ stacking of the Pc-ring was present. Both 3Co and 3Cu were ring-oxidized at lower potentials than 1Co and 1Cu, and the increased steric bulk from the branched ether chains prevented the overlap of their N₈C₈ inner rings.

Under acidic conditions and at high ionic strength or in the presence of templating species, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS${}_4)$ self-organizes into J-aggregates. In these species, the porphyrins align in a general edge-to-edge geometry, responsible for their peculiar optical properties. The self-assembling process is hierarchical, and the kinetics are strongly dependent on the mixing protocols. In the case of sigmoidal profiles, the kinetic data have been treated using a model proposed in the literature by R.F. Pasternack. Accordingly, an autocatalytic growth with the formation of an $m$-mer of porphyrin units is the rate-determining step (RDS) leading to the eventual J-aggregates whose size spans from nano- up to the micro-scale. The impact of different experimental parameters, together with inorganic counter-anions, and various cationic and anionic species (organic anions, metal ions, porphyrins, and metal complexes) will be reviewed.

PorGal₈, a porphyrin conjugated with dendritic galactose units, binds to galectin-1 in bladder cancer cells and induces localized cell death after light activation. Although it has been previously shown that photodynamic treatment (PDT) affects the cytoskeleton of cancer cells, it is still unclear how this change contributes to PDT-induced cell death. In this work, the association between changes in the cytoskeletal constituents and cell death triggered by PDT with PorGal₈ was investigated in two bladder cancer cell lines derived from transitional cell carcinoma (UM-UC-3 and HT-1376 cells). Photoactivated PorGal₈ did not change $\alpha$-tubulin protein levels in UM-UC-3 cells but reduced $\alpha$-tubulin in HT-1376 cells. A significant decrease in vimentin protein levels was exhibited in both cell lines 24 hours after irradiation. In the initial post-irradiation stage, both cell lines showed changes in actin filaments, but only recovery was apparent in HT-1376 cells 24 hours after treatment. In cells expressing higher levels of galectin-1 (UM-UC-3), PDT did not significantly affect these protein levels. Interestingly, 24 hours after irradiation, there was a robust increase in galectin-1 levels in HT-1376 cells. A small GTPases family protein, RhoA, involved in the galectin-1 expression, was also evaluated, indicating an increase in HT-1376 cells 24 hours after therapy. Overall, our results bring new insights into the relationship between the phototoxic effects of PorGal₈ and the disorganization of the cytoskeleton. Clarifying the mechanisms underlying PDT efficiency might contribute to envisaging new potential therapeutic adjuvants for PDT, acting on the cytoskeleton, to treat resistant cancers.

Dye-sensitized photocatalytic systems (DSPs) have emerged as a promising strategy to achieve efficient and stable solar-driven H₂ evolution systems. In this work, we prepared and tested a series of zinc-trimesityl porphyrin carboxylic acid derivatives as photosensitizes in DSPs for H₂ evolution. In order to unveil the influence of the anchoring group, different positions of the carboxylic acid were studied. All porphyrins were adsorbed onto platinum-doped titanium dioxide nanoparticles (Pt-TiO₂ NPs) and were irradiated by a white LED source. The DSPs coated with Zn-TM(pCOOH)P(i.e. the carboxylic acid at the para-phenyl position) illustrated increased stability (2514 TONs for 1.0 × 10${}^{-5}$ M) and the highest H₂ evolution activity (1959 mmol g${}^{-1}$ h${}^{-1}$ for 1.5 × 10${}^{-4}$ M). These results reveal that efficient and stable DSPs for H₂ evolution can be developed by utilizing porphyrin derivatives as photosensitizers.

A hitherto unknown butadiyne-linked BODIPY dimer (4) has been synthesized under the conventional Glaser coupling reaction conditions using the ethynyl-substituted pyrrolyl-BODIPY (2) prepared by gold-catalyzed C-H alkynylation. Due to the $\pi$-extended structure of the BODIPY chromophore in 4, a characteristic broad absorption band in the near-infrared (NIR) region has emerged. Upon photoexcitation, the environment-dependent fluorescence spectral features were observed. The fluorescent response varied with solvents, viscosity, and temperature, which was found to originate from the conformational changes between the coplanar and twisted conformers in the otherwise rigid butadiyne-bridged dimer 4. Therefore, the BODIPY dimer 4 would be a potential NIR fluorescence material for use in the probes responding to the distinct viscous environment in biological tissues.

