Vibration and Fluorescence Spectra of Porphyrin-Cored 2,2-Bis(methylol)-propionic Acid Dendrimers

Insights into the phototautomerism of free-base 5, 10, 15, 20-tetrakis(4-sulfonatophenyl) porphyrin

Phototautomerism in the excited states of free-base 5, 10, 15, 20-tetrakis(4-sulfonatophenyl) porphyrin (H₂TPPS^4-) has been investigated combining, for the first time, advanced Electron Paramagnetic Resonance (EPR) with fluorescence and Raman spectroscopy. Triplet EPR spectroscopy, performed in protic and deuterated solvents and in the presence of photoselection, confirms the occurrence of phototautomerization and additionally suggests the formation of the cis tautomer as a minor component. The zero-field splitting parameters and triplet sublevel populations indicate that the process is slow in the triplet state. The results obtained by EPR combined with photoselection and fluorescence anisotropy have been interpreted within a model which accounts for a fast trans-trans tautomerization promoted by a spin-vibronic coupling mechanism for intersystem crossing, with an even distribution of the two trans tautomers at liquid nitrogen temperatures for H₂TPPS^4-.

Self-Assembly of Chiro-Optical Materials from Nonchiral Oligothiophene-Porphyrin Derivatives and Random Coil Synthetic Peptides

Biomimetic chiral optoelectronic materials can be utilized in electronic devices, biosensors and artificial enzymes. Herein, this work reports the chiro-optical properties and architectural arrangement of optoelectronic materials generated from self-assembly of initially nonchiral oligothiophene-porphyrin derivatives and random coil synthetic peptides. The photo-physical- and structural properties of the materials were assessed by absorption-, fluorescence- and circular dichroism spectroscopy, as well as dynamic light scattering, scanning electron microscopy and theoretical calculations. The materials display a three-dimensional ordered helical structure and optical activity that are observed due to an induced chirality of the optoelectronic element upon interaction with the peptide. Both these properties are influenced by the chemical composition of the oligothiophene-porphyrin derivative, as well as the peptide sequence. We foresee that our findings will aid in developing self-assembled optoelectronic materials with dynamic architectonical accuracies, as well as offer the possibility to generate the next generation of materials for a variety of bioelectronic applications.

Computational investigation on the geometry and electronic structures and absorption spectra of metal-porphyrin-oligo- phenyleneethynylenes-[60] fullerene triads

In this work, we focus our attention on the influence of 2nd-row transition metals on the structural geometries, electronic structures, and absorption characteristics of porphyrin linked with the C₆₀ fullerene with oligo-p-phenyleneethynylenes (MP-C₆₀-oligo-PPEs) compounds. The DFT/B3PW91-D3 and CAM-B3LYP-D3/6-31G (d) calculations revealed that various metals embedded within the porphyrin moiety give different bridge conformations and different HOMO-LUMO energy levels. We calculate the UV-Vis spectra and absorption parameters using the time-dependent ZINDO/S approach. Our findings indicate that all the compounds have enhanced absorptions in the visible light range, and their molecular orbital energies adopt the condition of sensitizers. However, all of the complexes except down spin states exhibit considerably charge spatial separation. The results suggest that the ZnP-C₆₀-oligo-PPEs triad can meet the necessary conditions of the sensitizer of dye-sensitized solar cells (DSSCs) in comparison with other counterparts and could be an optimum triad compound for potential application in photovoltaic devices.

