Microheterogeneous mediated electron transfer reaction (ETR) of surfactant cobalt(III) complexes by Fe2+: Effect of pyridine substituent as co ligand

Abstract

The outer sphere electron transfer reaction of surfactant cobalt(III) complexes, Cis-[Co(en)2(4CNP)(C12H25NH2)](ClO4)31, Cis-[Co(trien)(4CNP)(C12H25NH2)](ClO4)32 and Cis-[Co(trien)(4AMP)(C12H25NH2)](ClO4)33 (en: ethylenediamine, trien: triethylenetetramine, 4CNP: 4-cyanopyridine, 4AMP: 4-aminopyridine, C12H25NH2: dodecylamine) have been investigated by Fe2+ ion in liposome vesicles (DPPC) and ionic liquids medium at different temperatures under pseudo first order conditions using an excess of the reductant. In the presence of ionic liquid medium the second order rate constant for this electron transfer reaction was found to increase with increasing concentration of ionic liquids. Below the phase transition temperature of DPPC, the rate decreased with increasing concentration of DPPC, while above the phase transition temperature the rate increased with increasing concentration of DPPC for the same complexes has also been studied. Experimentally the reactions were found to be second order and the electron transfer postulated as outer sphere. The results have been discussed in terms of increased hydrophobic effect, self aggregation and the presence of pyridine ligand containing 4-amino and 4-cyano substituent.