1D and 3D arrays of isomeric cadmium(II) diphosphonates constructed from N,N-dimethylaminomethane-1,1-diphosphonate ligand

Two isomeric cadmium(II) diphosphonates built up from corner-sharing CdO6 octahedra and CPO3 tetrahedra, with the same formula of [Cd(H3L)2] (H4L = (CH3)2N–CH(PO3H2)2), have been synthesized and structurally characterized. Compound 1 shows a 1D chain structure in which the adjacent Cd2+ ions are doubly bridged by two equivalent H3L− anions, whereas compound 2 exhibits a novel non-centrosymmetric 3D framework which is formed by a pillared-layer array, with one type of H3L− anions participating in the construction of a 21-symmetry layer and the other type of H3L− anions acting as pillars.