Preparation, crystal structures and magnetic properties of hetero- and homo-metallic coordination polymers with triazacyclononane derivatives bearing propionic acid pendant arms

Abstract

Two Cu(II)–Na(I) hetero-metallic coordination polymers [Cu2Na5(tacntp)2(H2O)9](ClO4)3·2H2O (1) and [Cu2Na5(tacntp)2(H2O)9](ClO4)3·2H2O (2) were constructed from Cu(II) salts and a trisubstituted N-propionic acid functionalized ligand, namely 1,4,7-triazacyclononane-1,4,7-tripropionic acid (tacntpH3). In complex 1, the Na+ ions act as nodes, being surrounded by six [Cu(tacntp)]− moieties resulting in a 2D coordination polymer. In complex 2, Na+ ions are bridged by pendant carboxylate groups and water ligands to give a 1D Na–O inorganic polymeric ribbon, which is expanded into a complicated 2D hetero-metallic array through the connecting [Cu(tacntp)]− units. The differences between the two structures are related to the amount of Na+ ions present in the reaction media. In further experiments, the trisubstituted pro-ligand tacntpH3 underwent a hydrothermal Cu(II)-induced cleavage of one of three pendant arms, and the resultant disubstituted pro-ligand tacndpH2 assembled with Cu(II) to give a 1D homo-metallic zigzag chain compound [Cu(tacndp)]ClO4·H2O (3). Magnetic susceptibility measurements on complex 3 revealed a ferromagnetic interaction between the Cu(II) centers within the 1D chain.