Cobalt isothiocyanate coordination polymers constructed from isomeric bis(pyridylmethyl)piperazine ligands: Ribbon and chain motifs and a novel (3,4)-connected supramolecular layer

Slow diffusion conditions have afforded a pair of cobalt isothiocyanate coordination polymers incorporating the flexible and hydrogen-bonding capable organodiimines N,N′-bis(3-pyridylmethyl)piperazine (3-bpmp) and N,N′-bis(4-pyridylmethyl)piperazine (4-bpmp), which were characterized by single-crystal X-ray diffraction and spectral and elemental analysis. While both [Co(NCS)2(3-bpmp)2]n (1) and {[Co(NCS)2(H2O)2(4-bpmp)] · 2H2O}n (2) possess one-dimensional (1-D) coordination polymer units, the donor disposition within the organodiimine promotes significant structural disparities. Compound 1 displays a 1-D double-chain motif, where each cobalt ion is bridged by two exobidentate 3-bpmp ligands. In contrast, compound 2 manifests a single chain pattern, with only one tethering 4-bpmp ligand joining adjacent cobalt ions. Extensive hydrogen-bonding patterns within the structure of 2 results in an intriguing supramolecular 2-D (3,4)-connected layer with (4.62)2(42.62.82) topology. Thermal properties of these materials are also discussed.