Abstract
A novel bisphosphonate ligand bearing a thiophene group (AleThio) was synthesized and its covalent grafting to polyoxometalates (POMs) investigated. The hybrid polyoxomolybdate [(Mo3O8)(4)(O3PC(O)(C3H6NH2CH2C4H3S)PO3)(4)](8-) [Mo-12(AleThio)(4)] was synthesized in water by the reaction of Na2MoO4 with AleThio. It is built of four {(Mo3O8)-O-VI} units connected by phosphonate groups around a central Na+ ion. The reaction of the trivacant [PW9O34](9-) units with Co-II or Ni-II ions in the presence of AleThio led to the sandwich-type anions [(PW9O34)(2)(OH)(2)(H2O)(4)M-7(O3PC(O)(C3H6NH2CH2C4H3S)PO3)(2)](14-) [M = Ni, Co; M-7(AleThio)(2)]. Salts soluble in organic solvent were prepared by cation-exchange with bis(triphenylphosphine)iminium ions. P-31 NMR spectroscopy showed that Mo-12(AleThio)(4) is stable in acidic medium (pH 4) while the M-7(AleThio)(2) POMs are stable in alkaline medium (6 pH 13). Their cyclovoltammograms were recorded in solution. Attempts to surface immobilize the POMs through homo-polymerization were unsuccessful but co-polymerization employing 3-methylthiophene led to polymeric films with covalently attached POMs.