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Inter- and intramolecular processes in metalloporphyrins: study by transient absorption and resonance Raman and coherent anti-Stokes Raman scattering
Author(s): Pavel A. Apanasevich; Vladimir S. Chirvony; Sergei G. Kruglik; Vladimir V. Kvach; Valentin A. Orlovich
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Paper Abstract

The steady interest in metalloporphyrins (Me-P) which have a central metal with an unfilled d-electronic shell is due to the rich variety of photoinduced physico-chemical processes they participate in, and by the possibility of modelling on the basis of them, the behavior of related native biological complexes. Me-Ps with an unfilled d-shell of the central atom have typical two-band absorption spectra in the ground electronic state: intense Soret or B band in the near UV and less intense Q band in the visible. According to Gouterman's fourorbital model,' the Me-P absorption spectrum arises from the promotion of ir-electrons from the highest occupied molecular orbitals a, , a2 to the lowest unoccupied orbitals e of the porphyrin conjugated macrocycle. The a, and a2 orbitals are quasi-degenerate and the electron excited configurations e have the same symmetry. That is why there is a strong mixing between the two orbital excitations a, -e and a, - e due to the configurational interaction via the electron-electron repulsion, resulting in a two-band absorption spectrum. The effect of the central atom is interpreted in this model as a perturbation of the ir-states of the porphyrin ring. The perturbation is largely determined by the electrons of the unfilled shells of the metal ion (e.g. the md'-shell). This effect is quite pronounced for the ground electronic state, nevertheless the interactions of excited ir-electronic configurations with d-electron ones cause more dramatic changes in the spectroscopic properties of Me-P excited states. New low-lying excited states are possible: the charge-transfer (CT) levels related to the electrodensity transfering from the ring a, , a2 to the d-orbitals of central metal (ir-d states) or from the d-orbitals to the ring e(d - ir states), and (d - d) levels bound up with the d-electron excitations. The present paper deals with the investigations of porphyrin metallocomplexes with nickel (Ni-P) and copper (Cu-P) having electron configurations 3d8 and 3d9 , respectively.

Paper Details

Date Published: 1 May 1991
PDF: 17 pages
Proc. SPIE 1403, Laser Applications in Life Sciences, (1 May 1991); doi: 10.1117/12.57272
Show Author Affiliations
Pavel A. Apanasevich, B. I. Stepanov Institute of Physics (Belarus)
Vladimir S. Chirvony, B. I. Stepanov Institute of Physics (Belarus)
Sergei G. Kruglik, B. I. Stepanov Institute of Physics (Belarus)
Vladimir V. Kvach, B. I. Stepanov Institute of Physics (Belarus)
Valentin A. Orlovich, B. I. Stepanov Institute of Physics (Belarus)

Published in SPIE Proceedings Vol. 1403:
Laser Applications in Life Sciences
Sergei A. Akhmanov; Marina Yu. Poroshina, Editor(s)

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