I. V. Filatov

The Electronic Structure of Transient Species in the Photochemical Reduction of Porphyrins

Studies on the electronic structure of π-radical anions and π-dianions of Zn porphyrins, Zn chlorins, π-anions of Zn phlorins, and porphodimethenes by electronic absorption spectroscopy, luminescence, picosecond spectroscopy, ESR, NMR, IR, and Raman spectroscopy are briefly surveyed. The experimental data are compared with the results of quantum-chemical calculations. The electronic structure of M-anions with an excess charge on the central ion of a transition metal (Fe, Ni, Co, and Pd) is discussed.

Spectroscopy of the anions of tetrapyrrole compounds

We present a brief review of the results of an investigation into the electronic structure of π- and M-anions of tetrapyrrole compounds by the methods of molecular spectroscopy, namely, of electronic absorption and picosecond spectroscopy and also of IR, RRS-, EPR-, NMR1N- and NMR13S-spectroscopy. Experimental data are compared with the results of quantum-chemical calculations.

THE IMPACT OF THE PHENYL SPACER ON THE ELECTRONIC STRUCTURE AND SPECTRA OF PORPHYRIN DIMERS

Quantum-chemical investigation of the electronic structure and properties of the excited states of porphyrin dimers, in which monomeric subunits are linked by the phenyl spacer, is performed by semiempirical methods. The molecular orbitals of the monomeric subunits are shown to interact with each other via molecular orbitals of the phenyl ring. Comparison of the experimental absorption data and quantum-chemical calculations of electronic absorption spectra for different conformations of Zn-tetraphenylporphyrin dimer is performed and the main conformation of the dimer in a solution at 295 K, in which the planes of tetrapyrrole macrocycles are located at an angle of about 60°, is substantiated.

Quantum–Chemical Investigation of the Influence of Conformations and Extra–Ligation on Electronic Spectra of Chemical Dimers of Metalloporphyrins and Metallochlorins

We have made a theoretical analysis of the factors influencing the electronic absorption spectra of monomers of porphyrins and chlorins as well as of their chemically bound dimers in which the monomeric subunits are bound through the CH2–CH2 group. On the basis of quantum–chemical calculations by the semiempirical method CNDO/S it is shown that the addition of extra–ligands causes a change in the conformation of the dimers.

Molecular complexes based on tetrapyrrole compounds. Quantum-chemical investigation of the properties of excited states and conformational dynamics

On the basis of quantum-chemical calculations of the properties of excited states and comparison with the experimental data, we show that at room temperature unliganded dimers of Zn-porphyrins and Zn-chlorins, bonded through a CH2−CH2-group, are in a conformation close to an eclipsed one, while their dipyridine complexes are in an unchanged conformation. For triad and pentad complexes, formed as a result of extraliganding of dimers of Zn-porphyrins with di- and tetrapyridyl-substituted free bases of porphyrins, the calculations predict the presence of states with transfer of a charge from dimers onto a free porphyrin base that are manifested in the region between the Q- and B-transitions in electron absorption spectra.