Since cancer is one of the leading causes of death worldwide, the development of new anticancer drugs has become important. Phthalocyanines (Pcs) as anticancer agents have attracted particular attention in recent years. Especially water-soluble sulfonated phthalocyanines have been used consistently for both the diagnosis and treatment of many different types of cancer, such as small lung tumors. Motivated by these facts, since the anti-cancer activity of sulfonated water-soluble cobalt phthalocyanine in prostate and breast cancer without photoactivation is not known before, we aimed to investigate the in vitro anti-cancer effectiveness (cyto- and genotoxic effect) of alpha-substituted water-soluble cobalt phthalocyanine (WS-CoPc) complex on prostate and breast cancer cells for the first time. For this purpose ROS production, cell death, and DNA damage levels, changes in nuclear and cell morphology, and the expression of apoptosis and ROS-related genes were determined. WS-CoPc exhibited anti-cancer effects with cytotoxic and genotoxic features in both prostate and breast cancer cells also the anti-cancer efficacy is more prominent in prostate cancer cells. Therefore our results demonstrated that this Pc has high cytotoxic and genotoxic effects, especially in prostate cancer cells in vitro and further studies are needed to reveal the current anticancer potential of this Pc without photoactivation.

$N$-bridged diiron porphyrinoid complexes are powerful oxidation biomimetic catalysts. Their use as oxidation catalysts is quite recent, as it started approximately one decade ago. Many mechanistic works and elucidation of properties are conducted on simple derivatives which are not functionalized, preventing their covalent incorporation into advanced materials, even though it would expand their scope of applications. With the ultimate purpose to produce $N$-bridged diiron porphyrinoid complexes that can be incorporated into advanced functionalized materials and thereby increase the range of their utilization, we have explored synthetic strategies to prepare di- and octafunctionalised $N$-bridged diiron porphyrin complexes, either with hydroxyl or propargyl functions, which have been selected for their versatility. The considerations taken into account for the synthetic strategies are detailed and the complexes are fully characterized.

The aggregative state of the Zn(II) tetra-spermine porphyrin derivative, ZnTCPPSpm4, has been investigated in the presence of different buffers at the same pH value: 5K (cacodylate) buffer, phosphate sodium salt buffer, and PBS. The photophysical characterizations (UV-vis, Fluorescence, and RLS) have indicated a precise self-assembly phenomenon depending on the buffered solution used. The porphyrin does not undergo a significant aggregation in 5K buffer, differently from what occurs in phosphate and PBS buffers. Here, the likely specific interaction between the phosphate molecules and spermine pendants leads to spontaneous porphyrin aggregation, as detected by the high fluorescence quenching, enhancement of the RLS signal, and a significant splitting of the porphyrin Soret band. As a result, the current paper aims to highlight the importance of the employed buffer throughout the experimental procedures performed in the presence of porphyrinoids.

New heterogeneous porous materials based on 5,10,15,20-(tetraphenyl)porphyrin (H₂TPP), 5,10,15,20-(tetra-N-methyl-4-pyridyl)porphyrin tetrachloride (H₂TNMPyP), zinc(II) 5,10,15,20-(tetra-N-methyl-4-pyridyl)porphyrin tetrachloride (ZnTNMP_yP), 5,10,15,20-(tetra-4-carboxyphenyl)porphyrin (H₂TCPP) and zinc(II)5,10,15,20-(tetra-4-carboxyphenyl)porphyrin (ZnTCPP) have been incorporated into mesoporous silica MCM-41 from slow diffusion of solutions containing different concentrations of porphyrin chromophores. Successful incorporation of all porphyrins has been confirmed by UV-Vis spectroscopy and TGA. XRD patterns of these silica-based host-guest samples prove that the mesoporous structure of MCM-41 remains unchanged after encapsulation. The potential abilities of these photosensitizers to form singlet oxygen (¹O${}_2)$ at the solid state/air interface after light excitation were investigated. Despite the variable amount of encapsulated porphyrin derivatives (based on UV-vis assessment and chemical analysis), the phosphorescence intensity of ¹O₂ peak at 1270 nm remains relatively the same from one composite to the other meaning that the photosensitizers are mainly placed at the surface of the MCM-41 particles.

