title: Electron delocalization in the S1 and T1 metal-to-ligand charge transfer states of trans-substituted metal quadruply bonded complexes.
abstract: The singlet S(1) and triplet T(1) photoexcited states of the compounds containing MM quadruple bonds trans-M(2)(T(i)PB)(2)(O(2)CC(6)H(4)-4-CN)(2), where T(i)PB = 2,4,6-triisopropylbenzoate and M = Mo (I) or M = W (I(')), and trans-M(2)(O(2)CMe)(2)((N[(i) Pr ])(2)CC ≡ CC(6)H(5))(2), where M = Mo (II) and M = W (II(')), have been investigated by a variety of spectroscopic techniques including femtosecond time-resolved infrared spectroscopy. The singlet states are shown to be delocalized metal-to-ligand charge transfer (MLCT) states for I and I(') but localized for II and II(') involving the cyanobenzoate or amidinate ligands, respectively. The triplet states are MoMoδδ* for both I and II but delocalized (3)MLCT for I(') and localized (3)MLCT for II('). These differences arise from consideration of the relative orbital energies of the M(2)δ or M(2)δ* and the ligand π(∗) as well as the magnitudes of orbital overlap.
authors.affiliation: Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210-1185, USA.
authors.forename: Brian G
authors.initials: BG
authors.lastname: Alberding
authors.forename: Malcolm H
authors.initials: MH
authors.lastname: Chisholm
authors.forename: Judith C
authors.initials: JC
authors.lastname: Gallucci
authors.forename: Yagnaseni
authors.initials: Y
authors.lastname: Ghosh
authors.forename: Terry L
authors.initials: TL
authors.lastname: Gustafson