Molecular assemblies based on the template-directing effect of anionic polyoxometalate clusters and organic cationic flexibility

Molecular assembly processes by utilizing the template-directing effect of anionic polyoxometalate clusters and the flexible organic cation have achieved three hybrids: (H(2)bpp)(Hbpp)[PMo12O40]center dot 3DMF (1), (H(2)bpp)(Hbpp)(bpp)(2) [PMo9V3O40(VO)(2)](2) (2), and (H(2)bPP)(2)[beta-Mo8O26] (3) (bpp = 1,3-bis(4-pyridyl)propane). Three compounds were characterized using single crystal X-ray crystallography, elemental analysis, IR, XPS. EPR. voltammetric behavior and TGA. Crystal structural analyses revealed that compounds 1-3 were all constructed from protonated organic bpp cations with different POM clusters: isolated alpha-Keggin P-Mo cluster in 1; dimer of bi-capped alpha-Keggin P-Mo-V anions linked through a (V2O2) unit in 2: beta-octamolybdate isopolyanion in 3, respectively. All three assemblies demonstrated a higher thermal stability. The protonated bpp cations lost at temperature higher than 300 degrees C that the strong intermolecular interactions may account for the high initial temperature of weight loss. The electrochemistry property of compound 2 modified carbon paste electrode was also studied in 1 M H2SO4 aqueous. (C) 2009 Elsevier Ltd. All rights reserved.