Amphiphilic Protoporphyrin IX Derivatives as New Photosensitizing Agents for the Improvement of Photodynamic Therapy

Photodynamic therapy (PDT) is a non-invasive therapeutic modality based on the interaction between a photosensitive molecule called photosensitizer (PS) and visible light irradiation in the presence of oxygen molecule. Protoporphyrin IX (PpIX), an efficient and widely used PS, is hampered in clinical PDT by its poor water-solubility and tendency to self-aggregate. These features are strongly related to the PS hydrophilic–lipophilic balance. In order to improve the chemical properties of PpIX, a series of amphiphilic PpIX derivatives endowed with PEG₅₅₀ headgroups and hydrogenated or fluorinated tails was synthetized. Hydrophilic–lipophilic balance (HLB) and log p-values were computed for all of the prepared compounds. Their photochemical properties (spectroscopic characterization, photobleaching, and singlet oxygen quantum yield) were also evaluated followed by the in vitro studies of their cellular uptake, subcellular localization, and photocytotoxicity on three tumor cell lines (4T1, scc-U8, and WiDr cell lines). The results confirm the therapeutic potency of these new PpIX derivatives. Indeed, while all of the derivatives were perfectly water soluble, some of them exhibited an improved photodynamic effect compared to the parent PpIX.

Porphyrin-decorated ZnO nanowires as nanoscopic injectors for phototheragnosis of cancer cells

Newly synthesized protoporphyrin-decorated ZnO-nanowires exhibited optical waveguided and photodynamic properties to be useful nanoscopic injectors for photo-theragnosis of cancer cells.

Sulphonic acid functionalized porphyrin anchored with a meso-substituted triazolium ionic liquid moiety: a heterogeneous photo-catalyst for metal/base free C–C cross-coupling and C–N/C–H activation using aryl chloride under visible light irradiation

We report an easy process to synthesize sulphonic acid functionalized porphyrin with meso-substituted triazolium ionic liquid moiety for metal/base free C–C cross-coupling and C–N/C–H activation using aryl chloride under visible light irradiation.

Synthesis and physico-chemical properties of a H-cardanol triazole zinc porphyrin conjugate

Although a large number of natural and non-natural metalloporphyrins are known, examples with fluorescence and fat-soluble properties are rare. We have achieved the synthesis of a fluorescent and fat-soluble zinc porphyrin incorporating four units of hydrogenated cardanol (H-cardanol). The synthesis is sustainable since the product is derived from cashew-nut shell liquid (CNSL), which is a renewable and bio-waste material. The H-cardanol triazole zinc porphyrin conjugate (HTZPC) was synthesized through applying a copper(i) catalyzed azide–alkyne cycloaddition (CuAAC) reaction between a H-cardanol derived azide and a tetraarylporphyrin derived alkyne. The absorption and emission properties of the hydrocarbon solvent soluble HTZPC were evaluated using UV-vis and fluorescence emission spectra obtained in various solvents. The results were compared with related molecules like a triazole-zinc porphyrin conjugate (TZPC), zinc tetra-C(4)-methoxyphenyl porphyrin (ZP), and a H-cardanol-triazole conjugate (HTC). The results showed that HTZPC undergoes J-type aggregation in both non-polar and highly polar solvents, which is dictated by van der Waals attractive forces between H-cardanol units in polar solvents (e.g. methanol and dimethylformamide) and π–π stacking interactions between porphyrin units in non-polar solvents (hexane). Moreover, the spectra indicated that the triazole units could stabilize the zinc porphyrin via intermolecular coordinate-complex formation. We anticipate that fat-soluble HTZPC could find applications in medical fields (e.g. in the photodynamic therapy of fat tissue).

A fluorescent and fat-soluble zinc porphyrin incorporating four units of hydrogenated cardanol (H-cardanol) was synthesized, and its physico-chemical properties were characterized.

Synthesis and Characterization of Novel Fluoro-glycosylated Porphyrins that can be Utilized as Theranostic Agents

Small molecules with modalities for a variety of imaging techniques as well as therapeutic activity are essential, as such molecules render opportunities to simultaneously conduct diagnosis and targeted therapy, so called theranostics. In this regard, glycoporphyrins have proven useful as theranostic agents towards cancer, as well as noncancerous conditions. Herein, the synthesis and characterization of heterobifunctional glycoconjugated porphyrins with two different sugar moieties, a common monosaccharide at three sites, and a 2-fluoro-2-deoxy glucose (FDG) moiety at the fourth site are presented. The fluoro-glycoconjugated porphyrins exhibit properties for multimodal imaging and photodynamic therapy, as well as specificity towards cancer cells. We foresee that our findings might aid in the chemical design of heterobifunctional glycoconjugated porphyrins that could be utilized as theranostic agents.

