Reversible adsorption of a planar cyclic (H2O)6 cluster held in a 2D CuII-coordination framework

Synthesis and crystal structure of catena-poly[[hexa-aqua{μ3-2-[bis-(carboxyl-atometh-yl)amino]-terephthalato}dicobalt(II)] penta-hydrate] containing water tapes and penta-mers

The title coordination polymer, {[Co2(C12H7NO8)(H2O)6]·5H2O} n , was crystallized at room temperature from an aqueous solution of 2-aminodi-acetic 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 mol-ecules. Two of the cobalt cations lie on centres of inversion and are coordinated in octa-hedral O2(OH2)4 environments, whereas the other adopts a slightly distorted octa-hedral 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 supra-molecular architecture via networks of hydrogen bonds involving the coordinated and free water mol-ecules. One-dimensional 'water tapes' are formed, containing alternating six-membered and twelve-membered rings of water mol-ecules, together with water penta-mers, in which a central uncoordinated water mol-ecule is hydrogen bonded to two coordinated and two free water mol-ecules in a tetra-hedral arrangement.