Synthesis and crystal structure of catena-poly[[hexaaqua{μ₃-2-[bis(carboxylatomethyl)amino]terephthalato}dicobalt(II)] pentahydrate] containing water tapes and pentamers

Abstract

The title coordination polymer, {[Co2(C12H7NO8)(H2O)6]·5H2O} n , was crystallized at room temperature from an aqueous solution of 2-aminodiacetic terephthalic acid (H4adtp) and cobalt(II) nitrate. The asymmetric unit consists of one adtp4− ligand, one and two half CoII ions, six water ligands coordinated to CoII ions and five uncoordinated water molecules. Two of the cobalt cations lie on centres of inversion and are coordinated in octahedral O2(OH2)4 environments, whereas the other adopts a slightly distorted octahedral NO3(OH2)2 environment. The crystal structure contains parallel stacked, one-dimensional zigzag chains, {[Co2(C12H7NO8)(H2O)6]} n , which assemble into a three-dimensional supramolecular architecture via networks of hydrogen bonds involving the coordinated and free water molecules. One-dimensional `water tapes' are formed, containing alternating six-membered and twelve-membered rings of water molecules, together with water pentamers, in which a central uncoordinated water molecule is hydrogen bonded to two coordinated and two free water molecules in a tetrahedral arrangement.