Two M(II)-diphosphonate coordination polymers: structural, fluorescent and magnetic studies (M = Cu,Ca)

Two examples of CuII/CaII-diphosphonate coordination polymers, [Cu2(L)(H2O)2]n 1 and {[Ca(L-H2)]2·2H2O}n 2 (H4L = H2O3PCH2N(C4H8)NCH2PO3H2), L-H2 = O3PCH2HN(C4H8)NHCH2PO3), N,N′-piperazinebis(methylenephosphonic acid)), have been hydrothermally synthesized and characterized by elemental analysis, FT-IR, PXRD, TGA and single-crystal X-ray diffractions. Compound 1 possesses a 2-D inorganic-organic alternate arrangement layer structure, in which ligand H4L shows a never reported multi-dentate coordination mode. Compound 2 possesses a 3-D open-framework structure with 1-D channel built from 44-atom rings. Results of fluorescent measurements indicate the maximum emission band centered at 435 nm of 1 should be due to the coordination effect with metal(II) ions, and the high energy emission peaks (383, 298 nm for 1 and 378, 300 nm for 2) could be derived from the intraligand π*→n transition station of H4L (382, 310 nm, λex = 235 nm). Magnetism analysis of 1 indicated antiferromagnetic interactions being from the 1-D magnetic chain with the binuclear unit [Cu2O2].