Preparation of open and closed forms of the lvt network with Cu(ii) complexes of structurally related 1,2-diazole ligands

Abstract

Reported here are the synthesis and structural characterisation of two topologically related coordination polymers: [Cu(L1)(CH₃CONH₂)], 1, and [Cu(L2)(NMP)]·0.5NMP·0.5H₂O, 2, (NMP = N-methyl-pyrrolidinone) prepared from 1H-indazole-3-carboxylic acid, H₂L1, and 1H-pyrazole-3-carboxylic acid, H₂L2, respectively. Both 1 and 2 crystallise in the tetragonal space group I4₁/a and form 3-dimensional coordination polymers described by the lvt topology, in which [Cu₂L₂] dimers form four-connected nodes linked through carboxylate groups. Within 1 the presence of a Cu-bound acetamide molecule (formed in situ by the solvothermal hydration of acetonitrile) propagates hydrogen bonding between dimer units that, combined with the steric bulk of the indazole fragment, yield a closed (non-porous) framework. In 2, however, Cu-bound NMP, which does not participate in hydrogen bonding, coupled with the less bulky nature of the pyrazole-backbone, gives rise to an open framework of an otherwise isostructural network.