Anion binding through second sphere coordination: Synthesis, characterization and X-ray structures of cationic carbonato bis(1,10-phenanthroline)cobalt(III) complex with sulphur oxoanions

Abstract

In an effort to utilize the cationic cobalt(III) complex, [carbonato bis(1,10-phenanthroline)cobalt(III)] + as an binding agent (anion receptor) for the sulphur oxoanions ( S 2 O 3 2 - , S 4 O 6 2 - , S 2 O 8 2 - ), three complex salts of composition [Co(phen) 2CO 3] [Co(phen) 2(S 2O 3)]·5·5H 2O ( 1), [Co(phen) 2CO 3] 2S 4O 6·7H 2O ( 2) and [Co(phen) 2CO 3] 2 S 2O 8·4H 2O ( 3) were synthesized and characterized by UV/Visible, IR, NMR and conductance measurements. The molecular structure of complex salts 1– 3 were determined by single crystal X-ray 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···O) and strong interactions of type O–H …O (water) besides the electrostatic interactions play a very important role in stabilizing the crystal lattice. The solubility product measurements, X-ray structure analyses and formation of these salts suggest that cation, [Co(phen) 2CO 3] + present in [Co(phen) 2CO 3]Cl·5H 2O may be used as an anion receptor for the sulphur oxoanions S 2 O 3 2 - , S 4 O 6 2 - and S 2 O 8 2 - ions.