Resonance Raman spectra of N-deprotonated sigma-type dianion of porphycenes.

Resonance Raman spectra of N-deprotonated sigma-type dianion of porphycenes were measured in an effort to characterize the structural changes concomitant with N-deprotonation. The observed resonance Raman behavior was consistent with the results of vibrational analysis by quantum chemical calculations based on density functional theory methods. Resonance Raman behavior predicted an expanded porphycene core for N-deprotonated sigma-type dianion with elongation of peripheral bond lengths. This sigma-type dianion is distinctive from pi-type dianion which has an expanded core with alternating changes in peripheral bond lengths.