Resonance Raman, fluorescence, and phosphorescence of palladium phthalocyanine in Shpol’skii matrices

Abstract

The degenerate states of the first excited singlet and triplet of palladium phthalocyanine (PdPc) in Shpol’skii matrices at 4.2 K are lifted 67±2 cm−1 by the crystal field stabilized Jahn–Teller effect. Strengths of emission from the split triplets follow the Boltzmann relation, whereas those from the split singlets do not. The singlet and triplet emission yields and lifetimes indicate a reduction of nonradiative rates in Shpol’skii matrices as compared to those in alpha-chloronaphthalene (αCIN) observed previously. The concurrence of resonance Raman and relaxed fluorescence from the singlets in this system was verified from the study of the emission spectra. In deexcitation, it was found that the incoherent resonance fluorescences was insignificant as compared with the coherent resonance Ramans and, for some fundamental vibrations, the intersystem crossing (ISC) processes were not negligible. The vibronic spectra in emission and excitation are characterized by very weak intra- and interstate vibronic interaction and electron–phonon interaction as usual for metal Pc’s in Shpol’skii matrices. The absence of mirror symmetry between absorption and fluorescence for the totally symmetric vibrations, except the 1536 cm−1 fundamental, was found and could be attributed to the non-Condon effect induced by the vibronic interaction. The enhancement in the intensity of phosphorescence excitation over the fluorescence excitation and the appearance of extra vibronic bands in phosphorescence were observed and successfully explained.