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Antiviral medicines to treat COVID-19 are still scarce. Porphyrins and porphyrin derivatives (PDs) usually present broad-spectrum antiviral activity with low risk of resistance development. In fact, some PDs are clinically approved to be used in anti-cancer photodynamic therapy and repurposing clinically approved PDs might be an alternative to treat COVID-19. Here, we characterize the ability of temoporfin, verteporfin, talaporfin and redaporfin to inactivate SARS-CoV-2 infectious particles. PDs light-dependent and -independent effect on SARS-CoV-2 infectivity were evaluated. PDs photoactivation successfully inactivated SARS-CoV-2 with very low concentrations and light dose. However, only temoporfin and verteporfin inactivated SARS-CoV-2 in the dark, being verteporfin the most effective. PDs treatment reduced viral load in infected Caco-2 cells, while not inducing cytotoxicity. Furthermore, light-independent treatment with temoporfin and verteporfin act on early stages of viral infection. Using lipid vehicles as membrane models, we characterized PDs interaction to the viral envelope. Verteporfin presented the lowest IC50 for viral inactivation and the highest partition coefficients (K p ) towards lipid bilayers. Curiously, although temoporfin and redaporfin presented similar K p s, redaporfin did not present light-independent antiviral activity, and only temoporfin and verteporfin caused lipid membrane disorder. In fact, redaporfin is located closer to the bilayer surface, while temoporfin and verteporfin are located closer to the centre. Our results suggest that viral envelope affinity, with penetration and destabilization of the lipid bilayer, seems critical to mediate PDs antiviral activity. Altogether, these findings open new avenues for the off-label application of temoporfin and verteporfin in the systemic treatment of COVID-19., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Porphyrin photosensitizers are the classic drugs in clinical photodynamic therapy (PDT), but the hypoxia of tumor environment and the rapid oxygen consumption of PDT severely weaken their therapeutic effect. A recently reported water-dependent reversible photoacidity therapy (W-RPAT) is O 2 -independence, providing a solution for the treatment of hypoxic tumors. In this work, TPP-O-PEG5, a porphyrin derivative with binary properties of PDT and W-RPAT, is designed and synthesized for the first time. The nanoparticles (NPs) of TPP-O-PEG5 encapsulated with DSPE-mPEG2000, an amphiphilic polymer approved by Food and Drug Administration, can simultaneously produce reactive oxygen species and H + under irradiation of a 660 nm laser, and revert the H + back under darkness, presenting strong phototoxicity to multiple tumor cell lines with no obvious difference between the IC50 values tested under normoxic (≈20% O 2 ) and hypoxic (<0.5% O 2 ) conditions. Excitingly, in vivo experiments show that the therapeutic effect of TPP-O-PEG5 NPs on large hypoxic tumors is better than that of NPe6, a clinical porphin PDT drug. This work provides a novel strategy for porphyrin photosensitizers to break through the limitation of hypoxic environment, and significantly improve the phototherapeutic effect on hypoxic tumors., (© 2024 Wiley‐VCH GmbH.)

Porphyrin compounds are widely distributed in various natural products and biological systems. In this study, effects of porphyrin-related compounds including zinc protoporphyrin (ZnPP), protoporphyrin IX (PPIX), cyanocobalamin (CBL), hemin, and zinc phthalocyanine (ZnPC) were analyzed on color response of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) tetrazolium-based assay, a commonly-used method for analyzing cell viability. Color responses of MTT formazan formed in cells treated with ZnPP, PPIX, or ZnPC were significantly reduced even at submicromolar concentrations without affecting cell viability, whereas hemin and CBL did not. ZnPP, PPIX, and ZnPC rapidly induced degradation of MTT formazan already-produced by cells when exposed to light, but not under a dark condition. Photosensitizing properties of the three compounds were also verified through extensive generation of reactive oxygen species under light. The porphyrins did not affect the stability of water-soluble formazans including XTT, WST-1, WST-8, and MTS formazans. Several factors including different light sources and antioxidants modulated the degradation process of MTT formazan by the porphyrins. The results suggest that certain porphyrin compounds could cause a severe artifact in the MTT assay through rapid degradation of formazan dye due to their photosensitizing property, which needs to be considered carefully in the related assays.

