Small non-polar complexes exhibiting significant piezoelectric properties: Solvothermal synthesis and crystal structures of MO5V(tren)·H2O (M=Mo and W; tren=tris(2-aminoethyl)amine)

The two isostructural complexes MO5V(tren)·H2O (M=Mo (1) and W (2)) were synthesized under solvothermal conditions at pH≈12 crystallizing in the non-centrosymmetric space group P212121. The structures are constructed by a distorted tetrahedral [MO4]2− anion bound via one shared oxygen atom to a severely distorted [VIVN4O]2+ complex completing the octahedral coordination around the V centre. The two O atoms in the VN4O2 octahedron are in cis position. The two compounds represent rare examples where the [MO4]2− anion is acting as a ligand. Both compounds exhibit a piezoelectric effect which is more pronounced for M=Mo. The samples are further characterized with IR and UV/Vis spectroscopy and thermal analysis.