The goal of this study was to develop mixtures of peripherally halogenated boron subphthalocyanines (BsubPcs) to explore these macrocycles as mixed alloys for applications within the organic electronic space. These halogenated BsubPc mixtures were synthesized by reacting mixtures of commercially available phthalonitriles, namely 4,5-dichlorophthalonitrile (Cl₂-pn), 4,5-difluorophthalonitrile (F₂-pn), tetrachlorophthalonitrile (Cl₄-pn), and tetrafluorophthalonitrile (F₄-pn), with boron trichloride (BCl${}_3)$ to achieve mixed halogenation upon formation of the BsubPcs. More specifically, as named, Cl₂-pn + F₂-pn and Cl₄-pn + F₄-pn mixtures were used to form Cl-Cl${}_{2\mathrm{\text{n}}}$F${}_{2\mathrm{\text{m}}}$BsubPc and Cl-Cl${}_{4\mathrm{\text{n}}}$F${}_{4\mathrm{\text{m}}}$BsubPc, respectively. To establish a firm synthetic methodology, the reaction kinetics of forming the BsubPc mixtures from their respective phthalonitrile mixtures were compared to the kinetics of the standard procedures forming the individual BsubPcs, for example, Cl-Cl${}_{12}$BsubPc from Cl₄-pn. As we use BCl₃ to form the BsubPcs, the axial bond is in general chloride, but we observed again random fluoride axial exchange, and therefore moved to the second step to have complete axial fluorination. Crude mixed halogenated BsubPcs were sublimed at high purities to enable physical characterization, including a study of UV-Vis absorption spectra differentiation, and cyclic (CV) and differential pulse voltammograms (DPV) electrochemical differentiation. We also did density functional theory (DFT) calculations for points of physical properties comparison. The comparison points are together with fully peripherally chlorinated Cl${}_{\mathrm{\text{n}}}$BsubPcs and fluorinated F${}_{\mathrm{\text{n}}}$BsubPcs. Given the outcomes, we foresee in future studies the ability to tune different ratios of peripherally halogenated BsubPc mixtures via synthetic tools, to enable tuning of the HOMO LUMO energy levels, which could consequently tune their application and performance in organic electronics.

Here, we present comparative experimental data and results of quantum chemical calculations (method MM+) describing electrostatic interactions of positively charged 5,10,15,20-(tetra-N-methyl-4-pyridyl)porphyrin molecules with negatively charged glutathione stabilized core/shell semiconductor quantum dots (QD) AgInS/ZnS leading to the formation of stable QD-porphyrin nanoassemblies in water (pH 7.5) at ambient temperature. Based on steady-state absorption/ photoluminescence, time-resolved experiments (TCSPC), and Raman spectroscopy, interface phenomena and changes in spectral properties for interacting subunits in nanoassemblies are analyzed. Using an elaborated size-consistent quantum chemical atomistic 3D model for glutathione stabilized AgInS/ZnS QD, we propose a detailed physico-chemical mechanism for the interaction of the porphyrin molecule with the QD surface. It includes electrostatic interactions of the positively charged porphyrin free base molecule with negatively charged capping ligand (glutathione), followed by a very fast metalation of porphyrin free base (formation of ligated Zn-porphyrin complex) which is directly fixed on the QD surface. These results highlight the complexity of interface processes in “QDs – porphyrin” nanoassemblies and provide valuable strategies for the detailed analysis of the excitation energy relaxation in the systems under study.

Nitration of 2,7,12,17-tert-butylporphycene, leading mainly to meso-substituted 9-nitro- and 9,20-nitro- derivatives, also yielded a small amount of porphycene bearing three tert-butyl moieties and the nitro group at the $\beta$ position. The electronic absorption spectra of 2-nitro and 9-nitroporphycenes are similar, but the photophysical characteristics strongly differ. Unlike the meso-substituted derivative, 2-nitroporphycene emits intense, long-lived (ns) fluorescence. Strong enhancement of fluorescence intensity is due to the absence of steric interactions between tert-butyl and nitro moieties. The two porphycenes also differ in their tautomeric properties. 2-nitroporphycene exists in one trans-tautomeric form, whereas two trans-tautomers of similar energies coexist in the meso derivative. These results are well reproduced by quantum-chemical calculations. The possibility of changing photophysics and tautomerism by shifting the position of the substituent may be exploited while designing porphycenes targeted for specific applications, such as photodynamic therapy or building molecular switches.

