Synthesis, characterization and X-ray crystallographic investigation of 2-D hybrid hydrogen bonded and rectangular grid networks in Cu(II) and Co(II) metal complexes

Two copper/cobalt metal complexes, [Cu(L-cys)(2,2'-bpy)(H2O)] (1) and {[Co(L-cys)(4,4'-bpy)(H2O)center dot H2O}(n) (2), with the N-donor ligands 2,2'-bipyridyl/4,4'-bipyridyl and the L-cysteate dianion (L-cys) have been synthesized by different reaction methods and structurally characterized. Compound 1 exists as a discrete monomeric unit in which the metal ions possess a distorted square-pyramidal coordination environment provided by nitrogen atoms from the 2,2'-bpy ligand and the amino-carboxylate group of L-cys in a chelated coordination, constituting the square base, and with a water molecule occupying the axial coordination site to complete the penta coordination. Packing and hydrogen bonding interactions of 1 reveal that the screw related monomeric units are involved in intermolecular hydrogen bonding with the formation of helical bilayers via O-H center dot center dot center dot O and N-H center dot center dot center dot O interactions. These hydrogen bonded bilayered helical nets are involved in stacking and C-H center dot center dot center dot O interactions which generate a two dimensional hydrogen bonded network in the bc-plane. Complex 2 is a two dimensional coordination polymer which is insoluble in common polar and non-polar solvents. The coordination around the metal center possesses a distorted octahedral geometry. The adjacent metal centers are bridged via the carboxylate group of the L-cys moiety in a syn-anti fashion, generating a one dimensional helical network along the b-axis. Adjacent helical chains are further pillared by the 4,4'-bpy ligand through the terminal nitrogen atoms, generating a two dimensional square grid type coordination network. Both the complexes are characterized well by various physico-chemical techniques such as CHN analysis, IR spectroscopy, PXRD and CD analysis. (C) 2010 Elsevier Ltd. All rights reserved.