Multiporous Supramolecular Microspheres for Artificial Photosynthesis

Artificial photosynthesis shows a promising potential for sustainable supply of nutritional ingredients. While most studies focus on the assembly of the light-sensitive chromophores to 1-D architectures in an artificial photosynthesis system, other supramolecular morphologies, especially bioinspired ones, which may have more efficient light-harvesting properties, have been far less studied. Here, MCpP-FF, a bioinspired building block fabricated by conjugating porphyrin and diphenylalanine, was designed to self-assemble into nanofibers-based multiporous microspheres. The highly organized aromatic moieties result in extensive excitation red-shifts and notable electron transfer, thus leading to a remarkable attenuated fluorescence decay and broad-spectrum light sensitivity of the microspheres. Moreover, the enhanced photoelectron production and transfer capability of the microspheres are demonstrated, making them ideal candidates for sunlight-sensitive antennas in artificial photosynthesis. These properties induce a high turnover frequency of NADH, which can be used to produce bioproducts in biocatalytic reactions. In addition, the direct electron transfer makes external mediators unnecessary, and the insolubility of the microspheres in water allows their easy retrieval for sustainable applications. Our findings demonstrate an alternative to design new platforms for artificial photosynthesis, as well as a new type of bioinspired, supramolecular multiporous materials.

Photochemical internalization of bleomycin and temozolomide--in vitro studies on the glioma cell line F98

Here we evaluate the photosensitizer meso-tetraphenyl chlorin disulphonate (TPCS2a) in survival studies of rat glioma cancer cells in combination with the novel photochemical internalization (PCI) technique. The tested anticancer drugs were bleomycin (BLM) and temozolomide (TMZ). Glioma cells were incubated with TPCS2a (0.2 μg ml(-1), 18 h, 37 °C) before BLM or TMZ stimulation (4 h) prior to red light illumination (652 nm, 50 mW cm(-2)). The cell survival after BLM (0.5 μm)-PCI (40 s light) quantified using the MTT assay was reduced to about 25% after 24 h relative to controls, and to 31% after TMZ-PCI. The supplementing quantification by clonogenic assays, using BLM (0.1 μm), indicated a long-term cytotoxic effect: the surviving fraction of clonogenic cells was reduced to 5% after light exposure (80 s) with PCI, compared to 70% in the case of PDT. In parallel, structural and morphological changes within the cells upon light treatment were examined using fluorescence microscopy techniques. The present study demonstrates that PCI of BLM is an effective method for killing F98 glioma cells, but smaller effects were observed using TMZ following the "light after" strategy. The results are the basis for further in vivo studies on our rat glioma cancer model using PDT and PCI.

Ruthenium porphyrin-induced photodamage in bladder cancer cells

Photodynamic therapy (PDT) is a noninvasive treatment for solid malignant and flat tumors. Light activated sensitizers catalyze photochemical reactions that produce reactive oxygen species which can cause cancer cell death. In this work we investigated the photophysical properties of the photosensitizer ruthenium(II) porphyrin (RuP), along with its PDT efficiency onto rat bladder cancer cells (AY27). Optical spectroscopy verified that RuP is capable to activate singlet oxygen via blue and red absorption bands and inter system crossing (ISC) to the triplet state. In vitro experiments on AY27 indicated increased photo-toxicity of RuP (20μM, 18h incubation) after cell illumination (at 435nm), as a function of blue light exposure. Cell survival fraction was significantly reduced to 14% after illumination of 20μM RuP with 15.6J/cm(2), whereas the "dark toxicity" of 20μM RuP was 17%. Structural and morphological changes of cells were observed, due to RuP accumulation, as well as light-dependent cell death was recorded by confocal microscopy. Flow cytometry verified that PDT-RuP (50μM) triggered significant photo-induced cellular destruction with a photoxicity of (93%±0.9%). Interestingly, the present investigation of RuP-PDT showed that the dominating mode of cell death is necrosis. RuP "dark toxicity" compared to the conventional chemotherapeutic drug cisplatin was higher, both evaluated by the MTT assay (24h). In conclusion, the present investigation shows that RuP with or without photoactivation induces cell death of bladder cancer cells.

