Zinc Tetraphenylporphyrin Complex Research Articles

Ultrafine Fibers of Poly-(3-Hydroxybutyrate) with Zinc–Tetraphenylporphyrin Obtained by Electrospinning

Ultrathin fibers of poly(3-hydroxybutyrate) (PHB) with a zinc–tetraphenylporphyrin complex (0-5%) were obtained by electrospinning. Optical microscopy, differential scanning calorimetry, electron paramagnetic resonance, and x-ray structural analysis were used to study the structure of the fibers. It was shown that addition of the ZnTPP complex to the PHB fiber increases the crystallinity and lowers the molecular mobility in the amorphous regions of the polymer. The action of heat on the fiber (annealing at 140°C) leads to significant increase of crystallinity and molecular mobility in the amorphous regions of fibers of PHB and of PHB with 1% of ZnTPP. With 3-5% content of the complexes the crystallinity of the fiber is substantially reduced. The results of the work make it possible to recommend the investigated materials for biomedical application as matrices with antibacterial activity

Coordination of zinc tetraphenylporphyrin with pyridine derivatives in chloroform solution and in the solid phase

Coordination of zinc tetraphenylporphyrin with 2-,3-, and 4-halopyridines, pyridin-2-amine, and pyrimidin-2-amine in chloroform has been studied by spectrophotometry. Protonation and complexation of halopyridines and haloanilines with zinc tetraphenylporphyrin are discussed. According to the X-ray diffraction data, enhanced stability of the 2: 2 zinc tetraphenylporphyrin complex with pyrimidin-2-amine in the solid phase and in chloroform solution is likely to be determined by hydrogen bonding between the two ligand molecules involving nitrogen atoms in the pyrimidine ring and amino group.

A negligible CT character of the lowest excited state of a novel complex of zinc tetraphenylporphyrin with axially bonded 2-(4-methoxy-trans-styryl)quinoline-1-oxide ligand: Experimental studies and TD DFT/CAM B3LYP [6-31G(d,p)] calculations

Abstract The crystal structure and photophysical behavior of the novel (1:1) ZnTPP–MSQNO complex composed of ZnTPP unit with axially bonded 2-(4-methoxy-trans-styryl)quinoline-1-oxide ligand (MSQNO) has been extensively investigated both in solution and in the solid state. The single-crystal X-ray measurements, stationary absorption and emission spectra and the time-resolved fluorescence spectroscopy combined with TD DFT/CAM B3LYP [6-31G(d,p)] calculations were employed. The crystal structure is characterized by the centrosymmetric triclinic unit cell, space group P 1 ¯ . Zinc atom in the studied complex is pulled out 0.365 A from the porphyrin macrocycle and the MSQNO ligand occurs in the anti-rotameric form of the trans-isomer. The complex formation in the solution is confirmed by the appropriate red shift of the Qx and Qy band in the absorption spectrum in toluene, which is in a good agreement with the results obtained by theoretical calculations. We have found that effective mixing of electronic configurations of the locally excited states with those of the charge transfer type leads to a negligible CT nature of the S1 state of ZnTPP–MSQNO complex. We also hypothesized, that due to an overlap of the absorption spectrum of MSQNO and ZnTPP in the Soret band region, the electronic coupling becomes possible and the nonradiative energy transfer process as an additional deactivation channel may take place. An unusually short lifetime (0.6 ns) was revealed for the solid complex, while in toluene (1.5 ns) and in n-propanol (2.7 ns), they shown to be several times longer.

Direct probing of photoinduced electron transfer in a self-assembled biomimetic [2Fe2S]-hydrogenase complex using ultrafast vibrational spectroscopy.

A pyridyl-functionalized diiron dithiolate complex, [μ-(4-pyCH2-NMI-S2)Fe2(CO)6] (3, py = pyridine (ligand), NMI = naphthalene monoimide) was synthesized and fully characterized. In the presence of zinc tetraphenylporphyrin (ZnTPP), a self-assembled 3·ZnTPP complex was readily formed in CH2Cl2 by the coordination of the pyridyl nitrogen to the porphyrin zinc center. Ultrafast photoinduced electron transfer from excited ZnTPP to complex 3 in the supramolecular assembly was observed in real time by monitoring the ν(C≡O) and ν(C═O)NMI spectral changes with femtosecond time-resolved infrared (TRIR) spectroscopy. We have confirmed that photoinduced charge separation produced the monoreduced species by comparing the time-resolved IR spectra with the conventional IR spectra of 3(•-) generated by reversible electrochemical reduction. The lifetimes for the charge separation and charge recombination processes were found to be τCS = 40 ± 3 ps and τCR = 205 ± 14 ps, respectively. The charge recombination is much slower than that in an analogous covalent complex, demonstrating the potential of a supramolecular approach to extend the lifetime of the charge-separated state in photocatalytic complexes. The observed vibrational frequency shifts provide a very sensitive probe of the delocalization of the electron-spin density over the different parts of the Fe2S2 complex. The TR and spectro-electrochemical IR spectra, electron paramagnetic resonance spectra, and density functional theory calculations all show that the spin density in 3(•-) is delocalized over the diiron core and the NMI bridge. This delocalization explains why the complex exhibits low catalytic dihydrogen production even though it features a very efficient photoinduced electron transfer. The ultrafast porphyrin-to-NMI-S2-Fe2(CO)6 photoinduced electron transfer is the first reported example of a supramolecular Fe2S2-hydrogenase model studied by femtosecond TRIR spectroscopy. Our results show that TRIR spectroscopy is a powerful tool to investigate photoinduced electron transfer in potential dihydrogen-producing catalytic complexes, and that way to optimize their performance by rational approaches.

