Ionothermal syntheses of three transition-metal-containing polyoxotungstate hybrids exhibiting the photocatalytic and electrocatalytic properties

Employing the ionothermal synthesis approach, three new transition-metal-containing polyoxotungstate hybrids: [Dmim](2)Na-3[SiW11O39Fe(H2O)] center dot H2O (Dmim=1,3-Dimethylimidazole) (1), [Emim](9)Na-8 [(SiW9O34)(3){Fe-3(mu(2)-OH)(2)(mu(4)-O)}(3)(WO4)] center dot 0.5H(2)O(Emim=1-Ethyl-3-meth-ylimidazole) (2) and [Dmim] 2[HMim]Na-6[(AsW9O33)(2){Mn-III(H2O)}(3)] center dot 3H(2)O (Dmim=1,3-Dimethylimidazole; Mim=1-Methylimidazole) (3) have been synthesized in 1-ethyl-3-methyl imidazolium bromide ([Emim]Br) ionic liquids (ILs). Compound 1 possesses a 3-D open framework constructed from the mono-iron(III)-substituted alpha-Keggin-type anion and the organic cations [Dmim]+ through the hydrogen bond interactions. Compound 2 contains a [{Fe-3(III)(mu(2)-OH)(2)(mu(3)-O)}(3)(mu(4)-WO4)] cluster surrounded by three [SiW9O34](10-) ligands, eight sodium cations and nine dissociative [Emim](+) cations around the polyoxoanion. The polyoxoanion of 3 consists of a high-valent trinuclear-manganese (III)-substituted sandwiching polyoxoanion based on the [alpha-AsW9O33](9-) units. All the compounds are characterized by elemental analyses, IR, UV-vis spectra, TG-DTA and XRD analyses. The XPS and EPR spectra of Mn-III in 3 were studied, The photocatalytic and electrocatalytic properties, as well as the stabilities of 1-3 were also investigated. (C) 2009 Elsevier Inc. All rights reserved.