Resonance Raman in platinum phthalocyanine

Abstract
The resonance Raman spectra and excitation profiles of platinum phthalocyanine (PtPc) in α-chloronaphthalene (α-ClN) and in mixtures of α-ClN and n-octane were obtained at 295 K with excitation from 660 to 570 nm covering the total lower energy absorption region of PtPc. Eighteen fundamentals and overtone-combinations were observed. Our data show that the third absorption maximum of PtPc in the visible region is actually the (0–1), but not the (0–2) as previously interpreted, transition. The (0–1) bands in the excitation profiles of most resonance-enhanced-vibrations were found to be more intense and frequency shifted compared with their counterparts in absorption. Based on the depolarization ratios, we deduced the symmetry of PtPc in α-ClN in the excited singlets to be D2h, C2v, or D2; no differences were found in the mixed solvents. The small Stokes loss observed in the absorption spectra, as well as the absence of the (0–2) maxima in the excitation profiles, indicate that the equilibrium position of the first excited singlet is only slightly different from that of the ground state.