Syntheses, structures, network topologies and photoluminescence of four Zn(II) and Cd(II) coordination polymers based on 5-carboxyl-1-carboxymethyl-2-oxidopyridinium

5-Carboxyl-1-carboxymethyl-2-oxidopyridinium (H2CCOP) and a combination of N-donor ligands, such as 4,4′-bipyridine (4,4′-bipy) and 1,10-phenanthroline (phen) with d10 metal ions Zn(II) and Cd(II) give rise to four coordination polymers, namely, [Zn2(CCOP)(OH)2(H2O)] (1), [Zn(CCOP)(phen)(H2O)]·H2O (2), [Cd(CCOP)(H2O)2]·3H2O (3), and [Cd(CCOP)(H2O)] (4) which show different topological structures.