Second sphere coordination in fluoroanion binding: Synthesis, spectroscopic and X-ray structural study of [Co(phen)2CO3](Pfbz)·6H2O

To explore the anion receptor potential of [Co(phen) 2 (CO) 3 ] + for the pentafluorobenzoate ion, [Co(phen) 2 (CO) 3 ](Pfbz)·6H 2 O (where phen = 1,10-phenanthroline and Pfbz = pentafluorobenzoate) was synthesized by reacting appropriate salts in aqueous medium. A detailed packing analysis has been undertaken to delineate the role of second sphere C–H⋯F interactions amid other heteroatom interactions. The complex salt has been characterized by elemental analyses, spectroscopic studies (IR, UV/Vis, multinuclear NMR) and solubility product measurement. The complex salt crystallizes in the monoclinic crystal system with space group P 2 1 / n having the cell dimensions a  = 13.377(3) A, b  = 17.204(3) A, c  = 15.408(3) A, β  = 108.11(3)°, V  = 3370.1(12) A 3 and Z  = 4. Single crystal X-ray structure determination revealed ionic structure consisting of complex cation, [Co(phen) 2 (CO) 3 ] + , Pfbz anion and six lattice water molecules. In the crystal lattice, discrete ions [Co(phen) 2 CO 3 ] + are forming rectangular voids in which the Pfbz anions are entrapped. Crystal lattice is stabilized by electrostatic forces of attraction and hydrogen bonding interactions, i.e. O–H⋯O, C–H⋯O, and C–H⋯F, involving second sphere coordination besides π⋯π interactions.