A molecular conjugate made of a free-base diphenyl porphyrin chromophore (DPP) trans-linked to two N-acridinium units has been synthesized and photophysically characterized in acetonitrile. Interestingly, the emission of both fluorophores is quenched in the array at room temperature. Steady-state and time-resolved optical analysis proved that an ultrafast electron transfer from the porphyrin to the acridinium units occurs upon excitation of either the porphyrin or the acridinium moiety. On the other hand, at low temperature (77 K) the emission of the porphyrin is completely recovered, thanks to the inhibition of the electron transfer, and a photoinduced energy transfer from the acridinium to the porphyrin component is observed.

The crystal structure of the indium(III) derivative of a chloro-substituted tetrapyrazinoporphyrazine (TPyzPz), which is dimerized through hydroxy bridges is reported. The In(III) ion resides well outside the mean plane of the distorted pyrazinoporphyrazine core and thus each TPyzPz fragment has a domed shape. Two axial hydroxy groups are coordinated to the indium ions of two adjacent In(III) tetrapyrazinoporphyrazine fragments to form a co-facial dimer (InTPyzPz) which are eclipsed in geometry. Each indium(III) is six coordinated and the whole molecule is neutral in charge. Four pyridine molecules are encapsulated between TPyzPz fragments in the dimer, thereby forming a stable host-guest system. The host-guest interactions between the TPyzPz and pyridines are achieved by efficient O-H...N and $\pi$...$\pi$ type nonbonding interactions. The packing pattern of the crystal shows that the InTPyzPz system formed a herringbone-type assembly in its network. A combination of multiple Cl...Cl, C-H...O, and C-...$\pi$ and interactions between adjacent TPyzPz have been observed which in turn favored and stabilized this supramolecular network. The dimeric InTPyzPz system is further studied by the Hirshfeld Surfaces analysis which also indicated significant nonbonding interactions in the crystal and the related 2D fingerprint plots provided a quantitative idea of the inter-atomic interactions among the adjacent dimers.

The construction of metallo-organic macrocycles using transition metals and optoelectronically active donor ligands is a very active area of research due to the potential applicability of these structures as sensors or as drugs for combined photodynamic/chemotherapy treatments. Herein, we report on the synthesis, photophysical properties, and aggregation behavior of a triangular Pt(II)-assembled metallo-supramolecular complex built by the coordination-driven assembly of a BODIPY functionalized with two pyridines at the 2,6 positions and an (R, R)-phenylalanine dipeptide moiety in the meso position. This hydrophilic group provides the metallacycle with water-solubility and self-assembly capabilities, which result in the formation of robust nanoparticles in aqueous solutions with a 50 nm average size.

The optical limiting properties of three meso-pyridyl-distyrylBODIPY dyes with differing alkyl substitution patterns at the 2,6- and 1,7-positions on the pyrrole moieties are investigated. Styryl groups are introduced at the 3,5-positions to form dyes with strong donor-$\pi$-acceptor (D-$\pi$-A) properties. Favorable optical limiting properties are obtained for all three dyes, with the highest second-order hyperpolarizability obtained for a dye that is unsubstituted at both the 2,6- and 1,7-positions suggesting that the optical limiting properties are enhanced when the meso-aryl ring can freely rotate into the plane of the BODIPY core.

