Entangled coordination polymers with mixed N- and O-donor organic linkers: a case of module-matching priority

A series of four coordination polymers showing entangled architectures based on cobalt and mixed N-donor/O-donor ligands, namely [Co(4,4'-BPIPA)(TP)]·2DMF (1), [Co(4,4'-BPIPA)(2,6-NDC)(DMF)]·DMF (2), [Co(4,4'-BPIPA)(2,6-NDC)]·2DMF (3) and [Co(4,4'-BPIPA)(4,4'-BPDC)]·2DMF (4) (4,4'-BPIPA = N,N'-bis-4-pyridinyl-isophthalamide, TP = terephthalic acid, 2,6-NDC = 2,6-naphthalenedicarboxylic acid, 4,4'-BPDC = 4,4'-biphenyldicarboxylic acid), have been synthesized under solvothermal conditions. Complex 1, containing 4,4'-BPIPA and relatively short dicarboxylate ligands (TP), exhibits two-dimensional (2D) two-fold interpenetration of double wavy 4(4)-sql nets. Complex 2 displays interesting 2D→3D parallel polycatenation of undulated 2D 4(4)-sql layers built by 4,4'-BPIPA and moderate dicarboxylate ligands (2,6-NDC). Complexes 3 and 4, although constructed of dicarboxylate ligands with different lengths (moderate 2,6-NDC and long 4,4'-BPDC), possess similar 3-fold interpenetration of identical self-catenated single nets with 6(5)·8-mok topologies. It has been found that the length of the dicarboxylate ligands plays a key role of module-matching in the self-assemblies of complexes 1-4. Moreover, the effect of the conformations of 4,4'-BPIPA, which can be controlled by tuning reaction temperatures, is also discussed.