K4TM4(V2O7)2(IO3)4(H2O) (TM = Zn, Ni, Co): a series of quinary mixed metal–vanadium(v)–iodates

Abstract

Systematic explorations of new compounds in the divalent transition metal–vanadium(V)–iodate system by hydrothermal reactions led to three quinary mixed metal iodates, namely, K₄TM₄(V₂O₇)₂(IO₃)₄(H₂O) (TM = Zn, Ni, Co). They represent the first examples of quinary mixed metal vanadium iodates. The structures of K₄TM₄(V₂O₇)₂(IO₃)₄(H₂O) (TM = Zn, Ni, Co) are quite unusual and consist of sandwich-like double layers of ¹_∞[TM₄(V₂O₇)₂(IO₃)₄(H₂O)]⁴⁻ that are separated by K⁺ cations. The interconnection of TMO₆ units via tridentate bridging IO₃⁻ groups resulted in a 2D sheet parallel to the ab-plane. Two such sheets are bridged by V₂O₇ units into a unique sandwich-like double layer. V₂O₇ units are observed in iodates for the first time. Thermal stability and optical properties as well as magnetic properties for the Co and Ni phases were studied.