Static polarization of the supramolecular dyads of fullerene C60 with porphyrin derivatives

The nonlinear optical properties of four supramolecular dyads consisting of fullerene C 60 non-covalently bonded to porphyrin, porphyrazine, tetrabenzoporphyrin and phthalocyanine were investigated by calculating their electronic polarizability and first- and second-order hyperpolarizabilities using the finite field method and the density functional theory with the Grimme dispersion correction. Large first- and second-order hyperpolarizabilities result in nonlinear dependence of the polarization of dyads on the strength of external electric field. The increase in the size of the π-conjugated electron system of the porphyrin analogs leads to the increase of the polarizability and first- and second-order hyperpolarizabilities of the dyads. The absence of the covalent bonds between the components of the dyads prevents the field-induced electron transfer from porphyrin analogs to fullerene. The main reason for the nonlinear behavior of the polarization of dyads is the mutual polarization of fullerene and porphyrin analogs amplified by the external electric field.

Computational study on zinc porphyrin analogs for use in dye-sensitized solar cells

The density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches have been applied to obtain the optimized geometries, electronic structures, molecular orbitals and absorption spectra of a series of meso-substituted zinc porphyrin analogs with phenyl and thiophene groups as the π bridging unit and cyanoacrylic acid as the acceptor unit. The results showed that the introduction of thiophene group increases the orbital splitting and changes the absorption spectra properties significantly. It is indicated that when there is only one thiophene group included in the π bridge, the oscillator strength of B absorption band is much stronger. The increasing length of thiophene chain just changes the scope of specific absorption enhancement. The effect of attaching an additional electron-donating group diphenylamine instead of phenyl to the porphyrin core also has been shown. It is found that the diphenylamine group reduces the band gap, and leads to facile intramolecular charge transfer from diphenylamine and porphyrin ring unit to acceptor unit. These kinds of zinc porphyrin analogs have the LUMO energy close to the conduction band of TiO 2 and more red-shifted absorption spectrum compared with phenyl substituted analogs.

Synthesis, coordination chemistry, and physico-chemical properties of the 2-chloroethoxy-iron(III)(ethylthio) porphyrazine

Reaction of octakis(ethylthio)porphyrazine ( H 2 OESPz ) with FeBr 2 in ClCH 2 CH 2 OH at 135 °C affords the 2-chloroethoxy-iron(III)-(ethylthio)porphyrazine, ( ClCH 2 CH 2 O ) Fe III OESPz , ( LFe III OESPz ) in good yield. The spectroscopic, redox, and coordination properties of the complex and its μ-oxo dimer derivative, [ Fe III OESPz ]2 O , are investigated and compared to those of the iron(III)porphyrin analogs.

Origin of aromatic character in porphyrinoid systems

The aromatic nature of porphyrins is commonly attributed to the presence of an [18]annulene substructure. However, this viewpoint has been disputed. Drawing on a range of examples of carbaporphyrinoid systems from the author's own studies, the [18]annulene model is shown to be a self-consistent and insightful approach for considering the aromatic properties of these porphyrin analogs. Benziporphyrins provide a continuum of porphyrinoid structures that range from nonaromatic to highly aromatic species and the presence of 18π electron delocalization pathways provides an excellent explanation for the variations in their properties. The same type of analysis is applied to carbaporphyrins, tropiporphyrins, azuliporphyrins, N-confused porphyrins, pyrazoloporphyrins and dicarbaporphyrins. Nevertheless, these properties might also be explained by a 22π electron delocalization model proposed by Schleyer. The [18]annulene model gains further support from the properties of dideazaporphyrins which cannot take part in this type of 22π electron delocalization but nevertheless retain porphyrin-like aromatic properties. These results support the concept that porphyrins are bridged [18]annulenes.

Modifying the porphyrin core — a chemist's jigsaw

Core modified porphyrinoids are porphyrin analogs which differ from these by containing at least one non-pyrrolic aromatic ring. The result of core modification is to produce systems with novel and unique physical and electronic properties. In this review, the various possible core modified porphyrins and their syntheses are summarized starting by porphyrinoids with one pyrrolic nitrogen replaced followed by porphyrin-related macrocycles with two or more pyrrole rings exchanged. In addition the spectroscopic properties, especially the UV-vis absorption profiles and proton NMR shifts emanating from their core modifications are discussed and summarized in a table.

Porphyrin analogs bearing exocyclic double bonds at meso-positions: bis(meso-diethylmalonylidene)-(1,4-naphthi)thiaporphyrin

meso-diethylmalonylidene-(1,4-naphthi)thiaporphyrin containing exocyclic C – C double bonds at meso-positions has been synthesized and characterized. The compound undergoes initial protonation at the α-position of the diethylmalonyl group with large red shifted absorption maxima. The second protonation occurs at a meso-position to give a species with broken cross-conjugation.