Colloidal metallic nanoparticles have attracted a lot of interest in the last two decades owing to their simple synthesis and fascinating optical properties. In this manuscript, a study of the effect of both gold nanoparticles (Au NPs) and silver nanoparticles (Ag NPs) on the fluorescence emission (FE) of TPPS has been investigated utilizing steady-state fluorescence spectroscopy and UV-Vis spectrophotometry. From the observed electronic absorption spectra, there is no evidence of the ground state interaction between metallic Au NPs or Ag NPs with TPPS. On the other side, the FE spectra of TPPS have been quenched by both Ag and Au NPs. Via applying quenching calculations, Ag NPs showed only traditional static fluorescence quenching of TPPS with linear Stern-Volmer (SV) plots. On the contrary, quenching of TPPS emission by Au NPs shows composed models. One model is the sphere of action static quenching model that prevails at high quencher concentrations leading to non-linear SV plots with positive deviation. However, at low Au NPs concentrations, traditional dynamic quenching occurs with linear SV plots. The quantum calculations for TPPS structure have been obtained using Gaussian 09 software: in which the TPPS optimized molecular structure was achieved using DFT/B3LYP/6-311G (d) in a gaseous state. Also, the calculated electronic absorption spectra for the same molecule in water as a solvent are obtained using TD/M06/6-311G +  + (2d, 2p). Furthermore, the theoretical and experimental results comparable to UV-Vis spectra have been investigated., (© 2022. The Author(s).)

Persistent luminescence without excitation light and tissue autofluorescence interference holds great promise for biological applications, but is limited by available materials with long-wavelength emission and excellent clinical potential. Here, we report that porphyrin derivatives can emit near-infrared persistent luminescence over 60 min after cessation of excitation light or on interaction with peroxynitrite. A plausible mechanism of the successive oxidation of vinylene bonds was demonstrated. A supramolecular probe with a β-sheet structure was constructed to enhance the tumor targeting ability and the photoacoustic and persistent luminescence signals. Such probes featuring light-triggered function transformation from photoacoustic imaging to persistent luminescence imaging permit advanced image-guided cancer surgery. Furthermore, peroxynitrite-activated persistent luminescence of the supramolecular probe also enables rapid and precise screening of immunogenic cell death drugs., (© 2022 Wiley-VCH GmbH.)

Combinatorial photothermal and immunotherapy have demonstrated great potential to remove primary tumors, suppress metastases, and prevent tumor recurrence. However, this strategy still confronts patients with many limitations, such as complex components, sophisticated construction, and inadequate therapeutic efficacy. In this work, small molecules of porphyrin derivatives (PPor) which can self-assemble into monodispersed nanoparticles without supplement of any other ingredients or surfactants are developed. The formed PPor nanoparticles (PPor NPs) exhibit highly photothermal conversion efficiency of 70% and NIR-II luminous abilities originate from the strong intramolecular charge transfer (ICT) effect of D-A structure under 808 nm laser irradiation, thus achieving NIR-II fluorescence imaging guided photothermal therapy (PTT) against primary tumors with a high cure rate. More importantly, tumor-associated antigens (TAAs), together with damage-associated molecular patterns (DAMPs) released from PTT-treated cancer cells, are proved to elicit immune responses to some degree. After combination with programmed cell death-1 (PD-1) antibodies, a robust systematic antitumor immunity is generated to restrain both primary and abscopal tumors growth, prolong survival, and prevent pulmonary metastasis on an aggressive 4T1 murine breast tumor model. Thus, this study provides a promising therapeutic paradigm with porphyrin derivatives nano-assembly as phototheranostic agents for the treatment of aggressive tumors with high efficiency., (© 2022 Wiley-VCH GmbH.)

Pyrrole and porphyrin-derived nanoparticles have great potential use in bioimaging and therapy because of their unique magnetic, optical, and other photophysical properties, whereas the poor solubility in aqueous solution is one of the drawbacks of current photosensitizers for their photodynamic therapy (PDT) applications. Here, we developed a kind of water-soluble porphyrin-based nanoparticles that are coassembled mainly by the electrostatic interaction of anionic porphyrins and cationic tetraphenylmethane derivative. No aggregation-caused quenching (ACQ) was detected for these nanoparticles. In addition, the simple porphyrin transformation into nanoparticles improved their ability to generate reactive oxygen species singlet oxygen ( 1 O 2 ), which is an important factor causing apoptosis. The coassembled water-soluble porphyrin-based nanoparticles exhibited enhanced antitumor efficiency via PDT both in vitro and in vivo .

