title: Substitution of the terminal chloride ligands of [Re(6)S(8)Cl(6)](4-) with triethylphosphine: photophysical and electrochemical properties of a new series of [Re(6)S(8)](2+) based clusters.
abstract: A systematic substitution of the terminal chlorides coordinated to the hexanuclear cluster [Re(6)S(8)Cl(6)](4-) has been conducted. The following complexes: [Re(6)S(8)(PEt(3))Cl(5)](3-) (1), cis- (cis-2) and trans-[Re(6)S(8)(PEt(3))(2)Cl(4)](2-) (trans-2), mer- (mer-3) and fac-[Re(6)S(8)(PEt(3))(3)Cl(3)](-) (fac-3), and cis- (cis-4) and trans-[Re(6)S(8)(PEt(3))(4)Cl(2)] (trans-4) were synthesized and fully characterized. Compared to the substitution of the halide ligands of the related [Re(6)S(8)Br(6)](4-) and [Re(6)Se(8)I(6)](3-) clusters, the chloride ligands are slower to substitute which allowed us to prepare the first monophosphine cluster (1). In addition, the synthesis of fac-3 was optimized by using cis-2 as the starting material, which led to a significant increase in the overall yield of this isomer. Notably, we observed evidence of phosphine isomerization taking place during the preparation of the facial isomer; this was unexpected based on the relatively inert nature of the Re-P bond. The structures of Bu(4)N(+) salts of trans-2, mer-3, and fac-3 were determined using X-ray crystallography. All compounds display luminescent behavior. A study of the photophysical properties of these complexes includes measurement of the excited state lifetimes (which ranged from 4.1-7.1 μs), the emission quantum yields, the rates of radiative and non-radiative decay, and the rate of quenching with O(2). Quenching studies verify the triplet state nature of the excited state.
authors.affiliation: Department of Chemistry, Illinois State University, Normal, Illinois 61790-4160, United States. lfszcze@ilstu.edu
authors.forename: Lisa F
authors.initials: LF
authors.lastname: Szczepura
authors.forename: David L
authors.initials: DL
authors.lastname: Cedeño
authors.forename: Dean B
authors.initials: DB
authors.lastname: Johnson
authors.forename: Robert
authors.initials: R
authors.lastname: McDonald
authors.forename: Stanley A
authors.initials: SA
authors.lastname: Knott
authors.forename: Kristen M
authors.initials: KM
authors.lastname: Jeans
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Durham