Role of non-covalent interactions in anion binding: Synthesis, characterization and solid state structural studies of [Co(phen)3](SCN)3•2H2O and [Co(phen)2CO3](SCN)•3H2O

In an effort to study role/effect of non-covalent interactions in anion binding, the cobalt(Ill) complex salts, [Co(phen)(3)](SCN)(3)center dot 2H(2)O (1) and [Co(phen)(2)CO3](SCN)center dot 3H(2)O (2) were synthesized by reacting appropriate reactants in aqueous medium and characterized by UV/Visible, IR, NMR, conductance and solubility product measurements. The molecular structure of complex salt 1 and 2 were determined by single crystal Xray crystallography which revealed the presence of discrete ions and lattice water molecules in the solid state. A strong network of hydrogen bond interactions through the weak second sphere interactions (C-H center dot center dot center dot O), strong interactions of type O-H center dot center dot center dot O (water) and pi...pi stacking interaction besides the electrostatic interactions play a very important role in stabilization of crystal lattice. The solubility product measurements, X-ray structure analysis and formation of these salts of definite composition suggest that cationic cobalt(III) complexes, [Co(phen)(3)](3+) and [Co(phen)(2)CO3](+) are promising anion receptors for the thiocyanate ion and presence of hydrogen bond acceptor/hydrogen bond donor groups increase the magnitude of non-covalent (hydrogen bond) interactions. (C) 2009 Elsevier B.V. All rights reserved.