Journal of Porphyrins and Phthalocyanines

We report herein that chiral and enantiopure compounds such nucleosides and peptides can pre-organize multi-porphyrinic systems and influence their properties. The first example given concerns star-shaped mutli-porphyrins with chiral and enantiopure nucleosidic linkers. If the configuration is indeed a star-shaped nanomolecule, it appears that the induced conformation is nothing as expected. The four peripheral Zn(II) porphyrins collapse over the free-base central one, inducing totally different photo-physical properties. Despite a minor expected light energy harvesting behavior, the principal capability of this system is to quench the collected light energy and convert it from radiative to non-radiative de-activation. The second example concerns polypeptides with pendant porphyrins. The peptidic backbone confers to the systems, after a certain degree of oligomerization, a 3${}_{\mathrm{\text{10}}}$ right handed helical conformation which induces cavities within the multi-porphyrinc architecture, ready to welcome guests and render, for example, the complexation of C${}_{\mathrm{\text{60}}}$ much easier. We thus have constructed novel organic photovoltaic systems using supramolecular complexes of porphyrin–peptide oligomers with fullerene clusters. The composite cluster OTE/SnO${}_{\mathrm{\text{2}}}$ electrode prepared with (P(ZnP)${}_{\mathrm{\text{16}}}+$ C${}_{\mathrm{\text{60}}}{)}_{\mathrm{\text{m}}}$, exhibits an impressive incident photon-to-photocurrent efficiency (IPCE) with values reaching as high as 56%. The power conversion efficiency of the (P(H${}_{\mathrm{\text{2}}}$P)${}_{\mathrm{\text{16}}}+$ C${}_{\mathrm{\text{60}}}{)}_{\mathrm{\text{m}}}$ modified electrode reaches 1.6%, which is 40 times higher than the value (0.043%) of the porphyrin monomer (P(H${}_{\mathrm{\text{2}}}$P)${}_{\mathrm{\text{1}}}$ $+$ C${}_{\mathrm{\text{60}}}{)}_{\mathrm{\text{m}}}$ modified electrode. Thus, the organization approach between porphyrins and fullerenes with polypeptide structures is promising, and may make it possible to further improve the light energy conversion properties by using a larger number of porphyrins in a polypeptide unit.

This contribution is focused on the supramolecular approach in exploration of aggregates formation by two different porphyrins wherein self-assembly plays an important role. Spectroscopic and microscopic studies usually provide information on investigations regarding the effects of various parameters on the fabrication of porphyrin aggregates by ionic self- assembly. Various properties of ionic self-assembled porphyrin nanorods have been investigated, including nonlinear optical (NLO) properties, and these studies were influenced by the fact that porphyrins have great thermal stability and extended $\pi$conjugated macro cyclic rings which give them large nonlinear optical effects. The major reasons limiting porphyrin nanorods photonic applications include the difficulty of handling them in liquid solutions and their degradation with long exposure to light. This necessitates the use of appropriate solid matrices to host the nanorods. Inspired by the precise organization and orientation of the chromophores in natural systems, attention has been on the design of nanometer sized chromophoric assemblies, which may find applications in the field of molecular photonics. However, it is challenging to design multicomponent systems with controlled structural arrangement at the molecular level. A lack of precise arrangement may have a negative impact on the construction of an efficient artificial light harvesting system. This review is focused on exploring the possibility of incorporating nanorods into polymer matrices to overcome the limiting factors of applications of these materials in photonic devices.

The first 5,10,15,20-tetra-(4-(triazol-1-yl)phenyl) porphyridine complex, [Zn${}_{\mathrm{\text{2}}}$Cl${}_{\mathrm{\text{4}}}$(5,10,15,20-tetra-(4-(triazol-1-yl)phenyl)porphyridine)]${}_{n}n$Cl•$n$H${}_{\mathrm{\text{3}}}$O•7$n$H${}_{\mathrm{\text{2}}}$O (1) has been synthesized via solvothermal reactions and characterized by single-crystal X-ray diffraction. Complex 1 is characteristic of a one-dimensional (1-D) structure, consisting of neutral [Zn${}_{\mathrm{\text{2}}}$Cl${}_{\mathrm{\text{4}}}$(5,10,15,20-tetra-(4-(triazol-1-yl)phenyl) porphyridine)]${}_n$ chains, isolated chloride ions and lattice water molecules. The zinc ion is in a four-coordinated tetrahedral geometry, and the porphyrin macrocycle is saddle-distorted. Photoluminescence measurement with solid-state samples discovers that it exhibits an emission in the green region of the light spectrum. Time-dependent density functional theory (TDDFT) calculation discovers that this emission can be attributed to the $\pi$–$\pi$* charge transfer. The cyclic voltammetry (CV) measurement reveals that it possesses an oxidation peak at 0.37 V.

