Journal of Porphyrins and Phthalocyanines

Metal phthalocyanine complexes with different charges, hydrophobicity and metal ions were synthesized and studied for antimicrobial photodynamic therapy of pathogenic bacterial and fungal model strains. Ten positively charged complexes with the metals Zn(II), Al(III), Ga(III), In(III), Si(IV) and Ge(IV) in the center of the ligand and substituents at the ligand bearing four or eight N-alkylpyridyloxy groups were prepared. In addition, a negatively charged Zn(II)-phthalocyanine with four sulfophenoxy-groups was synthesized. The absorption spectra showed low intensity of the Soret band in the UV part of the spectrum and the intense Q-band in the red to far red region (λ = 671–697 nm). The fluorescence was determined with quantum yields between 0.1–0.33 and life-times 2.8–4.9 ns in dependence of the kind of metal ion and the substituents. In organic solvents all complexes exist in a monomeric state but in aqueous solution they show aggregation with the exception of Ga(III) phthalocyanines. The singlet oxygen quantum yields were evaluated in dependence on the metals, substituents and the media with values between 0.16–0.68. The cationic metal phthalocyanines were taken-up by pathogenic cells in a higher amount as compared to the anionic complex. Three of the studied phthalocyanines namely tetra-N-methylpyridyloxy-phthalocyanine Zn(II) and tetra- and octa-N-methylpyridyloxy- Ga(III) phthalocyanines showed a high photodynamic efficacy towards most of the studied microorganisms in suspensions.

This work reports on the axial coordination of zinc phthalocyanine and bis-(1,6-hexanedithiol) silicon phthalocyanine to silver and gold nanoparticles. Red shifting of absorption spectra of the phthalocyanine complexes was observed after conjugation with the nanoparticles. An improvement in the photophysicochemical behavior and antimicrobial activity was achieved in the presence of metal nanoparticles for both complexes. A decrease in triplet lifetimes was observed for all the phthalocyanine metal nanoparticle conjugates. The Zn phthalocyanine complex gave the highest triplet and singlet oxygen quantum yield in the presence of gold nanoparticles. On the other hand, the bacterial inhibition was found to be best for the Si phthalocyanine derivative in the presence of nanoparticles compared to the Zn phthalocyanine counterpart. The highest antimicrobial activity was achieved for both conjugates against B. subtilis compared to S. aureaus both in the dark and under illumination with light.

Emission-based oxygen sensing properties of highly luminescent tetraphenylporphyrin molecules were investigated in polystyrene, ethyl cellulose, poly(1-trimethylsilyl-1-propyne) and poly(isobutylmethacrylate) matrices. The effect of perfluorochemicals (PFCs) on oxygen sensitivity and stability of the sensor materials was also examined. Fluorescence intensity and lifetime measurements of meso-tetraphenylporphyrinato Zn(II) (ZnTPP) and meso-tetraphenylporphyrin (H₂TPP) materials were performed in the concentration range of 0–100% pO₂. The fluorescence intensity variation of H₂TPPvs. oxygen was 86%. H₂TPP-based composite also yielded higher Stern–Volmer constant, faster response and regeneration time, excellent long term photostability and larger linear response range with respect to ZnTPP. The detection limit of oxygen for H₂TPP was less than 0.5%. When stored in sealed bags protected from sunlight, no decrease in oxygen sensitivity was observed during approximately five months. As far as we know, the gathered utilization of PFCs and H₂TPP embedded in polymer matrices was not previously described in literature, and has present amelioration compared to materials already existing.

The β-nitration reaction carried out on the corrole macrocycle has been shown to be extremely regioselective, although the reduced symmetry of the macrocycle could potentially lead to a huge number of possible regioisomers. We recently reported that the careful use of AgNO₂/NaNO₂ as a nitrating system enabled the achievement in good yields of mono- and dinitro-derivatives on both corrole free base and its copper complex, proving to be an efficient and cost-effective method. In this work, we present a detailed study of the scope of this method using TtBuCorrH₃ as a model corrole. A further increase of the oxidant pushes the nitration up to the functionalization of three β-pyrrolic positions, although concomitant decomposition of the macrocycle is also observed. The application of the proven nitration method with a five-fold excess of both silver and sodium nitrites with respect to corrole, afforded the 2,3,17-(NO₂)₃-TtBuPCorrCu as the main product, in 25% yield, together with traces of another compound identified by X-ray crystallographic analysis as the 3,8,17-(NO₂)₃-TtBuPCorrCu isomer. In light of these recent results, we also reinvestigated the characterization of the nitration products obtained from bis-substitution reactions, allowing among others the identification of the copper 3,8-(NO₂)₂ corrolate.

