A three-dimensional pyrazine-2,5-dicarboxylate Cd(II) coordination framework with new (4,4,4)-connected three-nodal topology.

Poly[(mu(4)-pyrazine-2,5-dicarboxylato)cadmium(II)], [Cd(C(6)H(2)N(2)O(4))](n) or [Cd(pzdc)](n) (pzdc is the pyrazine-2,5-dicarboxylate dianion), has been synthesized hydrothermally. The asymmetric unit consists of a Cd(II) atom and two independent halves of pzdc ligands that can be expanded via inversion through the centres of the ligands so that each ligand binds to four Cd(II) atoms with the same binding mode using six donor atoms. The Cd(II) centre is in a distorted octahedral coordination geometry with four O- and two N-atom donors from four pzdc ligands. The infinite linkage of the metal atoms and ligands forms a three-dimensional framework with a rectangular channel which is so narrow that there is no measurable void space in the overall structure. This coordination polymer represents the first example of (4,4,4)-connected three-nodal framework.