Synthesis, crystal structures and characterizations of three new layered Zn(II) and Cd(II) aminodiphosphonates

Three new divalent metal(II) aminodiphosphonates with a layered structure have been synthesized by hydrothermal reactions, namely, Zn(H2L1) (1), Cd2(L1) (2) (H4L1=butyl-N(CH2PO3H2)2), and Zn3(HL2)2·1.5H2O (3), (H4L2=cyclo-hexyl-N(CH2PO3H2)2). The 〈100〉 2D zinc(II) phosphonate layer in Zn(H2L1) 1 is built from ZnO4 tetrahedra interconnected by aminodiphosphonate ligands. One phosphonate group of the ligand is tridentate whereas the other one is 1H-protonated and unidentate. The amine group is also protonated. In Cd2(L1) 2, one Cd(II) ion is octahedrally coordinated by one nitrogen atom and five phosphonate oxygen atoms from four L1 anions, whereas the other one is five-coordinated by five phosphonate oxygen atoms in a distorted square pyramidal geometry. The aminodiphosphonate ligand is fully deprotonated, and acts as a undecadentate metal linker. The CdO5N and CdO5 polyhedra are interconnected via edge- and corner-sharing into a 1D chain along b-axis, and such chains are bridged by the diphosphonate ligands into a 〈200〉 metal phosphonate layer. The 〈−101〉 and 〈−202〉 metal phosphonate layers in Zn3(HL2)2·1.5H2O (3) are based on ZnO4 tetrahedra crosslinked by bridging aminodiphosphonate ligands. Both phosphonate groups of the aminodiphosphonate ligand have been deprotonated and are tridentate metal linkers. The amine group remains 1H-protonated. All three compounds exhibit broad emission band in the blue light region.