title: Transition Metal Substitution Effects on Metal-to-Polyoxometalate Charge Transfer.
abstract: A series of hetero-bimetallic transition metal-substituted polyoxometalates (TMSPs) were synthesized based on the Co(II)-centered ligand [Co(II)W11O39](10-). The eight complex series, [Co(II)(M(x)OHy)W11O39]((12-x-y)-) (M(x)OHy = V(IV)O, Cr(III)(OH2), Mn(II)(OH2), Fe(III)(OH2), Co(II)(OH2), Ni(II)(OH2), Cu(II)(OH2), Zn(II)(OH2)), of which six are reported for the first time, was synthesized starting from [Co(III)W11O39](9-) and studied using spectroscopic, electrochemical, and computational techniques to evaluate the influence of substituted transition metals on the photodynamics of the metal-to-polyoxometalate charge transfer (MPCT) transition. The bimetallic complexes all show higher visible light absorption than the plenary [Co(II)W12O40](6-) and demonstrate the same MPCT transition as the plenary complex, but they have shorter excited-state lifetimes (sub-300 ps in aqueous media). The decreased lifetimes are rationalized on the basis of nonradiative relaxation due to coordinating aqua ligands, increased interaction with cations due to increased negative charge, and the energy gap law, with the strongest single factor appearing to be the charge on the anion. The most promising results are from the Cr- and Fe-substituted systems, which retain excited-state lifetimes at least 50% of that of [Co(II)W12O40](6-) while more than tripling the absorbance at 400 nm.
authors.affiliation: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University , Atlanta, Georgia 30322, United States.
authors.forename: Elliot N
authors.initials: EN
authors.lastname: Glass
authors.affiliation: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University , Atlanta, Georgia 30322, United States.|WestCHEM, School of Chemistry, University of Glasgow , Glasgow G12 8QQ, United Kingdom.|School of Chemistry, University of East Anglia , Norwich NR4 7TJ, United Kingdom.
authors.forename: John
authors.initials: J
authors.lastname: Fielden
authors.affiliation: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University , Atlanta, Georgia 30322, United States.
authors.forename: Zhuangqun
authors.initials: Z
authors.lastname: Huang
authors.affiliation: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University , Atlanta, Georgia 30322, United States.|State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology , Beijing 100029, P. R. China.
authors.forename: Xu
authors.initials: X
authors.lastname: Xiang
authors.affiliation: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University , Atlanta, Georgia 30322, United States.
authors.forename: Djamaladdin G
authors.initials: DG
authors.lastname: Musaev
authors.affiliation: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University , Atlanta, Georgia 30322, United States.
authors.forename: Tianquan
authors.initials: T
authors.lastname: Lian
authors.affiliation: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University , Atlanta, Georgia 30322, United States.
authors.forename: Craig L
authors.initials: CL
authors.lastname: Hill
mesh_terms: D003035:Cobalt / Q000737:chemistry; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D055664:Electrochemical Techniques; D007700:Kinetics; D008027:Light; D019216:Metals, Heavy / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D010087:Oxides / Q000138:chemical synthesis / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D014414:Tungsten / Q000737:chemistry
chemical_list: D056831:Coordination Complexes; D019216:Metals, Heavy; D010087:Oxides; D003035:Cobalt; D014414:Tungsten