Dissociation of imino proton(s) in the cavity of the macrocycle of a highly water-soluble, metal-free phthalocyanine (H₂(H₄tsppc); where H₄tsppc denotes tetrakis{(2′,6′-dimethyl-4′-sulfonic acid)phenoxy}phthalocyaninate) in ethanolic and aqueous solutions has spectrophotometrically been investigated. The spectral changes associated with reaction with NaOH have been found to involve one-proton transfer process in aqueous media while two-protons process in ethanolic media. The acid-dissociation constant of the first imino proton in water (in the presence of Triton X-100) has been determined to be 12.5 ± 0.2 (as pKa) at 25 °C. The doubly deprotonated species in EtOH has been easily converted to its corresponding cobalt(II) derivative by thermal reaction with anhydrous CoCl₂.

In this work, the investigation of structural features, spectral and electrical properties of spin-coated films of substituted lutetium bisphthalocyanine Lu(Pc(SR)₈)₂, where R = -C₆H₁₃ was carried out. The current-voltage characteristics of ITO/Lu(Pc(SR)₈)₂/Al film sandwich structures were measured over the temperature range 120–380 K. AC electrical properties, mainly the dependence of conductance and capacitance on frequency and temperature are also discussed. Structural and electrical properties of anthracene-doped Lu(Pc(SR)₈)₂, films have also been investigated. Furthermore, optical properties of thin films of pure and anthracene-doped Lu(Pc(SR)₈)₂ films were also studied using spectroscopic ellipsometry, while atomic force microscopy (AFM) was used to study changes in films' morphology of doped films and compared with that of undoped films. Doping Lu(Pc(SR)₈)₂, films with anthracene is shown to lead to an increase in films' conductivity. These studies will provide full understanding of the physical properties of the Lu(Pc(SR)₈)₂, thin films, both doped and undoped, with the aim of exploitation in electronic device applications, such as fabrication of all organic solar cells.

Although tungsten porphyrins are known as mimicking models in biology, only a few papers about its chemical properties have been reported, the rarity of studies being attributed to the difficulties encountered in their synthesis due to their low stability. In this paper 5,10,15,20-tetra-p-phenyl-porphyrin tungsten(VI) chlorine (TPPWCl₄) was studied, this metallo-porphyrin characterized by different analytical techniques: UV-vis, FTIR, ESR, mass spectrometry, including photophysical determination of its singlet oxygen quantum yield, too. Its photodegradation reaction with the mechanism and species involved into this destruction reaction processes is discussed, too. Also, in order to maintain its photostability, TPPWCl₄ has been incorporated into solid substrates, such as ZnO and TiO₂, and these composites were subsequently tested in the photooxidation reaction of isoamylenes (2-methyl-2-butene and 2-methyl-1-butene mixture).

The synthesis and characterization of novel metal-free and metallophthalocyanines, fused symmetrically in non-peripheral positions with four octaoxamacrocycle has been synthesized by cyclotetramerization of the 2,5,8,11,14,20,23,26,29,32-decaoxatricyclo [31.2.2.1^15,19]octatriconta-1(36),15,17,19(38),33(37),34-hexaene-34,35-dicarbonitrile (5) which was prepared by the reaction of 3,6-bis[2-(2-{2-[2-(toluene-4-sulphonyl)-ethoxy]-ethoxy}-ethoxy)-ethoxy]-phthalonitrile (3) and 1,3-dihydroxybenzene (4). The novel compounds were characterized by using elemental analysis, ¹H, ¹³C NMR, IR, UV-vis and MS spectral data.

New phthalonitrile (L1), metal-free phthalocyanine (H₂Pc) and zinc-phthalocyanine (ZnPc) substituted in peripheral positions with 2-pyridyl methyl pendant arm linked mixed donor macrocyclic ligands have been prepared in a multi-step reaction sequence. The novel compounds were characterized by a combination of elemental anlaysis, ¹H NMR, ¹³C NMR, IR, UV-vis and MS spectral data. The influence of metal cations such as Cd²⁺, Zn²⁺, Hg²⁺, Al³⁺, Fe³⁺ and Cu²⁺ on the spectroscopic properties of dinitrile compound L1 and free phthalocyanine H₂Pc was investigated by means of absorption spectrophotometry. Spectrophotometric titrations were carried out with these ligands for Cu²⁺ ion. The complex composition of Cu-L1 was found 1:1 by means of spectrophotometric titration data. The spectrophotometric method showed good sensitivity for Cu²⁺ with linear range of 2.6 × 10^-6 to 1.3 × 10^-4 M with dinitrile compound.

Magnetic circular dichroism (MCD) spectroscopy and TD-DFT calculations are used to analyze the electronic structure and optical properties of an alkyl-substituted naphthalene-ring-bridged coplanar binuclear phthalocyanine dimer. An analysis of the MCD spectrum of the naphthalene-ring-bridged dimer relative to those of benzene-bridged compounds reported previously, demonstrates that there is a significantly weaker interaction between the two phthalocyanine rings. TD-DFT results obtained using the B3LYP functional with 6–31G basis sets were found to be problematic. Closer agreement with the experimental data is obtained when the CAM-B3LYP functional is used instead. The naphthalene-ring-bridged compound is found to be unsuitable for use as a photosensitizer for the formation of singlet oxygen, because the Φ_T values are negligible.

A non-covalent supramolecular complex combining porphyrin (Por), phthalocyanine (Pc) and fullerene [C₆₀], was obtained through zinc metal-pyridine coordination between a covalently meso-linked heterodimer ZnPor-ZnPc (4) and a N-pyridylfulleropyrrolidine derivative (5). The complexation was studied in toluene by absorption and fluorescence binding studies, and evidenced that the coordination of the N-pyridylfulleropyrrolidine (5) occurs preferentially through the zinc ion center of ZnPc (log K > 6.0) rather than ZnPor (log K = 5.23). Steady-state and time-resolved spectroscopies evidenced that upon selective excitation of either the Por, or the Pc moiety in [(ZnPor-ZnPc)∪C₆₀], the singlet excited state of Pc was generated efficiently in both cases (either from singlet-singlet energy transfer from ¹Por* to Pc, or directly after selective excitation of the Pc moiety). Next, an electron transfer occurred from the ¹Pc* to the C₆₀ to generate the charge-separated specie [(ZnPor-ZnPc^•+)∪C₆₀^•-]. Finally, the back electron transfer afforded the Pc triplet excited state rather than the ground state. The introduction of a covalent meso-linkage between Por and Pc in the heterodimer 4 and in the supramolecular assembly 4∪5 induces appreciable differences toward the photo-induced processes and the binding constants in comparison with other β-covalently linked analogue systems.

The preparation of some peripherally substituted (2,3,9,10,16,17,23,24) and non-peripherally substituted (1,4,8,11,15,18,22,25) octaalkyl lead(II) phthalocyanines with different alkyl chain lengths (6, 7, 8 or 9 carbons) is described and a comparison of some of their properties reported. X-ray structure analyses of the isomeric peripheral and non-peripheral octakis(octyl)phthalocyaninato lead(II) compounds reveal a greater degree of distortion of the ligand ring system from planarity in the former derivative. The series of peripherally substituted octaalkyl lead(II) phthalocyanines exhibit columnar liquid crystal behavior whereas the non-peripherally substituted isomers do not. The lability of the lead ion was investigated using ¹H NMR spectrometry under a specific set of conditions (8.8 × 10^-4 M solutions of the phthalocyanine in d₈-toluene containing d₄-acetic acid 2.06 × 10^-5 M). All the compounds underwent acid catalyzed demetalation at rates dependent upon the location of the substituents and, more surprisingly, the chain length of the alkyl groups. Under these conditions the lead ion within each of the peripherally substituted octaalkyl lead phthalocyanines was more labile than that in the non-peripherally substituted isomer.

