Density functional study of valence trapping in a mixed-valent dimanganese complex

Density functional calculations are reported for the linked system [(Fulv)[Mn(CO)(2)](2)(mu-dppm)] in the neutral and singly and doubly charged states. The neutral system and dication are characterized by well-localized valence states involving two Mn(II) and Mn(I) centers, respectively. At the BP86/AE1 level, the electronic structure of the monocation is that of a delocalized mixed-valence species. At the B3LYP/AE1 level, the spin density of the unpaired electron is largely localized on one Mn atom, in accord with the formulation of a trapped-valence ground state (Atwood, C. G.; Geiger, W. E. J. Am. Chem. Soc. 2000, 122, 5477). The qualitative IR pattern of the CO stretching vibrations is well reproduced at the B3LYP level, supporting the empirical charge distribution parameter employed for the interpretation of the IR spectra.