Spectral manifestation of distorted forms of metalloporphins in solid matrices

Abstract

In this paper we report the spectral manifestation of different spectral forms obtained for Mg-, Zn-, Pd- and Pt-porphins in solid matrices (Shpol'skii matrices, solid tetrahydrofuran and rare gas matrices) at cryogenic temperatures. The planar and two kinds of distorted conformations of Mg-, Zn-porphins in highly-resolved fluorescence spectra have been detected. For Zn-porphin distorted forms have been detected in the fluorescence and phosphorescence spectra simultaneously. In the phosphorescence spectra of the Pd- and Pt-porphins the manifestation of the two forms in the ground state has been proved also. Energy splitting in the phosphorescence spectrum of the Pd-porphin in <i>n-</i>octane at 4,2 K comes to 78 cm^-1 for two forms of the Pd-porphin. Under selective excitation in S₀-S₁ channel the large set of sharp lines was detected for each of two forms and vibrational frequencies have been determined. In highly-resolved phosphorescence spectra of Pt-porphin in <i>n-</i>octane at 4,2 K we have detected similar manifestation of the two spectral forms in the phosphorescence spectrum. To estimate the type of molecule distortion the information about the frequencies of vibronic modes from well-resolved spectra of metalloporphins have been used.