Carbonaceous electrodes of dilithium phthalocyanine were prepared using graphite, carbon microspheres and multiwall carbon nanotubes. The electrochemical behavior of the dilithium bisphthalocyanine electrodes was found to be dependent on the nature of the carbonaceous material and on the nature of the electrolytic solution. The electrocatalytic properties of the dilithium phthalocyanine electrodes for oxidation of ascorbic acid were evidenced by the enhancement of the oxidation peak current, (~10 fold compared to the bare carbon electrodes) and the decrease of the oxidation potential at which oxidation of ascorbic acid takes place. The combined use of multiwall carbon nanotubes and dilithium phthalocyanine produces a synergistic effect that improves the electrocatalytic effect towards ascorbic acid.

The challenging task in the photodynamic therapy is the optimization of the procedure in a way to reach maximal selectivity of the phototoxic effect to tumor vs. non-neoplastic cells. The present study explores the impact of the light exposure with harmless UV 365 nm and low intensity visible red 637 nm light during incubation period on the uptake, primary localization, re-localization and photocytotoxic effect of tetra-galactopyranosyl substituted Zn(II) phthalocyanines. The studies were carried out on cancer cells (MDA-MB-231) and on non-tumorigenic cells (Balb/c 3T3, clone 31). The experimentals suggested that in addition to the favorable chemical structure of the applied amphiphilic protected galactose Zn(II) phthalocyanines, the pretreatment with UV 365 nm and visible red 637 nm light applied prior therapeutic light, lead to selective phototoxic effects on tumor cells.

The synthesis of novel, symmetrical zinc(II) phthalocyanine (ZnPc) bearing four ethynylcyclohexyloxy terminal moieties was achieved by cyclotetramerization of novel 4-(2-ethynylcyclohexyloxy) phthalonitrile in pentanol in the presence of DBU and zinc acetate without any protective/deprotective chemistry. Subsequently, this new zinc(II) phthalocyanine derivative was reacted with 6-azido-hexanoic acid under "click-chemistry" conditions to give phthalocyanine-hexanoic acid conjugates linked by 1,2,3-triazole units. The new compounds have been characterized by using elemental analyses, UV-vis, FTIR, ¹H NMR and mass spectroscopic data. The aggregation properties of the compounds were investigated in different concentrations. General trends are also described for fluorescence quantum yields and lifetimes of novel zinc derivatives in tetrahydrofuran. The fluorescence of the tetrasubstituted zinc(II) phthalocyanine complexes is effectively quenched by 1,4-benzoquinone (BQ) in THF.

The synthesis of tetra and octa 2,2,3,3-tetrafluoropropoxy substituted oxo-titanium phthalocyanines (TiOPc) are reported. Using strongly chelating oxygen donor ligands, the reactions of TiOPc with catecholate (1a, 2a), 4-nitrocatecholate (1b, 2b) and caffeic acid (1c, 2c), ellagic acid (1d, 2d) and chlorogenic acid (1e, 2e) are described. The new compounds were characterized by mass, ¹H NMR, FT-IR, and UV-vis spectroscopic techniques as well as elemental analysis.

The synthesis of tetra and octa perfluoroalkyl substituted zinc and metal free phthalocyanines (ZnPc and H₂Pc) are reported. The compounds 1–5 have been prepared by nucleophilic substitution of 4-nitrophthalonitrile with 1H,1H,2H,2H-perfluorooctanethiol, 1H,1H,2H,2H-perfluorodecan-1-ol, 1H,1H-perfluorodecan-1-ol, 1H,1H-perfluorotetradecan-1-ol and 1H,1H-perfluoro-3,6,9-trioxatridecan-1-ol, respectively. The compounds 6–8 have been prepared by the reaction of 1H,1H,2H,2H-perfluorodecan-1-ol, 1H,1H-perfluorodecan-1-ol and 1H,1H-perfluoro-3,6,9-trioxatridecan-1-ol with 4,5-dichlororphthalonitrile, respectively. The compound 9 with thia-bridge has been synthesized from 4,5-dichlororphthalonitrile. Zinc and metal free phthalocyanines were obtained from the corresponding phthalonitrile derivatives. All compounds were characterized by using mass, ¹H, ¹⁹F NMR, UV-vis and FT-IR as well as elemental analysis. Tetra substituted Zn(II) phthalocyanines are slightly soluble only in THF (Compound 4a and 7a are insoluble) but metal free phthalocyanines are not soluble. Octa substituted Zn(II) and metal free phthalocyanine are soluble in polar solvents such as THF and DMSO.

