Counteranion and donor disposition effects on the topology of luminescent cadmium coordination polymers incorporating bis(pyridylmethyl)piperazine isomers

Four divalent cadmium coordination polymers, incorporating isomers of the hydrogen bonding capable diimine bis(pyridylmethyl)piperazine, have been prepared via solvent diffusion methods. Single crystal X-ray diffraction studies revealed both nitrogen donor disposition and anion dependence on dimensionality and topology. {[Cd(H2O)4(4-bpmp)](ClO4)2 · (4-bpmp) · 4H2O}n (1, 4-bpmp = bis(4-pyridylmethyl)piperazine) exhibits cationic 1-D [Cd(H2O)4(4-bpmp)]n2n+ chains that aggregate via extensive hydrogen bonding. {[Cd(3-bpmp)3(H2O)2](ClO4)2·5H2O}n (2, 3-bpmp = bis(3-pyridylmethyl)piperazine) manifests 1-D coordination polymer chains with curled, pendant monodentate 3-bpmp ligands. {[Cd(H2O)4(4-bpmp)]2[Cd(H2O)3(SO4)(4-bpmp)][Cd(H2O)2(SO4)2(4-bpmp)]·10H2O}n (3) displays sets of cationic [Cd(H2O)4(4-bpmp)]n2n+ chains, neutral [Cd(H2O)3(SO4)(4-bpmp)]n   chains and anionic [Cd(H2O)2(SO4)2(4-bpmp)]n2n- chains linked into a pseudo 3-D lattice via numerous hydrogen bonding interactions. {CdSO4(H2O)3(3-bpmp)0.5]n (4) possesses a 2-D layered structure in which cadmium ions are connected by bridging 3-bpmp tethers and ligated sulfate ions. All four coordination polymers undergo blue–violet luminescence upon exposure to ultraviolet light.