Experimental and theoretical investigations of the sulfite-based polyoxometalate cluster redox series:: α- and β-[Mo18O54(SO3)2]4-15-16-

被引:47
作者
Baffert, Carole
Boas, John F.
Bond, Alan M. [1 ]
Kogerler, Paul
Long, De-Liang
Pilbrow, John R.
Cronin, Leroy
机构
[1] Monash Univ, Sch Chem, Clayton, Vic 3800, Australia
[2] Monash Univ, Sch Phys, Clayton, Vic 3800, Australia
[3] Iowa State Univ, Ames Lab, Ames, IA 50011 USA
[4] Iowa State Univ, Dept Phys & Astron, Ames, IA 50011 USA
[5] Univ Glasgow, Dept Chem, Glasgow G12 8QQ, Lanark, Scotland
关键词
density functional calculations; electrochemistry; EPR spectroscopy; molybdenum; polyoxometalates; sulfite;
D O I
10.1002/chem.200501450
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The synthesis, isolation and structural characterization of the sulfite polyoxomolybdate clusters alpha-(D-3h)-(C20H44N)(4){alpha-[Mo18O54(SO3)(2)]}(CH3CN)-C-. and beta-(D-3d)(C20H44N)(4){beta-[Mo18O54-(SO3)(2)]}.CH3CN is presented. Voltammetric studies in acetonitrile (0.1 m Hx(4)NClO(4), Hx(4)N=tetra-n-hexylammonium) reveal the presence of an extensive series of six one-electron reduction processes for both isomers. Under conditions of bulk electrolysis, the initial [Mo18O54(SO3)(2)](4--/5-) and [Mo18O54(SO3)(2)](5-/6-) processes produce stable [Mo18O54(SO3)(2)](5-) and [Mo18O54(SO3)(2)](6-) species, respectively, and the same reduced species may be produced by photochemical reduction. Spectroelectrochemical data imply that retention of structural form results upon reduction, so that both alpha and beta isomers are available at each of the 4-, 5-, and 6-redox levels. However, the alpha isomer is the thermodynamically favored species in both the one- and two-electron-reduced states, with beta ->alpha isomerization being detected in both cases on long time scales (days). EPR spectra also imply that increasing localization of the impaired electron occurs over the alpha-and beta-[Mo18O54(SO3)(2)](5-) frameworks as the temperature approaches 2 K where the EPR spectra show orthorhombic symmetry with different g and hyperfine values for the alpha and beta isomers. Theoretical studies support the observation that it is easier to reduce the a cluster than the beta form and also provide insight into the driving force for beta ->alpha isomerization in the reduced state. Data are compared with that obtained for the well studied alpha-[Mo18O54(SO4)(2))](4-) sulfate cluster.
引用
收藏
页码:8472 / 8483
页数:12
相关论文
共 69 条
[1]   Direct electrochemistry of a bacterial sulfite dehydrogenase [J].
Aguey-Zinsou, KF ;
Bernhardt, PV ;
Kappler, U ;
McEwan, AG .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 2003, 125 (02) :530-535
[2]  
[Anonymous], 1999, J APPL CRYSTALLOGR, V32, P837
[3]  
[Anonymous], ANGEW CHEM
[4]   Pulsed EPR studies of nonexchangeable protons near the Mo(V) center of sulfite oxidase:: Direct detection of the α-proton of the coordinated cysteinyl residue and structural implications for the active site [J].
Astashkin, AV ;
Raitsimring, AM ;
Feng, CJ ;
Johnson, JL ;
Rajagopalan, KV ;
Enemark, JH .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 2002, 124 (21) :6109-6118
[5]   STABILIZATION AND MAGNETIC-RESONANCE CHARACTERIZATION OF THE ONE-ELECTRON HETEROPOLY BLUE DERIVATIVE OF THE MOLYBDOPHOSPHATE [P2MO18O62](6-) - SLOW INTRAMOLECULAR PROTON-EXCHANGE OF THE 2-ELECTRON BLUE IN ACETONITRILE SOLUTION [J].
BARROWS, JN ;
POPE, MT .
INORGANICA CHIMICA ACTA, 1993, 213 (1-2) :91-98
[6]  
Bond A. M, 2002, Broadening ElectrochemicalHorizons: Principles and Illustration of Voltammetric and RelatedTechniques, DOI DOI 10.1021/cm021045x
[7]  
BOND AM, 2004, TRENDS MOL ELECTROCH, pCH14
[8]   A REINVESTIGATION OF ISOMERISM IN THE DAWSON STRUCTURE - SYNTHESES AND W-183 NMR STRUCTURAL CHARACTERIZATION OF 3 NEW POLYOXOTUNGSTATES [X2W18O62]6- (X=P-V, AS-V) [J].
CONTANT, R ;
THOUVENOT, R .
INORGANICA CHIMICA ACTA, 1993, 212 (1-2) :41-50
[9]   THE STRUCTURE OF THE 9(18)-HETEROPOLY ANION IN POTASSIUM 9(18)-TUNGSTOPHOSPHATE, K6(P2W18O62).14H2O [J].
DAWSON, B .
ACTA CRYSTALLOGRAPHICA, 1953, 6 (02) :113-126
[10]   Electron delocalization and magnetic state of doubly-reduced polyoxometalates [J].
Duclusaud, H ;
Borshch, SA .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 2001, 123 (12) :2825-2829