Electron spin resonance and polarization spectra of oxovanadium(IV) porphyrins oriented in stretched PVA films

Abstract
Polarizations of the electronic transitions in metalloporphyrins were determined by polarized absorption measurements on poly(vinyl alcohol) films dyed with oxovanadium(IV) complexes of tetra(4-sulphophenyl)porphin being stretched in one direction within the plane of the polymer film. The stretching gives rise to a uniaxial orientational distribution of the disclike molecules. The E.S.R. spectra taken with the identical stretched films support the uniaxial distribution. The orientational distribution was determined by comparing the angular dependence of the observed E.S.R. line-shape with that calculated by a computer program developed for the numerical deconvolution of E.S.R. spectra of the partially ordered paramagnetic ensemble. The best fit distribution function was a long tailing function such as lorentzian rather than gaussian and could reasonably reproduce the optical polarization. The E.S.R. parameters of CuTPPS4 were also evaluated by analysis of the complicated spectra of CuTPPS4 observed partially oriented in the stretched PVA film.

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