Electron transfer reaction of Tris(1,10-phenanthroline) cobalt(III) complex [Co(phen)3]3+ and thiosulphate ion (S2O32−) in an aqueous acidic medium

  • Authors

    • C R. Osunkwo Ahmadu Bello University, Zaria
    • I U. Nkole Ahmadu Bello University Zaria
    • A D. Onu Federal College of Education Zaria
    • S O. Idris Ahmadu Bello University Zaria
  • Complex, Electron transfer, Kinetics, Thiosulphate ion, Tries (1-10-phenanthroline) cobalt (III).
  • The electron transfer reaction of Tris (1,10-phenanthroline)cobalt(III) complex by thiosulphate ion has been studied in an aqueous acidic medium. Stoichiometric determination shows that for one mole of the oxidant that was reduced, one mole of the reductant was consumed; the reaction conforms to an overall equation:


    2[Co(phen)3]3+ + 2S2O32− → 2[Co(phen)3]2+ + S4O62−


    Kinetics study carried out under pseudo-first order condition shows that the reaction proceeded via a one-way acid-dependent pathway and was third order overall; zero order with respect to the oxidant concentration, second order with respect to the reductant concentration and first order with respect to the hydrogen ion concentration. The empirical rate law conforms to the equation:


    −   {Co(phen)3}3+] = a [H+] [S2O32−]2


    ‘a’ = 128.26 dm6 mol−2 s−1: at [H+] = 2.0 × 10−2 mol dm−3, µ = 0.4 mol dm−3 (NaCl), T = 28 ± 1˚C and λmax = 495 nm.

    The rate of reaction increased at the increase in ionic strength and at the decrease in medium dielectric constant. Added cations and anions catalyzed and inhibited the reaction rates respectively. The Michaelis-Menten plot of 1/k1 versus 1/[S2O32−]2 started from the origin. Hence based on spectroscopic investigation, thermodynamic information from temperature dependence studies and kinetic evidence from Michaelis–Menten plots and the interactions with added ions, an outer-sphere mechanism has been rationalized for this reaction. The mechanistic scheme of the reaction was proposed via the stated mechanistic route.



  • References

    1. [1] Santosh, K. Upadhyay (2006). Chemical Kinetics and Reaction Dynamics. Springer, New York with Anamaya Publishers, New Delhi, India. https://doi.org/10.1080/17415993.2010.550294.

      [2] Asperger, S. (2003). Chemical Kinetics and Inorganic Reaction Mechanism 2nd Edition. Springer Science + Business Media LLC, New York. pp, 3. https://doi.org/10.1007/978-1-4419-9276-5.

      [3] Wang, Q., Huang, M., Huang, Y., Zhang, J.S., Zhou, G.F., Zeng, R.Q., & Yang, X.B. (2014). Synthesis, characterization, DNA interaction, and antitumor activities of mixed-ligand metal complexes of kaempferol and 1, 10-phenanthroline/2, 2′-bipyridine. Medicinal Chemistry Research, 23: 2659–2666. DOI: 10.1007/ s00044-013-0863-2.

      [4] Taube, H. Meyer, H. and Rich, R.L. (1953). Observation on the mechanism of electron transfer in solution. Journal of American Chemical Society, 75:4118. https://doi.org/10.1021/ja01112a546.

      [5] Ahmed, S.K. and Khaled, S. (2015). Syntheses, spectral characterization, thermal properties and DNA cleavage studies of a series of Co(II), Ni(II) and Cu(II) polypyridine complexes with some new imidazole derivatives of 1,10-phenanthroline. Arabian Journal of Chemistry. https://doi.org/10.1016/j.arabjc.2015.04.025.

      [6] Gopinathan, H. and Arumugham, M.N. (2015). Larvicidal activity of synthesized copper (II) complexes against Culex quinquefasciatus and Anopheles subpictus. Journal of Taibah University for Science, 9: 27–33. DOI: https://doi.org/10.1016/j.jtusci.2014.04.008.

      [7] Molphy, Z., Slator, C., Chatgilialoglu, C., & Kellett, A. (2015). DNA oxidation profiles of copper phenanthrene chemical nucleases. Frontiers in Chemistry, 3, 28. DOI: 10.3389/fchem.2015.00028. https://doi.org/10.3389/fchem.2015.00028.

      [8] Gaëlle, D.S., Yufanyi, D.M., Jagan, R. and Agwara, M.O. (2016). Synthesis, Characterization and Antimicrobial properties of Cobalt (II) and Cobalt (III) Complexes derived from one, 10-phenanthroline with Nitrate and Azide co-ligands. Cogent Chemistry, 2: 1253201. https://doi.org/10.1080/23312009.2016.1253201.

