title: Distinguishing the strength of electronic coupling for Mo2 -containing mixed-valence compounds within the Class III regime.
abstract: Two, symmetrical, mixed-valence (MV), complex cations-{[Mo2 (DAniF)3 ]2 (μ-oxamidate)}(+) (1(+) ) and {Mo2 (DAniF)3 ]2 (μ-dithiooxamidate)}(+) (2(+) ; DAniF=N,N'-di(p-anisyl)formamidinate)-are significantly differentiated in terms of electronic coupling between the two [Mo2 ] units. For 1(+) the intervalence (IV) charge-transfer band in the near-IR spectrum is truncated in half on the low-energy side as predicted for MV compounds at the Class II-III limit (2Hab /λ=1; for which Hab =electronic coupling matrix element and λ=reorganization energy). In contrast, the very strongly coupled analogue 2(+) , as indicated by 2Hab /λ=3.5 (> >1), exhibits a higher energy and more symmetrical IV band. As rare examples, this pair of MV species shows distinct optical behaviors for MV systems crossing the Class III region. Optical analysis and DFT calculations are carried out to elucidate the transformation from vibronic to electronic vertical transition.
authors.affiliation: Department of Chemistry, Jinan University, 601 Huang-Pu Avenue West, Guangzhou (P.R. China).
authors.forename: Tao
authors.initials: T
authors.lastname: Cheng
authors.forename: Ying Ning
authors.initials: YN
authors.lastname: Tan
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yu Yu
authors.initials: YY
authors.lastname: Zhang
authors.forename: Miao
authors.initials: M
authors.lastname: Meng
authors.forename: Hao
authors.initials: H
authors.lastname: Lei
authors.forename: Lu
authors.initials: L
authors.lastname: Chen
authors.forename: Chun Y
authors.initials: CY
authors.lastname: Liu
keywords: electronic coupling; intervalence transitions; metal-metal bonds; mixed valency; two-state models