Three transition metal complexes constructed from a rigid 2,2′-bipyridine-3,3′,6,6′-tetracarboxylic acid ligand: Syntheses, structures and their fluorescence properties

Three complexes, {[Cd(bptcH2)(H2O)]·H2O}n (1), {[Cu(bptc)0.5(H2O)]·H2O}n (2), {[Co2(bptc)(H2O)6]·3H2O}n (3) (bptcH4 = 2,2′-bipyridine-3,3′,6,6′-tetracarboxylic acid) have been synthesized by self-assembly of the rigid bptcH4 ligand and corresponding transition metal salts. The structural analysis indicates that complex 1 displays a two-dimensional (2D) puckered sheet with (44·62) topology built from 4-connecting Cd3N2(OOC)3 cluster and bridging ligand bptcH22−. Complex 2 features a one-dimensional (1D) double-stranded chain made up 4-connecting bptc4− and Cu4N2(OOC)4 cluster. Complex 3 also exhibits a 2D grid with (44·62) topology, similar to that of complex 1. In addition, the fluorescence properties of complexes 1 and 3 have also been explored.