Novel electron-deficient low-symmetry perhalogenated azaanalogues of subphthalocyanine, [Cl₂F₈N₂subPc] and [Cl₄F₄N₄subPc], were prepared by mixed co-cyclotrimerization of tetrafluorophthalonitrile and 5,6-dichloropyrazine-3,4-dicarbonitrile in p-xylene in the presence of BCl₃. They were characterized by MALDI mass-spectrometry, UV-VIS, IR, ${}^{13}$C, and ${}^{19}$F NMR spectroscopy, and the molecular structure of [Cl₂F₈N₂subPc] was established by single crystal X-ray diffraction. The spectral-luminescence and redox properties of [Cl₂F₈N₂subPc] and [Cl₄F₄N₄subPc] as well as peculiarities of their electronic structure are compared with the corresponding symmetrically substituted compounds - perfluorosubphthalocyanine, [F${}_{12}$subPc], and hexachlorotripyrazinosubporphyrazine, [Cl₆N₆subPc]. Consecutive substitution of one and two tetrafluorobenzene fragments by dichloropyrazine units leads to stabilization of the frontier $\pi$-molecular orbitals and widening of the HOMO–LUMO gap. As a result, electron-affinity of the macrocycle is increased and the first reduction potentials are increasingly shifted in the less negative region from -0.43 V for [F${}_{12}$subPc] to -0.31 V for [Cl₂F₈N₂subPc], -0.19 V for [Cl₄F₄N₄subPc], and the maxima of the Q-band is shifted hypsochromically from 573 nm to 565 and 553 nm, respectively. Preliminary photoelectrical measurements indicate that novel compounds can be used as acceptor materials in non-fullerene photovoltaic cells.

ABAB porphyrins are promising platforms for potential use in several applications, particularly in medical imaging. Herein, the synthetic optimization studies for preparing such porphyrins via the statistical condensation of 4-trifluoromethylphenyl and 1-methylimidazol-2-yl aldehydes with pyrrole, are described, with emphasis on the use of microwave irradiation as heating source, against conventional heating. Then, the preparation of the corresponding Mn(III) complex and cationization of the imidazole groups, using microwave irradiation, were also carried out and the photophysical, photochemical, and electrochemical properties were further assessed. The compounds revealed interesting features, including adequate log P, singlet oxygen yield, redox potentials, and excellent photostability, which pave the way for potential use as imaging probes in MRI or PET, or as photosensitizing molecules.

The replacement of cobalt in vitamin B${}_{12}$ derivatives by other transition metals is a formal path to non-natural corrins. Here, we describe nibinamide (Nibi), the novel Ni(II)-analogue of the natural B${}_{12}$-derivative cobinamide (Cbi), and its synthesis from the metal-free ligand of Cbi, hydrogenobinamide (Hbi), both isolated as tetrafluoroborate salts. Aqueous solutions of the metal-free corrin Hbi are strongly fluorescent, whereas its Ni(II)-complex Nibi is non-luminescent. The solution structures of Hbi and of Nibi were characterized by hetero-nuclear NMR-spectroscopy. The Ni(II)-corrin Nibi was deduced to be roughly iso-structural to cob(I)inamide (Cbi${}^I)$ and to house a diamagnetic d⁸-metal-ioniso-electronic to Co${}^I$ in Cbi${}^I$. The chemically robust Nibi is, thus, a structural mimic of enzyme-activated and reduced biosynthetic precursors of vitamin B${}_{12}$ and a B${}_{12}$-antimetabolite potentially functioning as a specific inhibitor of B${}_{12}$-biosynthesis.

Antimicrobial resistance is a matter of concern to all biological systems. This work investigates the antimicrobial activity of porphyrins conjugated to pristine graphene quantum dots (pGQDs) through non-covalent linking. A novel In 5,10,15,20-tetrakis[4-(benzyloxy) phenyl] porphyrin (InTBnOPP) was synthesized and fully characterized. The photophysicochemical parameters of H₂TBnOPP, ZnTBnOPP, InTBnOPP, and their conjugates were investigated. It was found that pGQDs improved the singlet oxygen quantum yield upon conjugation with the porphyrins. pGQDs-InTBnOPP had a higher singlet oxygen quantum yield of 0.80 when compared to all other conjugates. Porphyrins are well-known photosensitizers for photodynamic antimicrobial chemotherapy (PACT); this was also confirmed by pGQDs-ZnTBnOPP and pGQDs-InTBnOPP which completely inhibited both S. aureus and E. coli with log reduction values of 9.42 and 8.59 with an irradiated time of 5 and or 10 min, respectively. The porphyrins alone had significant antibacterial activities. In general, the obtained results demonstrate a good response of these nanoconjugates against Gram (+) and Gram (-) bacteria.