Synthesis of meso-(4′-cyanophenyl) porphyrins: efficient photocytotoxicity against A549 cancer cells and their DNA interactions

A facile I(iii)-mediated synthesis of cyanoporphyrins and their significant photocytotoxicity (IC₅₀ = 54 nM) against A549 cancer cell line has been described.

Fluorescence and FTIR Spectra Analysis of Trans-A₂B₂-Substituted Di- and Tetra-Phenyl Porphyrins

A series of asymmetrically substituted free-base di- and tetra-phenylporphyrins and the associated Zn-phenylporphyrins were synthesized and studied by X-ray diffraction, NMR, infrared, electronic absorption spectra, as well as fluorescence emission spectroscopy, along with theoretical simulations of the electronic and vibration structures. The synthesis selectively afforded trans-A₂B₂ porphyrins, without scrambling observed, where the AA and BB were taken as donor- and acceptor-substituted phenyl groups. The combined results point to similar properties to symmetrically substituted porphyrins reported in the literature. The differences in FTIR and fluorescence were analyzed by means of detailed density functional theory (DFT) calculations. The X-ray diffraction analysis for single crystals of zinc-containing porphyrins revealed small deviations from planarity for the porphyrin core in perfect agreement with the DFT optimized structures. All calculated vibrational modes (2162 modes for all six compounds studied) were found and fully characterized and assigned to the observed FTIR spectra. The most intense IR bands are discussed in connection with the generic similarity and differences of calculated normal modes. Absorption spectra of all compounds in the UV and visible regions show the typical ethio type feature of meso-tetraarylporphyrins with a very intense Soret band and weak Q bands of decreasing intensity. In diphenyl derivatives, the presence of only two phenyl rings causes a pronounced hypsochromic shift of all bands in the absorption spectra. Time-dependent DFT calculations revealed some peculiarities in the electronic excited states structure and connected them with vibronic bands in the absorption and fluorescence spectra from associated vibrational sublevels.

Structural parameters and vibrational spectra of a series of zinc meso-phenylporphyrins: a DFT and experimental study

The influences of meso-phenyl substitution on the geometric structure and vibrational spectra have been studied by DFT calculation (B3LYP/6-31G(d)) and experiment on a series of zinc porphyrins (ZnTPP: zinc 5,10,15,20-tetraphenylporphyrin; ZnTrPP: zinc 5,10,15-triphenylporphryin; ZnDPP: zinc 5,15-dipenylporphyirn; ZnMPP: zinc 5-monophenylporphyrin; ZnP: zinc porphine). Calculation indicates that meso-phenyl substitution gives rise to slight out-of-plane distortion but significant in-plane distortion, especially for the configuration around C(m) atom, to zinc porphyrin. The assignment of experimental vibrational spectra was proposed mainly on the basis of calculation. Different shifting tendency upon meso-phenyl substitution is observed for different structure-sensitive bands, such as the shifting of nu(2), nu(3), nu(6), and nu(8) modes toward higher frequencies and nu(4) and nu(28) modes toward lower frequencies, upon meso-phenyl substitution. This is attributed primarily to in-plane nuclear reorganization effect (IPNR), though the contribution from out-of-plane distortion cannot be excluded completely. Analysis on vibrational structure reveals that asymmetric meso-phenyl substitution, especially the 5,15-diphenyl substitution of ZnDPP, brings about asymmetric vibrational displacement, or even splitting of vibrational structure to normal modes involving mainly the motion of meso-C(m). This is ascribed to the reduction of symmetry of porphyrin skeleton caused by asymmetric meso-phenyl substitution.