Designing anisotropic cyanometallate coordination polymers with unidirectional thermal expansion (TE): 2D zero and 1D colossal positive TE.

Oxidative addition of halogens to tetracyanoplatinate results in the formation of a Pt(iv)-building block that, combined with Cu(ii), forms coordination polymers Cu(H2O)2[PtX2(CN)4] (X = Br, Cl). These materials exhibit directional anisotropic thermal expansion: nearly zero expansion within the cyanometallate sheets and positive thermal expansion in the third dimension.