Second sphere coordination in anion binding: Synthesis, characterization and single crystal X-ray structure determination of tris(1,10-phenanthroline)cobalt(III) chloride dimesitylenesulphonate undecahydrate, [Co(phen)3]Cl[(CH3)3C6H2SO3]2·11H2O

Orange coloured single crystals of [Co(phen)3]Cl[(CH3)3C6H2SO3]2·11H2O were obtained, when the solution obtained by mixing separately dissolved, tris(1,10-phenanthroline)cobalt(III)chloride and sodium salt of mesitylenesulphonic acid in aqueous medium in 1:3 molar ratio was allowed to evaporate slowly at room temperature. The newly synthesized complex salt was characterized by elemental analyses, TGA, spectroscopic studies (IR, UV/Visible, 1H, 13C and 59Co NMR), conductance and solubility product measurements. Single crystal X-ray structure determination of [Co(phen)3]Cl[(CH3)3C6H2SO3]2·11H2O revealed that complex salt crystallizes in the monoclinic crystal system with space group P21/c where a = 17.7628(4), b = 15.7546(3), c = 20.8338(5)Å, β = 104.691(1), V = 5639.65 Å3, Z = 4. The asymmetric unit consists of one cation, one chloride, two mesitylenesulphonate ions and eleven lattice water molecules. Crystal lattice is stabilized by hydrogen bonding interactions of type CH⋯O, CH⋯Cl through second sphere coordination and OH⋯O interactions besides the electrostatic forces of attractions. The solubility product measurements indicated that the affinity of cationic metal complex tris(1,10-phenanthroline)cobalt(III), [Co(phen)3]3+ is greater for mesitylenesulphonate ion than for chloride ion in aqueous medium. The structural studies suggest that [Co(phen)3]3+ is a potential anion receptor for the mesitylenesulphonate ion. This is the first crystal structure report of [Co(phen)3]3+ complex cation with any arylsulphonate ion.