Carboxylate-bridged helical-chain Cu(II) complex and zig-zag chain Ni(II) and Co(II) complexes from 8-quinolinyloxyacetate

Tridentate carboxylate-containing ligand L (L=8-quinolinyloxyacetate) reacts with M(II) chloride (M=Cu, Ni and Co) to give rise to three coordination polymers [CuLCl]n (1), {[NiL(H2O)2]Cl·H2O}n (2), and {[CoL(H2O)2]Cl·H2O}n (3), respectively. Complex 1 is a helix chain polymer while 2 and 3 are two zig-zag chain polymers. The bridging carboxylate groups are in anti-anti bridging mode in complex 1 while they are within syn-anti conformation in 2 and 3. In 1, carboxylate groups link two basal positions in basal-apical, while in complexes 2 and 3, they are basal-basal positions. The structures of these complexes have been determined by X-ray crystallography. Interestingly, three chain complexes are also linked to form 3D networks through hydrogen bonds.