New metal phosphonates containing coordination piperazine or pyridyl groups

Reactions of transition metal(II) salts with three aminophosphonic acids, 1-[(H2O3PCH2)2NCH2CH2−]-piperazine-4-CH2PO3H2 (H6L1), 3-pyridyl-CH2N(CH2PO3H2)2 (H4L2) and 4-pyridyl-CH2N(CH2PO3H2)2 (H4L3) afforded three new metal phosphonates, namely, Cu(H4L1)·2H2O (1), Co(H3L2)2·H2O (2) and [Co(H2L3)(H2O)]·H2O (3). The structure of compound 1 features a 1D chain in which the CuN2O3 and CPO3 polyhedra are interconnected by bridging phosphonate ligands to form 1D chains. Compound 2 has a layered structure. The cobalt(II) ions in the octahedral coordination geometries and {CPO3} tetrahedra are interconnected into an inorganic chain via –N(CH2PO3H)2 moieties, and adjacent chains are further bridged by the coordination pyridyl groups of H3L2 into a 2D layer. The structure of compound 3 features a 2D double layered structure, in which the Co(II) ions are interconnected by bridging phosphonate groups into a 1D chain along b-axis. Neighboring chains are interconnected by coordination pyridyl groups into a double layer perpendicular to the c-axis.