Metal- and ligand-dependent topologies and chirality in luminescent cadmium and zinc trans-aconitate coordination polymers with bis(pyridylmethyl)piperazine ligands

Abstract

Zinc and cadmium coordination polymers containing both trans-aconitate (acon) and bis(pyridylmethyl)piperazine (bpmp) ligands show dramatically different dimensionalities and topologies depending on metal coordination environment and nitrogen donor atom disposition. {Zn(acon)(H4-bpmp)·9.5H2O}n (1) displays a chiral threefold interpenetrated diamondoid lattice along with “infinite” water molecule slabs. {[Cd(H2O)(acon)(H4-bpmp)]·3H2O}n (2) manifests a very rare 4-connected chiral layered net with 658 topology, formed by offset covalent linkage of anionic [Cd(H2O)(acon)]nn− chain motifs by long-spanning H4-bpmp+ tethers. Use of an isomeric bis(pyridylmethyl)piperazine ligand with a kinked nitrogen donor disposition resulted in the achiral 1D coordination polymer solid {[Cd(acon)(H3-bpmp)]·3H2O}n (3), which possesses a supramolecular 3D 3,8-connected binodal network with (4.62)4(41264812) topology. Ultraviolet irradiation of 1–3 resulted in blue-violet light emission from molecular orbital transitions within the bpmp ligands.