title: Quadruply bonded dimetal units supported by 2,4,6-triisopropylbenzoates MM(TiPB)(4) (MM = Mo(2), MoW, and W(2)): preparation and photophysical properties.
abstract: The preparation and characterization (elemental analysis, (1)H NMR, and cyclic voltammetry) of the new compounds MM(TiPB)(4), where MM = MoW and W(2) and TiPB = 2,4,6-triisopropylbenzoate, are reported. Together with Mo(2)(TiPB)(4), previously reported by Cotton et al. (Inorg. Chem. 2002, 41, 1639), the new compounds have been studied by electronic absorption, steady-state emission, and transient absorption spectroscopy (femtosecond and nanosecond). The compounds show strong absorptions in the visible region of the spectrum that are assigned to MMdelta to arylcarboxylate pi* transitions, (1)MLCT. Each compound also shows luminescence from two excited states, assigned as the (1)MLCT and (3)MMdeltadelta* states. The energy of the emission from the (1)MLCT state follows the energy ordering MM = Mo(2) > MoW > W(2), but the emission from the (3)MMdeltadelta* state follows the inverse order: MM = W(2) > MoW > Mo(2). Evidence is presented to support the view that the lower energy emission in each case arises from the (3)MMdeltadelta* state. Lifetimes of the (1)MLCT states in these systems are approximately 0.4-6 ps, whereas phosphorescence is dependent on the MM center: Mo(2) approximately 40 micros, MoW approximately 30 micros, and W(2) approximately 1 micros.
authors.affiliation: Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 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: Yi-Hsuan
authors.initials: YH
authors.lastname: Chou
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: Nathan J
authors.initials: NJ
authors.lastname: Patmore
authors.forename: Carly R
authors.initials: CR
authors.lastname: Reed
authors.forename: Claudia
authors.initials: C
authors.lastname: Turro