Capture of aromatic carboxylate anion through second sphere coordination:: Topological complementarity of [cis-Co(en)2(N3)2]+ and C7H3ClNO4- ions

[cis-Co(en)(2)(N-3)(2)]C(7)H(3)ClNO4 center dot 1.25H(2)O (Cocnb) was synthesised and detailed packing analyses were undertaken to delineate the topological complementarity of [cis-Co(en)(2)(N-3)(2)](+) and a 2-chloro-4-nitro benzoate anion (cnb) for second sphere coordination in the crystal lattice. The complex was completely characterised by elemental analyses, spectroscopic studies (IR, UV/visible, H-1 and C-13 NMR). The compound crystallizes in the monoclinic (space group C2/c) with a = 21.9843(18), b = 8.7959(7), c = 23.0121(18) angstrom. beta = 116.426(1)degrees, V = 3984.9(6) angstrom(3), and Z = 8. In the crystal lattice, discrete ions of [cis-Co(en)(2)(N-3)(2)](+) and cnb are arranged in ...A-B-A-B... pattern (in both a and c directions of the lattice) forming columns of anions and cations. The anionic columns are pi stacked and are involved in extensive hydrogen bonding interaction. It appears that the topological feature of [cis-Co(en)(2)(N-3)(2)](+) is conducive for generating second sphere interactions with aromatic carboxylates. This strategy may be used as a viable method for the capture of aromatic carboxylate anions. (C) 2007 Elsevier B.V. All rights reserved.