A novel neodymium porphyrin [Nd(TPPS)]${}_n$•$n$H${}_{\mathrm{\text{3}}}$O (1) [H${}_{\mathrm{\text{6}}}$TPPS $=$ tetra(4-sulfonatophenyl)porphyrin] has been prepared through a solvothermal reaction and characterized by the X-ray single-crystal diffraction technique. Complex 1is crystallized in the $P$4/mcc space group of the tetragonal system. Complex 1 features a three-dimensional (3D) open framework with the pore size of the channels being of 6.9 $\AA$ × 8.2 $\AA$. A wide optical band gap of 4.98 eV is revealed by the solid-state UV/vis diffuse reflectance spectrum. The variable-temperature magnetic susceptibility obeys the Curie-Weiss law (${\chi }_m=c$/($T𝜃))$ with $C=$ 0.67 K and a negative Weiss constant $𝜃=$ -0.37 K as found by the magnetic measurements, suggesting the existence of an antiferromagnetic behavior. The N${}_{\mathrm{\text{2}}}$ adsorption and desorption curves show good reversibility and verify that the 3-D framework is flexible and can be compressed with the increasing pressure.

The synthesis and characterization of a hybrid Mn(III)-porphyrin magnetic nanocomposite is described. Moreover, a sustainable methodology for epoxidation of olefins is reported, using O${}_{\mathrm{\text{2}}}$ as a green oxidant and the magnetic nanoparticle as a recyclable catalyst. High activity in alkene oxidation was observed, with full selectivity for epoxide formation. The magnetic catalyst presented high stability, being recovered and reused in five consecutive runs without loss of catalytic activity or selectivity in cyclooctene oxidation. Moreover, the catalytic system showed very good reactivity toward epoxidation of a range of terminal, substituted, cyclic or acyclic, aliphatic and aromatic olefins, including terpene and steroid derivatives, affording a range of biologically relevant epoxides in excellent yields. The isobutyric acid, formed as side-product, was recovered with high yield and purity, which provides the potential reutilization of this important industrial product.

The self-aggregation process and its overcoming remain a barrier for the employment of many molecules as photosensitizers (PS) in photodynamic therapy (PDT). The B-ring isomer co-produced during the synthesis of the Verteporfin${}^{\mathrm{\text{®}}}$ (A-ring) is an example. Although both isomers possess similar in vitro/in vivo efficiency, the strong and not well-understood self-aggregation process of the B-ring derivative impairs its clinical use. This paper reports the use of theoretical calculus and its correlation with experimental analysis to find the main differences between the A and B-ring isomers. For that purpose, micelles of Pluronic${}^{\mathrm{\text{®}}}$ P-123 and Sodium Dodecyl Sulfate were chosen as simple membrane models and possible drug delivery system, as in the case of P-123. At physiological pH, the main reason for the high self-aggregation tendency is associated with the higher (22%) molecular volume of the B ring, which increases the van der Waals interactions. However, at mildly acidic conditions, the B ring possesses a shallow dihedral angle between the methyl ester group and the tetrapyrrolic macrocycle that favors the approach of units in the aggregate. These discrepancies directly affect the binding and stability of the isomers in the micelles. However, P-123 micelles were able to readily incorporate and monomerize/stabilize both PS over long periods. NOESY experiments confirmed a deep location of both PS inside P-123 micelles, which justifies their efficiency in preventing the self-aggregation process. These findings may substantiate new studies involving the marginalized B-ring isomers and encourage new development in formulations for their use in PDT.

We present the X-ray structures of the crystals of the ortho-, meta-, and para-F-tetraphenylporphyrins crystallized from different solvents to shed light on the differential solubility of these three isomers. The meta-F-TPP is 4300 times more soluble than the para-F-TPP isomer in chloroform. It is shown that the packing of the porphyrins in the crystal is not a key issue in this solubility difference. However, we discovered a large difference in the temperature factors of the phenyls and Fs in the various isomers and this gives us insight into the solubility differences.

A new series of mono-/di-aminated meso-tetraarylporphyrins has been synthesized and characterized by conventional spectroscopic methods. Crystal structure analysis shows that interactions involving halogens are the major contributors, and the relative contributions are 56% and 53% respectively for MB2c and MB3c. All the compounds were electrochemically analyzed under different reaction conditions and showed a positive shift in the reduction and oxidation potentials. The HOMO–LUMO energy gap was altered with respect to the nature of the supporting electrolyte and reference electrodes used. The linear behavior of Randles-Sevcik plots indicate that the redox processes are diffusion controlled; the first reduction/oxidation is a reversible one-electron step whereas the second reduction/oxidation is a quasi-reversible one-electron process. Results also reveal that the mono-aminated porphyrins are more electron deficient than non-aminated and di-aminated porphyrins.