Meso-tetrakis(1,2-dimethylpyrazolium-4-yl)porphyrin sulfonate (TDMPzP), a water-soluble porphyrin derivative, was synthesized and used as a colorimetric reagent for Cu 2+ detection on a microfluidic paper-based analytical device (µPAD) using distance-based quantification. TDMPzP showed a high selectivity for Cu 2+ detection in aqueous solutions. When Cu 2+ was added to the TDMPzP under acidic conditions, a color change from green to a pink was observed by the naked eye. Under optimized conditions, the application of this system to a distance-based μPAD exhibited good analytical response. The presence of common metal ions (Al 3+ , Fe 3+ , Mg 2+ , Co 2+ , Mn 2+ , Zn 2+ , Pb 2+ , Cd 2+ , Sn 2+ , and Ni 2+ ) did not interfere with Cu 2+ detection within reasonable tolerance ratios. The lowest concentration of copper that could be measured was 1mgL -1 (1ppm) which meets the requirements for drinking water contamination regulations from the US Environmental Protection Agency (EPA) and World Health Organization (WHO) guidelines for drinking water. Real drinking water samples were analyzed to confirm the practical application of this system and the results showed good agreement with ICP-MS data. This distance-based µPAD based on TDMPzP for Cu 2+ detection is convenient and effective for real-time drinking water analysis., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Because it is highly infiltrative, malignant glioma is a cancer with a poor prognosis despite multidisciplinary treatment strategies, such as aggressive surgery and chemoradiotherapy, necessitating new therapeutic approaches to control migration of tumor cells. In our study, we investigated the efficacy of sonodynamic therapy of glioma cells in vitro using porphyrin derivatives, including 5-aminolevulinic acid, protoporphyrin IX and talaporfin sodium, as sonosensitizers. These substances have been known to accumulate in glioma cells and are expected to have cytotoxic effects on sonication. Our study found that the cytotoxicity of sonication of glioma cells is enhanced by each sonosensitizer and that the efficacy of sonodynamic therapy may depend on the degree of intracellular accumulation of sonosensitizer. Also, the study suggests that induction of apoptosis is a major mechanism underlying cell death. Though further investigations are necessary, our preliminary result indicates a potential for sonodynamic therapy with sonosensitizers in glioma treatment., (Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.)

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Persistent luminescence without excitation light and tissue autofluorescence interference holds great promise for biological applications, but is limited by available materials with long‐wavelength emission and excellent clinical potential. Here, we report that porphyrin derivatives can emit near‐infrared persistent luminescence over 60 min after cessation of excitation light or on interaction with peroxynitrite. A plausible mechanism of the successive oxidation of vinylene bonds was demonstrated. A supramolecular probe with a β‐sheet structure was constructed to enhance the tumor targeting ability and the photoacoustic and persistent luminescence signals. Such probes featuring light‐triggered function transformation from photoacoustic imaging to persistent luminescence imaging permit advanced image‐guided cancer surgery. Furthermore, peroxynitrite‐activated persistent luminescence of the supramolecular probe also enables rapid and precise screening of immunogenic cell death drugs. [ABSTRACT FROM AUTHOR]