      [9] Ukoha, P, O., Atiga, S., Ujam, T. O., Asegbeloyin, J.N., Okpareke, C O. and Okereke, S.O. (2015). Kinetics and Mechanism of Electron Transfer Reaction of an Adipato Bridged Iron (III)-Salen Complex with Dithionite Ion in Perchloric Acid Medium. Croatica. Chemica Acta, 88(3), 259–266. https://doi.org/10.5562/cca2584.

      [10] Onu, A.D., Iyun, J. F. and Idris, S.O. (2015). Kinetics and Stoichiometry of the Reduction of Hydrogen Peroxide by an Aminocarboxylactocobaltate(II) Complex in Aqueous Medium. Open Journal of Inorganic Chemistry, 5: 75-82. https://doi.org/10.4236/ojic.2015.54009.

      [11] Hahn, R.B. and Welcher, F.J. (1963). Inorganic qualitative analysis: A short course for introductory chemistry. Journal of Chemical Education, 40(8), 442. https://doi.org/10.1021/ed040p442.2.

      [12] Patil, R.K., Chimatadar, S.A. and Nandibewoor, S.T. (2008). Oxidation of Thiosulphate by Hexacyanoferrate(III) in aqueous perchloric acid medium – A kinetic and Mechanistic Study. Indian Journal of Chemistry, Vol. 48A, pp357 – 361.

      [13] Byerley, J.J., Fouda, S.A., Rempel, G.L. (1973). Kinetics and Mechanism of the oxidation of Thiosulphates Ions by Copper Ions in Aqueous Ammonia Solution. Journal of Chemical Society, Dalton Transactions. Eight: 889 – 893. Mohammed, Y. (2015). Kinetics and mechanisms of the electron transfer reactions of diaquotetrakis (2, 2’- bipyridine)-µ-oxodiruthenium(III) ions and some reductants in aqueous medium. PhD Thesis submitted to Ahmadu Bello University, Zaria, Nigeria. https://doi.org/10.1039/dt9730000889.

      [14] Dennis, C.R., Leipoldt, J.G., Basson, S.S. and Lamprecht, G.J. (1985). The Oxidation of Thiosulphates Ions by Octacyanotungstate (V) in Weak Acidic Medium. Polyhedron, 4(9): 1621 – 1624.

      [15] Dereven’kov, I.A., Salnikov, D.S., Makarov, S.V., Boss, G.R. and Koifman, O.I. (2013). Kinetics and Mechanism of Oxidation of Super – reduced Cobalamin and Cobinamide species by Thiosulphates, Sulphite and Dithionite. Journal of Chemical Society, Dalton Transactions, 42(43): 15307 – 15316 https://doi.org/10.1016/S0277-5387(00)87238-1.

      [16] Goyal, B., Solanki, S., Arora, S., Prakash, A. and Mehotra, R.N. (1995). Kinetics and Mechanism of the Oxidation of Thiosulphates by Hexachloroiridate(IV). Journal of Chemical Society, Dalton Transactions, 3109 – 3112. DOI: 10.1039/DT9950003109. https://doi.org/10.1039/c3dt51714d.

      [17] Mshelia, M.S., Iyun, J.F., Uzairu, A. and Idris, S. (2010). Kinetics and Mechanism of the Oxidation of Hydrazine Dihydrochloride by Aqueous Iodine. Journal of American Science, 6(9):293-296. https://doi.org/10.1039/dt9950003109.

      [18] Gupta, K.S. and Gupta, Y.K. (1970). Kinetics and Mechanism of the Reduction of Thallium (III) by Hypophosphite. Journal of Chemical Society (A), 256 – 262.

      [19] Pryztas, T.J. and Sutin, N. (1973). Kinetic Studies of Anion – assisted Outer-sphere Electron Transfer Reactions. Journal of American Chemical Society, 95:5545 – 5555. https://doi.org/10.1039/j19700000256.

      [20] James, H. E. (2002), Kinetics and Reaction Mechanisms Second Edition. McGraw – Hill, pp: 156-160. https://doi.org/10.1021/ja00798a020.

      [21] Asemave, K., Yiase, S.G., Adejo, S.O. and Anhwange, B.A. (2012). Substitution Reaction of trans-dichloro-bis- (ethylenediamine) Cobalt (III) Chloride and Phenylalanine - A Kinetics and Mechanism Study. International Journal of Modern Chemistry, 1(2): 93-101.

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    R. Osunkwo, C., U. Nkole, I., D. Onu, A., & O. Idris, S. (2018). Electron transfer reaction of Tris(1,10-phenanthroline) cobalt(III) complex [Co(phen)3]3+ and thiosulphate ion (S2O32−) in an aqueous acidic medium. International Journal of Advanced Chemistry, 6(1), 121-126. https://doi.org/10.14419/ijac.v6i1.11326