Preparation and characterization of two new Cu II supramolecular coordination polymers incorporating sulfobenzoate and flexible heterocyclic ligands

The assembly of Cu II with the multifunctional ligand 2‐amino‐4‐sulfobenzoic acid (H 2 asba) in the presence of the auxiliary flexible ligands 1,4‐bis(triazol‐1‐ylmethyl)benzene (bbtz) and 1,4‐bis(imidazol‐1‐ylmethyl)benzene (bix) under ambient conditions resulted in two new supramolecular coordination polymers, namely poly[[(3‐amino‐4‐carboxybenzenesulfonato‐κ O )aquabis[μ 2 ‐1,4‐bis(triazol‐1‐ylmethyl)benzene‐κ 2 N 4 : N 4′ ]copper(II)] 3‐amino‐4‐carboxybenzenesulfonate tetrahydrate], {[Cu(C 7 H 6 NO 5 S)(C 12 H 12 N 6 ) 2 (H 2 O)](C 7 H 6 NO 5 S)·4H 2 O} n , ( 1 ), and poly[[bis(μ 2 ‐2‐amino‐4‐sulfonatobenzoato‐κ 3 O 1 : N , O 1′ )tetraaqua[μ 2 ‐1,4‐bis(triazol‐1‐ylmethyl)benzene‐κ 2 N 4 : N 4′ ]dicopper(II)] tetrahydrate], {[Cu 2 (C 7 H 5 NO 5 S) 2 (C 14 H 14 N 4 )(H 2 O) 4 ]·4H 2 O} n , ( 2 ). Single‐crystal X‐ray structure diffraction analysis of ( 1 ) reveals that the bbtz ligand acts as a bridge, linking adjacent Cu II ions into a two‐dimensional cationic (4,4) topological network, in which the coordinated 3‐amino‐4‐carboxybenzenesulfonate (Hasba − ) anion uses its sulfonate group to bind with the Cu II ion in a monodentate fashion and the carboxylate group remains protonated. The lattice Hasba − anion resides in the two‐dimensional layer and balances the charge. The carboxylate group of the 2‐amino‐4‐sulfonatobenzoate (asba 2− ) ligand in ( 2 ) is involved in bidentate coordination, connecting adjacent Cu II ions into carboxylate‐bridged chains which are further bridged by the auxiliary flexible bix ligand in a trans – gauche (TG) mode, resulting in the formation of a two‐dimensional network architecture. The amino group of the asba 2− ligand in ( 2 ) also takes part in the coordination with the central Cu II ion. The six‐coordinated Cu II centres in ( 1 ) and ( 2 ) exhibit distorted octahedral coordination geometries. Extensive hydrogen bonding exists in both ( 1 ) and ( 2 ). The interlayer hydrogen bonds in both compounds further extend adjacent two‐dimensional layers into three‐dimensional supramolecular network architectures. Furthermore, a detailed analysis of the solid‐state UV–Vis–NIR (NIR is near IR) diffuse reflectance data indicates that ( 1 ) and ( 2 ) may have potential as wide band gap indirect semiconductor materials. Compounds ( 1 ) and ( 2 ) show reversible and irreversible dehydration–rehydration behaviours, respectively.