A new π electron rich zinc complex was used as a fluorescent material in organic light-emitting diodes (OLEDs). Devices with a structure of indium tin oxide/poly (3,4-ethylenedi-oxythiophene):poly(styrenesulfonate) (PEDOT: PSS) (50 nm)/polyvinylcarbazole (60 nm)/Zn: %2 porphyrin derivatives (45 nm)/Al (150 nm) were fabricated. Porphyrin derivatives accounting for 2 wt.% in the π electron rich zinc complex were used as a host. The electroluminescence (EL) spectra of porphyrin derivatives indicated a red shift, as π electron rich zinc complex EL spectra. The device (4) has also a luminance of 3420 cd/m and maximum efficiency of 1.58 cd/A at 15 V, which are the highest values among four devices. The result of Commission International del'Eclairage (CIE) (X, Y) coordinate and EL spectrum of device (3) indicated that it is more red shifted compared to other devices. Results of this work indicate that π electron rich zinc complex is a promising host material for high efficiency red OLEDs and has a simple structure compared to Alq-based devices. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to test the action of Porphyrin compounds, Tetraphenylporphine sulfonate (TPPS), 5,10,15,20-Tetrakis (4-sulfonatophenyl) porphyrinato Iron(III) Chloride (FeTPPS) and 5,10,15,20-Tetrakis (4-sulfonatophenyl) porphyrinato Iron(III) nitrosyl Chloride (FeNOTPPS), on Na+, K+-ATPase of cell membrane of erythrocytes. Methods: Enzymatic assays, measuring the amount of inorganic phosphate produced, were used to estimate the activity of Na+, K+-ATPase. Results: The results show that Porphyrin compounds exert an insulin-like effect on Na+, K+-ATPase. They act by increasing the activity of the membrane-bound enzyme. Conclusion: All the three Porphyrin compounds increased the activity of erythrocyte Na+, K+-ATPase. The exact mechanism of action of these compounds is not clear. [ABSTRACT FROM AUTHOR]

To investigate photoelectric properties of meso-extended porphyrin derivatives with electron-donating or electron-withdrawing substituents, a series of functionalized porphyrin materials have been designed and synthesized by Suzuki coupling reaction. The meso-extended structures were fully characterized by 1H NMR, IR spectroscopy and mass spectrometry. The photophysical properties of porphyrin derivatives were carefully examined by UV-Visible and fluorescence spectra, and the solvatochromic effect was observed and discussed. In particular, Z-scan technique was employed to characterize the third-order nonlinear optical (NLO) properties of the products such as nonlinear absorption and refraction, the third-order nonlinear refractive indexes ( 픵(3)-value) of these porphyrin derivatives achieved 3.9×10−12 esu. In addition, the compounds could be self-assembled into highly organized morphologies through phase-exchange method. All the results indicated that the discotic materials have the potential for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Recently, third-order nonlinear properties of porphyrins and porphyrin polymers and coordination compounds have been extensively studied in relation to their use in photomedicine and molecular photonics. A new functionalized porphyrin dye containing electron-rich alkynes was synthesized and further modified by formal [2+2] click reactions with click reagents tetracyanoethylene (TCNE) and 7, 7, 8, 8-tetracyanoquinodimethane (TCNQ). The photophysical properties of these porphyrin dyes, as well as the click reaction, were studied by UV/Vis spectroscopy. In particular, third-order nonlinear optical properties of the dyes, which showed typical D-π-A structures, were characterized by Z-scan techniques. In addition, the self-assembly properties were investigated through the phase-exchange method, and highly organized morphologies were observed by scanning electron microscopy (SEM). The effects of the click post-functionalization on the properties of the porphyrins were studied, and these functionalized porphyrin dyes represent an interesting set of candidates for optoelectronic device components. [ABSTRACT FROM AUTHOR]

