Self-Assembly and Structure of Cobalt(II) Complexes Using Diaminodiamide Ligands

The self-assembly of Co(II) with two diaminodiamide ligands, 4,7-diazadecanediamide and 4,8-diazaundecanediamide, gave two different crystals, [(C8H18N4O2)Co(OH)(2)CO(C8H18N4O2)]Cl-2 (1) [Co(C9H(20)N(4)O(2))(Cl)(H2O)]center dot Cl center dot 2H(2)O (2). Structures of 1 and 2 were characterized by single-crystal X-ray diffraction analysis. Structural data for 1 shows a novel type of binuclear complex with distorted octahederal coordination geometry around the Co atoms through the hydroxo bridges. By using inter-connector N-H center dot center dot center dot N hydrogen bonding interactions as building forces, each cationic moiety [(C8H18N4O2)Co(OH)(2)CO(C8H18N4O2)](2+) is linked to neighboring ones, producing a charged hydrogen-bonded I D chain-like structure. The chains are further connected into a 2D layer in a (4,4)-topology via N-H center dot center dot center dot Cl-free hydrogen-bonding interactions. Structural data for 2 indicate that the cobalt atom adopts a six-coordinated N2O4 environment, giving a distorted octahedral geometry, where two N- and two O-donor sets of ligand located at equatorial positions and one water and one chloride occupied at axial positions. Through NH center dot center dot center dot Cl-Co and OH center dot center dot center dot Cl-Co contacts, each cationic moiety [Co(C9H20N4O2)(Cl)(H2O)](+) in 2 is linked to neighboring ones, producing a charged hydrogen-bonded 1D chainlike structure. Thus, the crystal-engineering approach has proved successful in the solid-state packing due to steric strain effect of the diaminodiamide ligand.