title: Vibronic interaction in metalloporphyrin pi-anion radicals.
abstract: The vibronic (vibrational-electronic) interactions in the pi-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 2Eg state of the pi-anion radicals in the D4h symmetric structures to lead to rectangular and diamond D2h distortions, respectively. Calculated vibronic coupling constants demonstrate that the B1g modes of vibration better couple with the degenerate electronic state, leading to the rectangular D2h distortion. In particular, the B1g modes of nu10 and nu11, which have dominant contributions from Calpha-Cm and Cbeta-Cbeta stretching, give large vibronic coupling constants in the pi-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 pi-anion radicals of the metalloporphyrins.
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 812-8581, Japan. kazunari@ms.ifoc.kyushu-u.ac.jp
authors.forename: Kazunari
authors.initials: K
authors.lastname: Yoshizawa
authors.forename: Tomonori
authors.initials: T
authors.lastname: Nakayama
authors.forename: Takashi
authors.initials: T
authors.lastname: Kamachi
authors.forename: Pawel M
authors.initials: PM
authors.lastname: Kozlowski
mesh_terms: D000838:Anions / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D008665:Metalloporphyrins / Q000737:chemistry*; D019216:Metals, Heavy / Q000737:chemistry*; D008956:Models, Chemical; D014732:Vibration
chemical_list: D000838:Anions; D005609:Free Radicals; D008665:Metalloporphyrins; D019216:Metals, Heavy