Dye sensitizers can significantly affect power conversion efficiency of dye-sensitized solar cells (DSSCs). Porphyrin-based dyes are promising sensitizers due to their performances in DSSCs. Here, based upon a N-fused carbazole-zinc porphyrin-free-base porphyrin triad containing an ethynyl-linkage (coded as DTBC), the novel porphyrin dyes named DTBC-MP and DTBC-TP were designed by varying the porphyrin-free-base units in the π conjugation of DTBC in order to study the effect of porphyrin-free-base in the modification of electronic structures and related properties. The calculated results indicate that, the extension of the conjugate bridge with the porphyrin-free-base unit results in elevation of the highest occupied molecular orbital (HOMO) energies, decrease of the lowest unoccupied molecular orbital (LUMO) energies, reduction of the HOMO-LUMO gap, red-shift of the absorption bands, and enhancement of the absorbance. The free energy changes demonstrate that introducing more porphyrin-free-base units in the conjugate bridge induces a faster rate of electron injection. The transition properties and molecular orbital characters suggest that the different transition properties might lead to a different electron injection mechanism. In terms of electronic structure, absorption spectra, light harvesting capability, and free energy changes, the designed DTBC-TP is a promising candidate dye sensitizer for DSSCs. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT and time-dependent-DFT (TD-DFT) were employed to investigate the vibroelectronic structural properties of porphyrin and some derivatives: unsubstituted porphyrin (TPyr), meso-tetraphenylporphyrin (TPP), mesotetrakis( p-sulfonatophenyl)porphyrin (TSPP), protonated-TPyr (H2TPyr), deuterated-H2TPyr (D4TPyr), protonated-TPP (H2TPP) and deuterated-H2TPP (D4TPP), protonated TSPP (H2TSPP), deuterated-H2TSPP (D4TSPP), dicationic TSPP (H6TSPP) and deuterated-H6TSPP (D8TSPP). The possible internal conversion (IC) and intersystem crossing (ISC) processes of these compounds were investigated. Finally, the relaxed ground state potential energy surface (PES) (S0), and singlet (Sn, n = 1-24) and triplet (Tn) excited state PESs of the TSPP molecule were calculated as function of the dihedral angle (Cα-Cm-Cϕ-C(ph)) rotation. The results of the calculations indicated that while the meso-substitutions caused a significant shift in frequencies when the meso-carbons within the parent-porphine (or TPyr) are involved in the vibrational motion of molecules; the protonation of the N atoms at the porphine/porphyrin core causes a significant blue shift when the H on the N atoms within the pyrroline are dominantly involved in the vibrational motions. The deuteration of N atoms not only caused a red-shift in the frequencies of the corresponding peaks below 1600 cm-1, but also produced new vibrational modes of frequencies in the 2565-2595 cm-1 range caused by the N-D bond stretching. Similarly, the deuteration of O atoms within the sulfonato groups (-SO3-) exhibited a new peak at around 2642 cm-1 due to O-D bond stretching. The measured Raman spectrum of the H2TSPP is assigned based on the predicted Raman spectra of the compounds studied here and measured Raman spectrum of the TPP (from our previous work). The IR spectrum is assigned based on our calculations and measured IR spectra obtained from the literature. The results of the TD-DFT calculations did not only indicate that the meso-substitution and protonation of the porphyrin bring about a significant read shift in the electronic transitions; but also provided a strong evidence for the IC from the Soret band to Q-bands beside possibility of the ISC process; its existence depend on the other excited state process such as much faster vibrational relaxation; the IC and etc. The ground state PES curve (S0) of the ionic TSPP exhibited two minima at the dihedral angle (Cα-Cm-Cϕ-C) of about 66° (corresponds to the lowest ground state) and 110° (corresponds to next energetically stable state or the local minima). The energy deference between these two minima is 0.0132 eV (or 106 cm-1) and the highest potential energy barrier when undergoing from the lowest ground state to this local state is only 0.0219 eV (177 cm-1; which is compatible with the thermal energy (kT) at 298 K is 207.2 cm-1. [ABSTRACT FROM AUTHOR]

In this work, in order to improve the low solubility and expand the applications of porphyrins in polysiloxanes, a series of designed siloxane-modified porphyrin derivatives was fabricated based on the Piers-Rubinsztajn reaction. The solubility of the porphyrin derivatives in polysiloxanes could be controlled by adjusting the siloxane chain length. Furthermore, the silicone-modified porphyrin derivatives were doped into a silicone elastomer prepolymer to obtain luminescent elastomers, which also showed good transparency and interfacial stability. In addition, the thermal stability and mechanical properties were well preserved compared with the original elastomer. Finally, based on the above-mentioned properties, an organosilicon elastomer doped with porphyrin showed good processability and plasticity, and could be fabricated into various complex three-dimensional models. The designed siloxane-modified porphyrin derivatives were fabricated using the Piers-Rubinsztajn reaction. Doping them into a silicone prepolymer produced homogeneous luminescent elastomers for the processing of 3D materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Two porphyrin derivatives with different substituents were investigated as dyes for the titanium dioxide (TiO) film electrode to construct new two-compartment photoelectrochemical biofuel cells (PEBFCs). The two porphyrin derivatives were tetrakis(4-carboxyphenyl)porphyrin (TCPP) and meso-tetra( p-hydroxyphenyl)porphine (THPP). To determine how cell performance was affected by the dye with different substituents, we analyzed the photochemical and photoelectrochemical properties of the two dyes by physical characterization and photoelectrochemical experiments. The UV-Vis absorption spectra and X-ray photoelectron spectra indicated that the interactions between the dye and TiO decreased in the order of TCPP > THPP, which was also in accord with the results of Fourier transform infrared. In addition, TCPP and THPP were calculated using the density functional theory and the time-dependent density functional theory, and the calculation result exhibited that the radiative lifetime decreased in the order of TCPP > THPP. Compared with THPP, TCPP with longer excited-state was expected to enhance the performance of a PEBFC. We measured and compared the incident photon-to-collected electron conversion efficiency and the light-to-electrical conversion efficiency (η) of the porphyrin-sensitized photoelectrochemical biofuel cell. The photovoltaic characteristics showed the TCPP was more effective compared to the THPP, which obviously showed that the experimental results were consistent with theoretical expectation. These results revealed that the kind of the substituent for the porphyrin influenced the photovoltaic properties of the PEBFC. [ABSTRACT FROM AUTHOR]

Highlights: [•] SWV were recorded for MPtz x Ph4−xPorph (x =0, 1, 2, 4; M=Ni2+, Cu2+, Pd2+). [•] Ptz and Porph contribute distinctly to the overall redox response. [•] Ptz and M2+ exert opposite effects on the redox activity of the Porph ring. [•] Structure–redox activity correlation obeys Hammett’s free energy relationship. [•] The spectral activity of the investigated compounds is decided by the Porph moiety. [Copyright &y& Elsevier]

The study of 27 new meso-substituted free-base and metal complexes of tetraphenylporphyrins with substitution by alkoxygroups (from -OC4H9 to -OC16H33) in para-, meta-, or ortho-position has been carried out. Out of 11 synthesized free-base alkoxysubstituted tetraphenylporphyrins - 4 possess mesomorphic state of columnar type and 1 - lyotropic mesomorphism in binary systems with toluene, benzene or chloroform. The important role of substituents position in phenyl rings of porphyrins was determined. It was established, that metal complexes (Cu, Ni, Zn, Ag, Pd, SnCl2, ZnOAc, VO) of mesogenic free-base porphyrins does not display liquid crystal properties. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to examine and determine binding affinities of the peripheral benzodiazepine receptor (PBR) with diamino acid derivatives of protoporphyrin IX with general structure PP(AA)2 in a function of environmental pH changes. Fluorescence intensity was used as a measure of protein association constant. Decrease in protein fluorescence, after titration with increasing concentration of porphyrins, gave evidence of interactions between PBR and examined ligands. Experimental data were fitted to theoretical curves, assuming different models of interactions. All examined ligands were best fitted to weak binding model. Increase in environmental acidity resulted in changes in association constants. For all examined derivatives association constants were at least twice higher in pH 5.5 as compared to pH 7.4 and 6.5. [Copyright &y& Elsevier]

Abstract: Conformations of two dodecameric porphyrin wheels adsorbed on a Cu(100) were probed by using scanning tunneling microscopy (STM). Whereas a wheel consisting of six meso–meso linked diporphyrins was detected as uniform ring structure, several different images with three discrete molecular heights were detected for a wheel consisting of six meso–meso, β-β,β-β triply-linked planar diporphyrins. These results indicate that the former has a conformation similar to that in a free space, while the latter has various conformations with respect to orientation of planar diporphyrin units toward the metal surface. Several discrete STM images of the latter have been interpreted in terms of possible eight conformations, which vary as to relative orientation of neighboring diporphyrin units. [Copyright &y& Elsevier]

Twenty four aminoporphyrin derivatives have been tested in vitro for their antibacterial photoactivity against Escherichia coli and Staphylococcus aureus. Two of these compounds, bearing polyamine units, exhibited a significant activity especially against Gram-negative bacteria (E. coli). [Copyright &y& Elsevier]

