The vibronic (vibrational-electronic) interactions in the π-anion radicals of the metalloporphyrins (M=Cr, Mn, Fe, Co, Ni, Cu, and Zn), which show delocalized D4h structures in the neutral states, are discussed using B3LYP density-functional-theory calculations. The B1g and B2g modes of vibration can remove the degenerate 2E g state of the π-anion radicals in the D4h symmetric structures to lead to rectangular and diamond D2h distortions, respectively. Calculated vibronic coupling constants demonstrate that the Big modes of vibration better couple with the degenerate electronic state, leading to the rectangular D2h distortion. In particular, the Big modes of v10 and v11, which have dominant contributions from C α-Cm and Cβ-Cβ stretching, give large vibronic coupling constants in the π-anion radicals. The vibronic coupling constant can be viewed as the Jahn-Teller distortion force, and therefore these C-C stretching B1g modes will play a central role in the Jahn-Teller effect of the π-anion radicals of the metalloporphyrins.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry