title: Electron-transfer reactions of cobalt(III) complexes. 1. The kinetic investigation of the reduction of various surfactant cobalt(III) complexes by iron(II) in surface active ionic liquids.
abstract: The kinetics of outer sphere electron transfer reaction of surfactant cobalt(III) complex ions, cis-[Co(en)2(C12H25NH2)2](3+) (1), cis-[Co(dp)2(C12H25NH2)2](3+) (2), cis-[Co(trien)(C12H25NH2)2](3+) (3), cis-[Co(bpy)2(C12H25NH2)2](3+) (4) and cis-[Co(phen)2(C12H25NH2)2](3+) (5) (en: ethylenediamine, dp: diaminopropane, trien : triethylenetetramine, bpy: 2,2'-bipyridyl, phen: 1,10-phenanthroline and C12H25NH2 : dodecylamine) have been interrogated by Fe(2+) ion in ionic liquid (1-butyl-3-methylimidazoliumbromide) medium at different temperatures (298, 303, 308, 313, 318 and 323K) by the spectrophotometry method under pseudo first order conditions using an excess of the reductant. Experimentally the reactions were found to be of second order and the electron transfer as outer sphere. The second order rate constant for the electron transfer reaction in ionic liquids was found to increase with increase in the concentration of all these surfactant cobalt(III) complexes. Among these complexes (from en to phen ligand), complex containing the phenanthroline ligand rate is higher compared to other complexes. By assuming the outer sphere mechanism, the results have been explained based on the presence of aggregated structures containing cobalt(III) complexes at the surface of ionic liquids formed by the surfactant cobalt(III) complexes in the reaction medium. The activation parameters (enthalpy of activation ΔH(‡) and entropy of activation ΔS(‡)) of the reaction have been calculated which substantiate the kinetics of the reaction.
authors.affiliation: School of Chemistry, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu, India. Electronic address: naturalnagaraj@gmail.com.
authors.forename: Karuppiah
authors.initials: K
authors.lastname: Nagaraj
authors.affiliation: Post Graduate and Research Department of Chemistry, Vivekananda College, Tiruvedakam West, Madurai 625234, Tamil Nadu, India.
authors.forename: Krishnan
authors.initials: K
authors.lastname: Senthil Murugan
authors.affiliation: Department of Polymer Science, University of Madras, Guindy Campus, Chennai 600 025, Tamil Nadu, India.
authors.forename: Pilavadi
authors.initials: P
authors.lastname: Thangamuniyandi
authors.affiliation: School of Chemistry, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu, India.
authors.forename: Subramanian
authors.initials: S
authors.lastname: Sakthinathan
mesh_terms: D002614:Chelating Agents / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D004579:Electron Transport; D057927:Hydrophobic and Hydrophilic Interactions; D052578:Ionic Liquids / Q000737:chemistry*; D007477:Ions; D007700:Kinetics; D010084:Oxidation-Reduction; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D002614:Chelating Agents; D056831:Coordination Complexes; D052578:Ionic Liquids; D007477:Ions; D013501:Surface-Active Agents; D003035:Cobalt
keywords: Aggregation; Electron transfer; Entropy; Ionic liquids; Kinetics