Syntheses, structural characterization and electrochemical properties of two rare-earth–isonicotinic-acid containing silicomolybdates

Abstract

Two rare-earth–isonicotinic-acid containing silicomolybdates [NH4]6[RE(INA)2(HINA)(H2O)3]2[α-SiMo12O40]2·6H2O [RE=NdIII (1), ErIII (2); HINA=isonicotinic acid] have been synthesized in the conventional aqueous solution and characterized by elemental analyses, IR spectra, UV spectra and single-crystal X-ray diffraction. Both 1 and 2 crystallize in the triclinic P–1 space group and consist of two typical Keggin [α-SiMo12O40]4− polyanions, one isolated rare-earth-isonicotinic-acid [RE(INA)2(HINA)(H2O)3]22+ dimeric complex cation, six NH4+ ions and six lattice water molecules. Interestingly, two rare-earth ions are linked by four INA− ligands in the [Ln(INA)2(HINA)(H2O)3]22+ complex cation, which is very rare in polyoxometalate chemistry. The UV spectral measurements of 1 indicate that 1 is stable in aqueous solution in the pH range of 4.49–9.39. Furthermore, the electrochemical and electrocatalytic properties of 1 have been measured by cyclic voltammetry in 0.5mol·L−1 Na2SO4+H2SO4 aqueous solution at the scan rate of 100mV·s−1.