Infrared and Polarized Raman Spectra of M6[TeMo6O24] · 7H2O[M = K, NH4] and (NH4)6[TeMo6O24] · Te(OH)6 · 7H2O Single Crystals

Abstract

Heteropolymolybdates are widely used as industrial catalysts, ion exchange agents, corrosion inhibitors, and solid state electrolytes for fuel cells. The infrared (IR) and polarized Raman spectra of K6[TeMo6O24] · 7H2O, (NH4)6[TeMo6O24] · 7H2O, and (NH4)6[TeMo6O24] · Te(OH)6 · 7H2O single crystals have been recorded and analyzed. The Te-O vibrations and the bridging and terminal Mo-O vibrations observed in the IR and Raman spectra confirm a finite [TeMo6O24]6- heteropolyanion in all the three crystals. TeO6 octahedra are considerably distorted in NTMH1 and NTMH2 crystals, while the distortion is less in KTMH. The NH+4 ion does not rotate freely in the crystalline lattice and the N-H · · · O bonds form an asymmetric potential in both ammonium-containing crystals. Stretching and bending vibrations of water molecules show hydrogen bonds of various strengths in all three crystals. Two crystallographically distinct water molecules are identified in KTMH crystal.