The novel 2,3,9,10,16,17,23,24-tetra-(15-crown-5)phthalocyaninato indium(III) hydroxide [(15C5)₄Pc]In(OH)(I) was obtained by direct interaction of tetra-(15-crown-5)-phthalocyanine with indium acetylacetonate with 90% yield. The set of UV-vis, ¹H NMR and MALDI-TOF spectroscopy data allowed the unambiguous interpretation of complex structure. It was shown that the developed synthetic approach can be also used for synthesis of indium(III) 2,3,9,10,16,17,23,24-octabutoxyphthalocyanine [(BuO)₈Pc]In(OH)(II). Photophysical characteristics (fluorescence and singlet oxygen quantum yields) of I were established. The photochemical stability of I was compared with tetra-(15-crown-5)-phthalocyanine H₂[(15C5)₄Pc] and aluminum(III) complex [(15C5)₄Pc]Al(OH). It was found that cation-induced formation of cofacial dimers [2I × 4MX] (M = K⁺, Rb⁺, X = CO₃^2-, OPic^-, OPiv^-, SO₄^2-, ClO₄^-, Br^-) resulted in significant enhancement of complex photostability.

A phthalonitrile precursor 4-(3-hydroxypropylmercapto)phthalonitrile (3) was synthesized via a base-catalyzed nucleophilic aromatic nitro displacement of 4-nitrophthalonitrile with the 3-mercapto-1-propanol. A novel tetrasubstituted metal-free phthalocyanine (4) (M = 2H) and its metal complexes (5–8) (M = Zn, Ni, Cu and Co) bearing 3-hydroxypropylmercapto moieties were prepared by the cyclotetramerization reaction of (3) with the appropriate materials. The visible spectra of the zinc(II) phthalocyanine (5) was recorded with different concentrations and different ions as Ag⁺, Hg²⁺ and Pb²⁺ in DMF and also with different solvents as dimethylformamide and pyridine. Fluorescence spectrum of the compound (5) was also studied. Temperature and frequency dependence of AC conductivity for (4–8) was investigated in air and under vacuum and were found to be ~10^-8–10^-5 S.m^-1. Thermal properties of the phthalocyanines were examined by differential scanning calorimetry. All the novel compounds have been characterized by elemental analysis, UV-vis, FT-IR, NMR and MS spectral data and DSC techniques.

Interaction of isomeric 4-nitro- or 3-nitrophthalonitrile with triethyl phosphonoacetate, diethyl cyanomethylphosphonate or tetraethyl methylenediphosphonate in basic conditions resulted in regioselective C-nucleophilic oxidative substitution of hydrogen ortho-located to nitro group, new phthalonitriles with diethoxyphosphorylmethyl or bis(diethoxyphosphoryl)methyl group were isolated in modest yields. In the same conditions one chlorine atom of tetrachlorophthalonitrile was regioselectively substituted with triethyl phosphonoacetate. In basic conditions, both parent phthalonitriles and corresponding zinc phthalocyanines with ortho-located nitro and diethoxyphosphoryl substituted methyl groups are involved in reversible acid-base interaction accompanied with large bathochromic shift of their long wavelength absorption maxima in visible or NIR region, correspondingly. Formation of tetraazachlorin- and tetraaza(iso)bacteriochlorin-like anions is proposed for explanation of this unprecedent bathochromic shift for phthalocyanines.

The design of a dendrimeric-like diglycerol-tetrasubstituted Zn(II) phthalocyanine resulted in a remarkably water-soluble compound due to the presence of 16 hydroxyls. Several parameters relevant to evaluate the photodynamic efficiency of a potentiel photosensitizer such as: aggregation behavior, fluorescence properties, singlet oxygen generation, binding to a carrier protein model (Bovine Serum Albumin) and partition coefficient have been measured. Biocompatibility was demonstrated by dark cytotoxicity in in vitro experiments. The absence of phototoxicity can be explained by an elevated hydrophilicity. All the collected data have confirmed that this new substitution pattern is promising to be used on phthalocyanines aiming at being photodynamic therapy agents.