Transformation of organofluorine compounds by oxidation pathways is rare in chemistry and biology since C-F bonds formed by the most electronegative element should react with electron-deficient oxidizing species. Recently, we have shown that $\mu$-nitrido diiron phthalocyanine complexes efficiently catalyze oxidative defluorination of poly- and perfluoroaromatics by H₂O₂. Herein, we studied their more biologically relevant porphyrin counterpart, $\mu$-nitrido diiron(III,IV) tetraphenylporphyrin complex (TPP)Fe${}^{\text{III}}(\mu$N)Fe${}^{\text{IV}}$(TPP) in stoichiometric and catalytic reactions with a series of fluorinated aromatic compounds under oxidation conditions. The addition of hexafluorobenzene to (TPP)Fe${}^{\text{III}}(\mu$N)Fe${}^{\text{IV}}$(TPP) in the presence of $t$-butylhydroperoxide led to the formation of high-valent $\mu$-nitrido diiron(IV,IV) porphyrin cation radical complex [TPP)Fe${}^{\text{IV}}(\mu$ -N)Fe${}^{\text{IV}}$(TPP${}^{+•}$]F₂. This complex was isolated and its structural and electronic properties were investigated by spectroscopic methods (EXAFS, XANES, EPR, UV-vis). Replacement of ${}^t$BuOOH with H₂O₂ oxidant resulted in the catalytic defluorination of selected heavily fluorinated aromatic compounds with high conversions (25–84%), TON (1768–3535), and defluorination degrees (71–84%). The scope of oxidative defluorination with (TPP)Fe${}^{\text{III}}(\mu$N)Fe${}^{\text{IV}}$(TPP) was extended to perfluorinated olefins exemplified by perfluoroallylbenzene. The perfluorinated double bond was more reactive compared with perfluorinated aromatic moiety providing C₆F₅CF₂COOH and C₆F₅COOH products. The properties of $\mu$-nitrido diiron tetraphenylporphyrin in homogeneous and heterogeneous catalytic defluorination were compared with those of its phthalocyanine counterpart.

A series of porphyrinoids has been tested as sensing layers for the development of nanogravimetric chemical sensors using quartz crystal microbalances (QMB) as transducers. The macrocycles have been studied as Ni complexes, Cu in the case of corrole, to elucidate the influence of the molecular skeleton on the sensing properties of the related sensors. For the first time, subphthalocyanines have been tested in sensor applications. The study has been carried out by testing different volatile organic compounds chosen as model analytes. The results obtained demonstrate that the exploitation of different porphyrinoids offers useful insights for the development of cross-sensitive sensor arrays and can open novel perspectives for their applications in the sensor field.

This report describes the selective fluorometric detection of pyrophosphate in water with a simple Al${}^{\text{III}}$-salen complex. The Al-based probe is synthesized in two steps in 30% yield and disassembled in the presence of pyrophosphate into its molecular building blocks. The released 3-chlorosalicylaldehyde signaling unit leads to a detectable signal with a 29-fold increase in fluorescence (${\lambda }_{\text{em}}$ = 513 nm; ${\lambda }_{\text{ex}}$ = 388 nm). At this emission wavelength, we did not observe a response from the Al${}^{\text{III}}$-salen probe despite its intrinsic blue fluorescence (${\lambda }_{\text{em}}$ = 460 nm;${\lambda }_{\text{ex}}$ = 347 nm). The Al${}^{\text{III}}$-complex shows excellent discrimination of pyrophosphate over other ions including phosphate containing adenosine triphosphate, phytic acid, or glyphosate and only fluoride inhibits the pyrophosphate-triggered disassembly process. Related salen-based probes with the same hydrophobic ligand framework but either Zn${}^{\text{II}}$ or Fe${}^{\text{III}}$ ions instead of Al${}^{\text{III}}$ were not sufficiently robust and therefore not suitable for analytical applications in pure water at pH 7.4.

