A. Bencini et al., Ground and excited state properties and vibronic coupling analysis of the Creutz-Taube ion, C[(NH3)(5)Ru-pyridine-Ru(NH3)(5)](5+), using DFT, J AM CHEM S, 121(49), 1999, pp. 11418-11424
In this paper we analyze using Density Functional Theory (DFT) the electron
ic structure of the Creutz-Taube ion, [(NH3)(5)Ru-pyrazine-RU(NH3)(5)](5+),
a classical example of a mixed-valence complex. A complete structural and
bonding analysis, description of the low-lying excited states, and a vibron
ic coupling calculation along both the symmetric and the antisymmetric Ru-p
yrazine-Ru stretching mode are presented. The results are in very good agre
ement with the reported experimental data and we are able to assign unambig
uously this compound as a Class III system, following the Robin and Day cla
ssification. In this work we demonstrate that DFT does offer a unique tool
for handling the localization-delocalization of electrons in mixed-valence
systems and therefore we expect that this approach can play an important ro
le in characterizing electron-transfer systems. Localized Ru-N(pyrazine) st
retching in the range 254-275 cm(-1) has been estimated from our calculatio
ns, which should be used in future model Hamiltonians which aim to include
the Ru-pyz bond vibration to describe the spectral features of the Creutz-T
aube ion.