title: Furan- and selenophene-2-carboxylato derivatives of dimolybdenum and ditungsten (M[quadruple bond]M): a comparison of their chemical and photophysical properties.
abstract: From the reactions between M(2)(T(i)PB)(4), where T(i)PB = 2,4,6-triisopropylbenzoate and two equivalents each of 2-furan carboxylic acid, FuCO(2)H, and 2-selenophene carboxylic acid, SpCO(2)H in toluene, the new compounds trans-M(2)(T(i)PB)(2)(O(2)CFu)(2) (1a M = Mo, 2a M = W) and trans-M(2)(T(i)PB)(2)(O(2)CSp)(2) (1b M = Mo, 2b M = W) were formed. These new compounds have been characterized by (1)H NMR, steady-state UV-Vis-NIR absorption and emission spectroscopy, cyclic and differential pulse voltammetry, and fs and ns transient absorption spectroscopy. The compound Mo(2)(T(i)PB)(2)(O(2)CSp)(2) (1b) has been characterized by single crystal X-ray crystallography. These data are compared with those previously reported for related 2-thiophene carboxylate derivatives: M(2)(T(i)PB)(2)(O(2)CTh)(2). The physico-chemical data correlate well with electronic structure calculations performed on model compounds. All compounds have detectible S(1) photoexcited states with lifetimes that vary from ∼5 ps to < 1 ps. The molybdenum compounds have T(1) states with microsecond lifetimes that are assigned as MMδδ* whereas the T(1) states for tungsten are (3)MLCT with lifetimes on the order of nanoseconds. In all cases, shorter lifetimes were seen in complexes containing heavier atoms.
authors.affiliation: Department of Chemistry, The Ohio State University, 100 W 18th Ave., Columbus, Ohio 43210, USA.
authors.forename: Samantha E
authors.initials: SE
authors.lastname: Brown-Xu
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
authors.forename: Carly R
authors.initials: CR
authors.lastname: Reed