The need for new, chemically and physically stable luminescent materials operating with UV excitations has stimulated research on luminescence properties of doped sol–gel material. In this work we present technology of production of silica gels doped with organic molecules, lanthanide compounds and organic/inorganic composites. Optical properties of these materials as functions of temperature, concentration and excitation wavelength are presented. Dynamics of the excited states is discussed based on the decay times and emission efficiencies data. Mechanisms of ligand-to-metal energy transfer as well as other processes affecting emission efficiency are considered. Silica sol–gels doped with di-aminoacid derivatives of porphyrins: PP(Ser)2(Arg)2, PP(Ala)2(Arg)2, PP(Met)2(Arg)2, where Met, Arg and Ser denote methionine, serine and arginine aminoacids, respectively, and H2TTMePP {tetrakis[4-(trimethylammonio)phenyl]-21H,23H-porphine} have been obtained and spectroscopically studied. The samples emit only from the lowest excited singlet state (S1). Intensity of this emission depends on the concentration of the active molecule and time of the exposition to the excitation beam. The sample containing PP(Ser)2 (Arg)2 co-doped with Tb(III) ions exhibits only 5D4 emission from the metal center. When co-doped with Pr(III) ions it displays only the S1 emission and it has been shown that the metal ions affect the S2 → S1 internal conversion. These materials can find applications as phosphors or sensors of UV irradiation. The efforts have been undertaken also to obtain chiral anisotropic materials. [Copyright &y& Elsevier]

Using density functional theory and ZINDO-SOS method, the two-photon absorption properties of a series of porphyrin derivatives have been theoretically investigated. The calculated results are in good agreement with the experimental observations. It is found that the central porphyrin moiety has the electron-donating ability, which is favor of the charge transfer from the center to the electron acceptor ends. As a consequence, the compound [5,15-bis[(4′-nitrophenyl)ethynyl]-10,20-diphenylporphinato]zinc(II) presents the largest two-photon absorption cross-section—3279×10-50cm4 s/photon, which is more than 100 times as that for (porphinato)-zinc (II). This type of symmetrically substituted porphyrin derivatives will be a promising direction for further development of novel TPA dyes. [Copyright &y& Elsevier]

The photochemical and photoelectrochemical properties of two porphyrin derivatives with different numbers of carboxyl groups were investigated. The two porphyrin derivatives are 5-(4-carboxyphenyl)-10,15,20-tritolylporphyrin (H2TC1PP) and 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (H2TC4PP). The interaction between the porphyrin and TiO2 is determined by the UV–vis spectra. Differences in adsorption behavior of the two porphyrin derivatives on the TiO2 electrode surface were observed. The IR data suggest that both of the porphyrins adsorb by bridging or bidentate chelate coordination on the TiO2 surface. Comparing the luminescence spectra of the two porphyrins in solution and the solid state, no spectral difference was observed. However, we found that the variation in the number of carboxyl groups has an influence on the fluorescence spectra of the adsorbed TiO2 electrode. Furthermore, we measured and compared the incident photon-to-current conversion efficiency (IPCE) and the light-to-electrical conversion efficiency of the porphyrin-sensitized solar cell. These results revealed that the number of functional groups influenced the photoelectrochemical properties of the cell. [Copyright &y& Elsevier]

A series of porphyrin derivatives containing carboxylic-, sulfo- and hydro- groups, 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP), 5,10,15,20-tetrakis(4-sulfophenyl)porphyrin (TSPP) and 5,10,15,20-tetraphenyl-porphyrin (TPP), were examined as sensitizers for porous nanocrystalline TiO2. The difference in the adsorption behavior on the TiO2 electrode surface was discussed. The interaction between the porphyrins and the TiO2 surface was determined and compared using UV–Vis spectra and X-ray photoelectron spectroscopy (XPS). The luminescence spectra of the porphyrins in DMF solution and adsorbed onto TiO2 electrodes were measured. The ionization potentials of the porphyrins in the solid state and adsorbed onto TiO2 electrodes were determined by a new approach using an apparatus for measuring the emission yield under atmospheric conditions. The importance of the binding states between the dye and TiO2 surface was discussed by comparison of the energy conversion efficiency in a dye-sensitized solar cell. The results indicate that the binding state and the amount of adsorbed dye are important factors affecting the properties of the dye-sensitized solar cell. [Copyright &y& Elsevier]

