Resonance hyper-Raman spectra of zinc phthalocyanine

作者：Leng Weinan; Kelley Anne Myers^*

来源：Journal of Physical Chemistry A, 2008, 112(26): 5925-5929.

DOI：10.1021/jp801016q

Hyper-Raman spectra were obtained for zinc phthalocyanine in a dilute pyridine solution at excitation wavelengths that are two-photon resonant with the one-photon-allowed B band (360-380 nm) as well as with the two-photon absorption near 440 nm reported by Drobizhev et al. (J. Chem. Phys. 2006, 124, 224701). In both regions, the hyper-Raman spectra were very different from the linear resonance Raman spectra at the corresponding excitation frequencies. While the resonance Raman spectra show only g symmetry modes, almost all of the hyper-Raman frequencies. can be assigned as fundamentals of E,, symmetry that also are observed in the infrared absorption spectrum or E. symmetry combination bands. These results contrast sharply with previous observations of highly noncentrosymmetric push-pull conjugated molecules and are consistent with a structure for phthalocyanine in solution that is centrosymmetric or nearly so. The hyper-Raman spectra show different intensity patterns in the two excitation regions, consistent with different Franck-Condon and/or vibronic coupling matrix elements for the different resonant states.

• 出版日期2008-7-3