Theoretical analysis of the structural and electronic properties of metalloporphyrin π-cation radicals

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Original languageEnglish
Pages (from-to)6091-6099
Journal / PublicationJournal of Physical Chemistry A
Issue number18
Publication statusPublished - 11 May 2006
Externally publishedYes


A method for analyzing the A 1u/A 2u contents of metalloporphyrin π-cation radicals is developed and applied to a series of unsubstituted planar metalloporphines (MPs) (M = Cr, Mn, Fe, Co, Ni, Cu, and Zn). The structures and electronic properties of the MPs and their cation radicals were calculated by density functional theory (DFT) and subsequently analyzed. It was found that the MPs with small core sizes have a tendency to form A 1u-type radicals, while the MPs with large core size have a preference for an A 2u-type. Neither of these pure-state species, however, is stable under the D 4h symmetry, and both radical cation types are subject to pseudo-Jahn - Teller (pJT) distortion. The pJT distortion leads to structures with lower symmetry and states that have mixed character with respect to the A 1u and A 2u components. The degree of mixing could be estimated by employing orbital projection technique or a complementary spin density decomposition. Both techniques produce very similar results, pointing out that the frontier orbital, which becomes empty upon electron removal, plays a critical role in determining electronic properties. © 2006 American Chemical Society.

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