Journal of Porphyrins and Phthalocyanines

The mechanism of photoconductivity in a crystalline photoconductor synthesized from 1:1 ratio of meso-tetra(4-pyridyl)porphyrin (TPyP) and meso-tetra(4-sulfonatophenyl)porphyrin (TSPP) ionic tectons was examined. The rod-like crystals of TPyP:TSPP insulate in the dark but become photoconducting on illumination and a portion of the photoinduced current persists after the laser light is turned off. This persistent photoconductivity (PPC) is investigated as a function of laser illumination wavelength, laser power, and sample temperature. The primary charge carriers in the TPyP:TSPP upon photoexcitation are electrons and the charge recombination mechanism follows monomolecular kinetics. The number of electrons contributing to the photocurrent is directly proportional to the number of photons absorbed thus, the mechanisms of the photoconductivity resulting from excitations within the Soret band and the Q-band are the same. The PPC is interpreted to be the result of the formation of photoinduced metastable defects that allow for Miller–Abrahams-like hopping conductivity. The TPyP:TSPP has an incommensurately modulated crystal lattice and its proposed model structure is based on both ionic and neutral porphyrin tectons. The thermogravimetric analysis shows that the porphyrin crystals undergo dehydration on heating (˜50 ^∘C) by losing water molecules located in the crystalline channels. Temperature dependent XRD indicates that dehydration causes irreversible changes to the crystal structure. The loss of crystallinity observed with heating the TPyP:TSPP crystals above 90 ^∘C causes approximately 25% loss in photoconductivity but has little effect on the lifetime associated with the persistent photoconductivity.

The present work describes the use of a magnetic porphyin (5-(4-carboxy-phenyl)-10,15,20-triphenyl-21H, 23H-porphyrin TPP) nanoconjugate (SPION-TPP) for destroying pathogenic bacteria followed by the recovery of the magnetic photosensitizer. SPION-TPP was tested for its activity against two different gram-positive bacterial strains (Staphylococcus aureus and Steptoccoccus mutans). It is observed that SPION-TPP at a very low concentration of 0.5 $\mu$M is effective in destroying gram-positive bacteria (10${}^{\mathrm{\text{7}}}$–10${}^{\mathrm{\text{8}}}$ CFU ml${}^{\mathrm{\text{-1}}})$ S. aureus with several orders reduction and few orders in S. mutans. The aim of this work is to combine photoactivity against microorganisms imparted by the photosensitizer with the possibility of recovering the nanoconstruct with magnets for disposal/reuse.

Photodynamic therapy (PDT) has been a potential therapeutic method for the treatment of various cancers, with photosensitizer being the key component in photodynamic therapy. In this paper, we prepared a photosensitizer 3-(1-hydroxylethyl)-3-devinyl-13¹-(dicyanomethylene) pyropheophorbide-a methyl ester (HDCPPa), based on chlorophyll pyropheophorbide-a according to the previous report, and systematically investigated the fluorescence emission spectrum and ultraviolet absorption spectrum HDCPPa has long absorption in the near-infrared spectral region (around 695 nm). The excitation wavelength and the emission wavelength were 415 nm and 699 nm respectively in dichloromethane, ¹O₂ quantum yield was 63.5%. HDCPPa also had high stability in PBS solution, DMEM cell culture medium and normal saline (NS) in vitro. After irradiation by the light of 675 nm (10 J.cm${}^{-2}$) for 70 min the degradation rate of HDCPPa was 12.5%, which indicated that the target compound showed high stability under light. The in vitrophotodynamic therapy activities against HeLa cells were also studied, which showed that HDCPPa had extremely low dark toxicity but great phototoxicity, and the cell viability is lower than 10% under the light irradiation of 675 nm (10 J.cm${}^{-2}$). Moreover, HDCPPa can quickly enter the cell after being incubated with HeLa cells in less than 30 min. We also evaluated the mechanism of the photochemical reaction, which had proved that Type II is primarily responsible for the cell death. Therefore HDCPPa could serve as a very promising photosensitizer for photodynamic therapy.

Novel octa-phenotiazine, octa-benzoazepine and octa-carbazole substituted magnesium(II) (MgPz-I-III) and zinc(II) (ZnPz-I-III) porphyrazines were synthesized from 2,3-bis[6-(4a,10a-dihydro-phenothiazin-10-yl)-hexylsulfanyl]-but-2-enedinitrile (5), 2,3-bis [6-(4a,11a-dihydro-dibenzo[b,f]azepin-5-yl)-hexysulfan-yl]-but-2-enedinitrile (8) and 2,3-bis(6-carbazol-9-yl-hexylsulfanyl)-but-2-enedinitrile (10), respectively. These dinitrile derivatives 5, 8 and 10 were also prepared by the reaction of 1,2-dicyano-1,2-ethylenedithiolate di-sodium salt (4) with 10-(6-bromohexyl)-10H-phenothiazine (3), 5-(6-bromohexyl)-5H-diben-zo[b,f]azepine (7) and 9-(6-bromo-hexyl)-9H-carbazole (9), respectively. Porphyrazino-zinc(II) complexes were synthesized by one-step reaction using Zn(BuO)${}_{\mathrm{\text{2}}}$ as a template agent. All the novel compounds were characterized by elemental analysis and different spectroscopic methods such as ${}^{\mathrm{\text{1}}}$H NMR, ${}^{\mathrm{\text{13}}}$C NMR, FT-IR, UV-Vis and mass. The photochemical properties including photodegradation and singlet oxygen generation for magnesium(II) and zinc (II) porphyrazine complexes were studied in dimethylsulfoxide solutions for determination of their photosensitizer behaviors.

The synthesis, acid-base properties, and kinetics of Cu${}^{2+}$ incorporation into water-soluble highly substituted porphyrins were studied. The basicity increased and the stepwise acid-base equilibrium was clarified by increasing the number of phenyl groups at the $\beta$ position, and the basicity of a dodeca-substituted porphyrin increased with the ionic strength. The metalation reaction of the dodeca-substituted porphyrin with Cu${}^{2+}$ in aqueous solution revealed a biphasic absorbance change at 453 nm. Plots of $k_{\mathrm{\text{pre}}}$ or$k_{\mathrm{\text{post}}}$ vs. the Cu${}^{2+}$ concentration and of log ($k_{\mathrm{\text{pre}}}$ or$k_{\mathrm{\text{post}}}$/$k_I=$ 0) vs. the ionic strength show that $k_{\mathrm{\text{pre}}}$ is dependent on the Cu${}^{2+}$ concentration and ionic strength, while $k_{\mathrm{\text{post}}}$ is independent of these parameters. These results confirm the stepwise metalation mechanism and the existence of an intermediate in aqueous solution, which is indicated by the biphasic absorbance change at 453 nm.

Two series of meso-phenyl fluorinated porphyrins and their metal complexes, 5,10,15,20-tetrakis(2$\prime$,4$\prime$,6$\prime$-trifluorophenyl)porphyrin, MT(2$\prime$,4$\prime$,6$\prime$-TFP)Ps (2a–2d) and 5,10,15,20-tetrakis[3$\prime$,5$\prime$-bis(trifluoromethylphenyl)]porphyrin, MT(3$\prime$,5$\prime$-BTFMP)Ps (3a–3d); where M $=$ 2H; Ni(II); Cu(II) and Zn(II) have been synthesized and characterized using various spectroscopic techniques including UV-visible, fluorescence and ${}^{\mathrm{\text{1}}}$H NMR and mass spectrometry. Electronic absorption spectra of porphyrins show the typical Soret (B) and visible (Q) bands. Free ligands and zinc(II) derivatives display two well-defined emission bands around 600–660 nm and 650–720 nm upon exciting the Soret band. Porphyrins, 1d, 2a, 2b, 2c, 3a and 3d were structurally characterized by single crystal XRD analysis, and various intermolecular interactions present in them were quantified on the basis of Hirshfeld surfaces and 2D fingerprint plots. Electrochemical studies were performed and the HOMO–LUMO energy gap is high for all the porphyrins compared to MTPPs.