The ring size of tetrapyrrole ligands can dramatically influence the interfacial interactions of their metal complexes, as was found in a comparison of alkyl-substituted cobalt(II) porphyrins and cobalt(III) corroles adsorbed on a Ag(111) surface. The electronic properties of interfaces of both metal complexes were studied using photoelectron spectroscopy (XPS, UPS) and scanning tunneling microscopy (STM) in the monolayer and multilayer regimes. In the respective multilayers, the surface-decoupled complexes comprise paramagnetic cobalt centers, as indicated by the Co 2p core-level spectra. In the monolayers, both complexes are chemisorbed and engage in charge transfer at the interface. Consequently, the former singly occupied orbitals at the cobalt centers accept electron density from the Ag(111) surface. As a result, the cobalt centers of both complexes are reduced. Despite these similarities, there are substantial differences in the overall interaction strength: a much stronger interaction was observed in the case of the corrole complex, for which the interfacial charge transfer is not limited to the cobalt states, but also involves the ligand’s $\pi$-electron system. Density functional theory (DFT) calculations of the corresponding parent macrocycles reveal that, in comparison with the porphyrin, the corrole exhibits increased adsorption energy, a reduced adsorption height, and undergoes a stronger interfacial charge transfer. The increased stability of the corrole/ metal interface is attributed to the corrole ligand’s open-shell character with delocalized $\pi$-electron spin density and the resulting stabilization by rearomatization-driven electron transfer.

Expansion of porphyrin-like macrocycles can provide insights into the relationship between structural, optical, and electronic features. Here, we report the synthesis of a new nominally antiaromatic expanded porphyrin-like macrocycle (6) prepared via the condensation of 1,4-bis-(3,4-diethyl-2-pyrryl)benzene dialdehyde (4) with hydrazine. The absorption and emission features of this new macrocycle were compared to those of the parent bipyrrole-derived macrocycle, a system first reported in 1997. Attempts to oxidize both macrocycles (5 and 6) were unsuccessful, a failure ascribed to the steric limitations imposed by two substituents present on the $\beta$-positions on the di-substituted pyrrolic precursor. This stands in contrast to what was observed for the original bipyrrole system bearing only a single $\beta$-substituent on each of the pyrrolic moieties. The present results underscore the possible role of structure in governing electronic transitions in expanded porphyrins while highlighting the facility of hydrazine-based condensations in accessing readily large pyrrolic macrocycles.

The synthesis of a ruthenium(II) tetramer (Ru(L${}_{pc}$)${}_4$Cl${}_2)$ bearing pyridyl pentacene-based ligands and its corresponding model complex lacking pentacene moieties (Ru(L${}_{ref}$)${}_4$Cl${}_2)$ is presented. The formation of these tetramers is corroborated by ¹H, ${}^{13}$C NMR, and IR spectroscopies, as well as X-ray crystallography and mass spectrometry. Photophysical properties of the tetramers are probed by steady-state and time-resolved transient absorption spectroscopy. Steady-state absorption and fluorescence assays suggest weak ground-state interactions between the pentacene moieties of Ru(L${}_{pc}$)${}_4$Cl${}_2$ and sizeable metal-to-ligand interactions, which are ruthenium-to-pentacene based. Time-resolved transient absorption measurements reveal an ultrafast singlet-to-triplet transition that occurs on the femtosecond timescale and that yields vibrationally hot and solvent unrelaxed triplet excited states. After relaxation, these triplet excited states deactivate back to the ground state in less than 3 $\mu$s. These observations lead us to conclude that intersystem crossing outperforms photophysical processes such as singlet fission.

A conjugated planar dicobalt binuclear phthalocyanine 2CoCo exhibits extremely high catalytic activity in the oxidation of a thiol to the corresponding disulfide. Therefore this complex is interesting in the petroleum industry for the desulfurization of petroleum fractions. It is now necessary to study the reason and mechanism of the high activity of the cobalt complex. We describe the synthesis of different monocobalt binuclear Pcs 2CoM${}^2$ where the second Pc ring with M${}^2$ is either metal-free or metalated with Zn(II) or Ni(II) which were found to be redox-inactive in their Pc complexes. Then the catalytic activities of these heterometallic binuclear complexes are compared with the activity of the binuclear 2CoCo. Further, the activity of the mononuclear 1Co is considered for comparison. On the basis of the data obtained, it can be decided whether the high catalytic activity of the binuclear 2CoCo is a result of a cobalt-cobalt electronic exchange or a $\pi$-system extension.

