Syntheses, Crystal Structures, and Properties of Five New Transition Metal Molybdenum(VI) Selenites and Tellurites

Five new transition metal molybdenum(VI) selenites or tellurites, namely, TM(MoO3)(SeO3)(H2O) (TM = Mn, Co), Fe2(Mo2O7)(SeO3)2(H2O), Cu2(MoO4)(SeO3), and Ni3(MoO4)(TeO3)2, have been prepared and structurally characterized. They belong to five different types of structures. Mn(MoO3)(SeO3)(H2O) and Ni3(MoO4)(TeO3)2 are non-centrosymmetric and crystallize in the orthorhombic space groups Pmc21 and P212121, respectively, whereas Co(MoO3)(SeO3)(H2O), Fe2(Mo2O7)(SeO3)2(H2O), and Cu2(MoO4)(SeO3) are centrosymmetric and crystallize in P1̅, C2/c, P21/c, respectively. The Mo6+ cations in Mn(MoO3)(SeO3)(H2O), Co(MoO3)(SeO3)(H2O), and Fe2(Mo2O7)(SeO3)2(H2O) are in severely distorted octahedral geometry whereas those in Cu2(MoO4)(SeO3) and Ni3(MoO4)(TeO3)2 are in a slightly distorted tetrahedral geometry. Second-Harmonic Generation (SHG) measurements revealed that (MoO3)(SeO3)(H2O) displays a moderate SHG signal of about 3 × KH2PO4 (KDP) whereas the SHG response of Ni3(MoO4)(TeO3)2 is much weaker than that of KDP.