New organic-inorganic hybrid assemblies based on metal-bis(betaine) coordination complexes and Keggin-type polyoxometalates

The slow diffusion reactions of a double-betaine-containing ligand with YbH[SiMo12O40]center dot nH(2)O and Ca-2[SiMo12O40]center dot nH(2)O led to the isolation of two new organic-inorganic hybrid assemblies, [Yb(O)(HL)(2)(H2L)(0.5)(H2O)(3)][SiMo12O40]center dot 2.5CH(3)CN center dot 1.5H(2)O (1) and Ka(HL)(2)(L)(0.5)(H2O)4] [SiMo12O40]. 5CH(3)CN center dot H2O (2) (L = 1,4-bis(pyridinil-4-carboxylato)-1,4-dimethylbenzene). Compounds 1-2 were characterized by elemental analyses, TG, IR, XPS and single-crystal X-ray diffraction. Compound 1 contains the dinuclear [(YbO)(HL-)(2)(1H(2)O)(3)](2) coordination moieties and discrete protonated L ligands, which are connected together by H-bonds and pi-pi interactions to form a 3D supramolecular framework with the Keggin-type [SiMo12O40](4-) polyoxoanions and solvent molecules encapsulated. Compound 2 possesses discrete [Ca(HL)(2)(L)(0.5)(H2O)(4)](2) co-ordination units that are linked by the extensive intermolecular H-bonds and pi-pi r interactions to form a 3D supramolecular framework with the [SiMo12O40](4-) polyoxoanions and solvent molecules are encapsulated in the interbedded cavities. The structural motifs of the metal-organic coordination units can be obviously modulated by the use of chemically different cationic nodes. The degradation of Rhodamine-B (RhB) under UV irradiation with compounds I and 2 as heterogeneous photocatalysts were investigated, both exhibiting good photocatalytic properties. Furthermore, these hybrid compounds display luminescent properties induced by organic ligands. (C) 2013 Elsevier B.V. All rights reserved.