A novel complex of zinc tetraphenylporphyrin with two dioxane molecules in a rare attachment. Crystal structure, spectroscopy and theoretical calculations

We have shown the X-ray crystal structure of a novel ZnTPP–(Dioxane)2 complex and the results of solution studies by means of steady state absorption and fluorescence as well as time-resolved fluorescence techniques complemented by theoretical DFT and TD DFT B3LYP/6-31G(d,p) calculations. The ZnTPP–(Dioxane)2 crystallizes in centrosymmetric monoclinic unit cell, space group P21/c and shows a unique structure, with two dioxane molecules in “chair” conformation, placed in equatorial and axial position relative to ZnTPP core. Analysis of TD DFT B3LYP/6-31G(d,p) wave functions of ZnTPP–(Dioxane)2, allowed us to describe the nature of particular electronic transitions and to identify two bands (LE, CT) absent in its components. The former, results from the symmetry reduction of ZnTPP and the latter, from a mixed character of the HOMO (220) orbital of the complex. A red shift of the Soret and the Q band found in absorption and fluorescence spectra indicating the complex formation in solution is confirmed by the simulated absorption spectra of ZnTPP–(Dioxane)2 relative to ZnTPP unit both in the gas phase and in dioxane solution by PCM model. The estimated lifetime of the complex (1.75ns) is shorter than that of free ZnTPP unit (∼2ns).

Photoinduced electron transfer in pentacoordinated complex of zinc tetraphenylporphyrin and isoquinoline N-oxide. Crystal structure, spectroscopy and DFT studies

A novel, pentacoordinated complex of (1:1) zinc tetraphenylporphyrin and isoquinoline N-oxide (ZnTPP–IQNO) was synthesized and its crystal structure along with photophysical properties by experimental methods (absorption, steady state and time-resolved emission) in conjunction with DFT and TD DFT calculations were investigated. In ZnTPP–IQNO complex, the isoquinoline N-oxide ligand (IQNO) is directly coordinated to the central zinc atom of the ZnTPP unit through the oxygen atom of the NO group and crystallizes in centrosymmetric triclinic unit, in the space group P 1 ¯ . Particular contacts between the two monomeric units (hydrogen bonds, O ⋯ H–C interactions, …etc.) lead to a supramolecular dimer which forms the layers propagating both along the a and the b-axis. The electronic locally excited and the charge-transfer states of the complex were calculated by TDDFT CAM-B3LYP/6-31G(d,p) method. A surprising presence of the charge transfer states between the Soret and the Q bands leads to excitation energy dissipation processes involving the opening of the radiationless channels of excited ZnTPP–IQNO complex. Emission from the S 1 state (Q band) in ethyl acetate decays accordingly to monoexponential function (1.92 ns) while a bi-exponential decay is found in n-propanol [(2.5 ns (87%); 14.4 ns (13%)] and in the solid state [1.36 ns (67.5%), 7.31 ns (32.5%)].

β-Substitution de la méso-tétraphénylporphyrine de zinc par voie électrochimique

The electrochemical oxidation of the zinc tetraphenylporphyrin complex in a mixed acetonitrile–dichloroethane solution in the presence of nucleophiles (Py, 3-Pic, [Formula: see text], SCN−) leads to the formation of the corresponding monosubstituted metalloporphyrin. For each of these nucleophiles the substitution occurs at a pyrrole carbon atom (β-substitution). The electrochemical conditions of these substitutions are discussed and an overall reaction is proposed. Key words: porphyrins, electrochemical reactions, nucleophilic substitution.

Kinetics of charge transfer from zinc tetraphenylporphyrin to an axially co-ordinated pyridine

The aromatic radical anion charge transfer state of a pyridine–zinc tetraphenylporphyrin complex is formed in good yield with a time constant of 3 ns following generation of the porphyrin triplet.