The mitochondrial 2-oxoglutarate carrier (OGC), isolated and purified from rat brain mitochondria, was reconstituted into proteoliposomes to study the interaction with hemin, a porphyrin derivative, which may result from the breakdown of heme-containing proteins and plays a key role in several metabolic pathways. By kinetic approaches, on the basis of the single binding centre gated pore mechanism, we analyzed the effect of hemin on the transport rate of OGC in uptake and efflux experiments in proteoliposomes reconstituted in the presence of the substrate 2-oxoglutarate. Overall, our experimental data fit the hypothesis that hemin operates a competitive inhibition in the 0.5–10 µM concentration range. As a consequence of the OGC inhibition, the malate/aspartate shuttle might be impaired, causing an alteration of mitochondrial function. Hence, considering that the metabolism of porphyrins implies both cytoplasmic and mitochondrial processes, OGC may participate in the regulation of porphyrin derivatives availability and the related metabolic pathways that depend on them (such as oxidative phosphorylation and apoptosis). For the sake of clarity, a simplified model based on induced-fit molecular docking supported the in vitro transport assays findings that hemin was as good as 2-oxoglutarate to bind the carrier by engaging specific ionic hydrogen bond interactions with a number of key residues known for participating in the similarly located mitochondrial carrier substrate binding site. [ABSTRACT FROM AUTHOR]

Meso-(2-thienyl) porphyrin derivatives were synthesized. Excited state reverse saturable absorption was observed at 532 nm while two-photon absorption was observed at 800 nm. The nonlinear optical properties are increased by introducing the donator of thienyl group. Meso-(2-thienyl) porphyrin derivatives showed good nonlinear response at low energy. High third-order nonlinear optical susceptibility values (10−10 esu) of metal-free porphyrin derivatives were obtained. The mechanisms of third-order nonlinearity were proposed by the pump-probe experiment. With the observed fast electronic nonlinearities the studied molecules are potential candidates for use as optical limiters or optical switches. • Three new meso-(2-thienyl)porphyrin derivatives were synthesized. • These metal-free porphyrin derivatives demonstrated high third-order nonlinear optical susceptibility values of 10−10 esu. • Meso-tetrakis (2-thienyl) porphyrin reached the two-photon absorption cross section of 4076 GM. • The mechanisms of third-order nonlinearity were proposed by the pump-probe experiment. [ABSTRACT FROM AUTHOR]

Porphyrin ( Pr), porphycene ( Pc), and [22]porphyrin(2.2.2.2) ( P[22]) have been theoretically investigated. We design 2 highly conjugated macrocycles containing 4 pyrroles with different linkage bridges, which are named for 4 pyrrole ( Pf) and methylene-dipyrrolidine ( Pm), as the theoretical model so as to investigate the stability, aromaticity, and photophysical behavior of these porphyrin derivatives, and the influence of getting or losing electron to the neutral molecule. The geometric structures of the molecules are optimized by density functional theory method. The absorptions are calculated by the time-dependent density functional theory method. Based on the optimized structures, the nucleus-independent chemical shifts (NICS) are calculated. The molecule with negative NICS value possesses larger highest occupied molecular orbital (HOMO)-lowest occupied molecular orbital (LUMO) gap than that with positive NICS value, the molecule with bigger positive NICS value possesses smaller HOMO-LUMO gap, and the molecule with bigger negative NICS value (in absolute value) possesses bigger HOMO-LUMO gap. The current density indicates that the π-electron delocalization is more effective in Pr and Pc than in Pf, Pm, and P[22] and corresponds to the stability of molecules. The absorptions of the molecules are all in the UV-visible and infrared regions. The major transitions for most of the molecules are all from HOMO to LUMO. Compared with Pf 2−, Pr 2−, Pc 2−, and P[22] 2−, Pm 2− shows distinctive photophysical properties, which is due to the reduced HOMO-LUMO gap, structural distortion, and strong antiaromaticity. [ABSTRACT FROM AUTHOR]

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β,β-Tripyrrin-bridged 'earring' porphyrins are synthesized by Suzuki-Miyaura cross coupling reactions. [ABSTRACT FROM AUTHOR]

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