1D and 3D coordination polymers with the M(μ1,μ1-X)2M motif (M = Na, Zn, Cd): Observation of a linear [formula omitted] cation and a five-connected sqp-net

Abstract

Three polymeric complexes [Zn(pydz)(N3)(SO4)]n[Na(H2O)4]n(H2O)4n (1), [Cd(3-ampy)(N3)Cl]n (2), and [Cd(DENA)Cl2(H2O)]n (3), (pydz=pyridazine or 1,2-diazine, 3-ampy=3-aminopyridine, DENA=N,N-diethylnicotineamide) have been synthesized and characterized by spectral and structural methods and their network topologies analysed. Complex 1 crystallizes in monoclinic C-centred space group C2/m, the Zn(1) center is octahedrally coordinated; and simultaneously bridged by EO-azido, N,N′-pydz, and O,O′-sulphato ligands. The ZnN4O2-octahedra form a 1D anionic chain along b-axis. The Na(OH2)6-octahedra have also common water molecules, thus also forming a 1D chain along b-axis. The cationic and anionic chains are connected via hydrogen bonds of type O–H⋯O including lattice water molecules to form a supramolecular 3D network structure. In complex 2, the Cd(1) is six-coordinated by two EE-bridging azide groups, and two nitrogen atoms of bridging N,N′, 3-ampy ligand, and two bridging chloro ligands. The three different bridging ligands connect the distorted octahedra of the Cd(II) centres to form a 3D network structure with the topology of a square pyramidal net (43·66-sqp). The centrosymmetric Cd2Cl2-rings are planar and the NH2- of the 3-ampy groups forms additional hydrogen bonds of type N–H⋯N to the adjacent azido groups. In complex 3, the octahedrally coordinated Cd(1) centres are occupied by alternating monodentate DENA ligand and a water molecule and the other four sites are occupied by four bridging chloro ligands. Thus the Cd2Cl2-rings form common edges to form 1D chains of Cd(II) octahedra along the b-axis of the monoclinic unit cell. 2D supramolecular sheets extended along the bc-planes of the unit cell are formed by the O–H⋯O hydrogen bond. The IR spectra of the three complexes were measured and they confirm the X-ray structural data.