Low temperature molten salt synthesis of noncentrosymmetric (NH4)(3)SbF3(NO3)(3) and centrosymmetric (NH4)(3)SbF4(NO3)(2)

Two fluorine antimony nitrates named (NH4)(3)SbF3(NO3)(3) and (NH4)(3)SbF4(NO3)(2) have been successfully synthesized by a low temperature molten salt method. Although these two title compounds possess NO3- groups and similar Sb-polyhedra, they exhibit completely different macroscopic centricities, (NH4)(3)SbF3(NO3)(3) being noncentrosymmetric while (NH4)(3)SbF4(NO3)(2) being centrosymmetric, which is induced by the discrepant coordination environments of Sb3+. Interestingly, the noncentrosymmetric (NH4)(3)SbF3(NO3)(3) exhibits a strong second harmonic generation response (3.3 x KDP), a large birefringence (0.098@546 nm) and a large band gap (3.77 eV), indicating its potential as a UV nonlinear optical material. Detailed structure-property analysis confirms that the superior optical property is due to the synergistic effect of the planar pi-conjugated NO3- groups and the stereochemically active lone pair containing Sb3+ cations.