First-row transition metal complexes derived from corrole-based ligands are considered efficient catalysts for hydrogen evolution reaction (HER). They are known to enhance the rate of hydrogen production by lowering the energy barrier in the water-splitting process. Here, the synthesis and characterization of a copper corrole complex (CuN2CA) having amine functionality on corrole has been reported. This complex is immobilized onto reduced graphene oxide (CuN2CA-rGO) that exhibited excellent electrocatalytic activity towards hydrogen evolution reaction (HER) with a significantly lower onset potential of -0.57 V vs. NHE efficiency of the corrole complex has significantly been improved when combined with reduced graphene oxide (rGO).

Porphyrin (Por) dyes are considered photoactive entities with potential properties to be applied as photosensitizers (PS) in cancer Photodynamic Therapy (PDT). The use of suitable units, like pyridinium ones, is an important strategy to add peripheral and non-peripheral positive charges in the Por structure, and in that way develop effective cationic PSs for melanoma treatments. In this context, free-base porphyrins bearing thiopyridinium (1) or methoxypyridinium (2) units were studied on melanoma cells, and their PDT effectiveness was studied and compared. The different charge positions of the cationic peripheral units on the Por macrocycle contribute differently to their PDT behavior. The obtained results demonstrate high in vitro PDT efficacy for both PSs. For the highest PS concentration tested (20 $\mu$M) the photocytotoxicity reaches the detection limit of the MTT assay upon 201 seconds of blue light irradiation ($\lambda$ = 405 ± 20 nm) at an irradiance of 24.9 mW/cm², which corresponds to a light dose of 5 J/cm². Interestingly, under the same experimental conditions, cationic Por 1 shows very interesting PDT results at lower concentrations of 1 to 10 $\mu$M.

Developing electrocatalysts with high activity and selectivity for the oxygen reduction reaction (ORR) has attracted increasing interest in the past decades. The many imidazole residues located at the active site of cytochrome c oxidases (CcOs) play crucial roles in facilitating the selective reduction of dioxygen to water. As inspired by nature, we herein reported on the synthesis of ${\mathrm{\text{Co}}}^{\mathrm{\text{III}}}$ corrole 1 hanged with a biologically relevant imidazolium group and its electrocatalytic ORR features in both acidic and alkaline solutions. Complex 1 is more active and selective than its imidazolium-free analogue for electrocatalytic four-electron ORR. Importantly, 1 displayed ORR activities with the half-wave potentials at $E_{1/2}$ = 0.65 V versus RHE in 0.5 M ${\mathrm{\text{H}}}_2{\mathrm{\text{SO}}}_4$ solution and at $E_{1/2}$ = 0.81 V versus RHE in 0.1 M KOH solution. This work presents a strategy to simultaneously improve catalytic ORR activity and selectivity by hanging a cationic imidazolium unit over molecular catalytic sites.

Combined therapy is currently a popular method for increasing the efficiency of antitumor treatment. It involves the use of two different tumor treatment methods, namely, chemotherapy and PDT. Combining a cytotoxic agent and a photosensitizer in a single molecule results in a synergistic antitumor effect that overcomes the multiple drug resistance and reduces the therapeutic drug doses. In this work, pyridine-containing natural chlorins were obtained by introducing a pyridine group into 13¹-$N$-(4-aminobutyl)amide of chlorin $e_6$ and its bacteriochlorin analogue, $O$-propyloxime-$N$-propoxybacteriopurinimide as well as $N$-aminobacteriopurinimide methyl ester. Moreover, a terpyridine residue was introduced as an external chelating moiety into $N$-hydroxypurpurinimide and $N$-aminobacteriopurinimide, and platinum complexes of all the above photosensitizers were obtained. The interactions of the latter with DNA were simulated and the lead compound, the platinum complex of pyridine derivative 13¹-$N$-(4-aminobutyl)amide chlorin $e_6$, which may become a potential agent for combined photodynamic and chemotherapy in oncology, was selected. The ability of the compounds obtained to manifest photodynamic and chemocytotoxic effects on tumor cells of various genesis was shown.