La[Fe(CN)₆] ion pairing in aqueous solution. A dielectric relaxation study

Abstract

Complex permittivity spectra of aqueous La[Fe(CN)₆] solutions at 25°C over the frequency range 0.2⩽ν/GHz⩽89 are presented. Because of the large association constant of lanthanum ferricyanide, K_A=5300, and its high ion-pair dipole moment, µ_IP=77.7 D, dilute solutions in the range 0.0026⩽c/mol dm^-3⩽0.0485 could be investigated. It is shown that the current models for the analysis of the ion-pair dispersion amplitude are reliable. The data reveal that the formation of contact ion-pairs is at a nearly diffusion controlled rate, and suggest that the ion-pair activity coefficient deviates from ideality. The effective solvation number of the electrolyte is determined from the solvent permittivity.

References

1. R. Pottel, Ber. Bunsen-Ges. Phys. Chem., 1965, 69, 363.
2. R. Buchner and J. Barthel, Annu. Rep. Prog. Chem., Sect. C: Phys. Chem., 1994, 91, 71.
3. J. Barthel, R. Buchner, P.-N. Eberspächer, M. Münsterer, J. Stauber and B. Wurm, J. Mol. Liq., 1988, 78, 82.
4. J. Barthel, H. Hetzenauer and R. Buchner, Ber. Bunsen-Ges. Phys. Chem., 1992, 96, 1424.
5. E. S. Rittner, J. Chem. Phys., 1951, 19, 1030.
6. E. A. S. Cavell, P. C. Knight and M. A. Sheikh, J. Chem. Soc., Faraday Trans., 1971, 67, 2225.
7. H. S. Dunsmore, T. R. Kelly and G. H. Nancollas, Trans. Faraday Soc., 1963, 59, 2606.
8. R. Buchner and J. Barthel, Ber. Bunsen-Ges. Phys. Chem., 1997, 101, 1509.
9. J. Barthel, K. Bachhuber, R. Buchner, H. Hetzenauer and M. Kleebauer, Ber. Bunsen-Ges. Phys. Chem., 1991, 95, 853.
10. J. Barthel, R. Wachter and H.-J. Gores, in Modern Aspects of Electrochemistry, ed. B. E. Conway and J. O'M. Bockris, Plenum, New York, 1979, vol. 13, p. 1.
11. J. Barthel, H. Hetzenauer and R. Buchner, Ber. Bunsen-Ges. Phys. Chem., 1992, 96, 988.
12. U. Kaatze, J. Mol. Liq., 1993, 56, 95.
13. J. T. Kindt and C. A. Schmuttenmaer, J. Phys. Chem., 1996, 100, 10373.
14. C. Rønne, L. Thrane, P.-O. Åstrand, A. Wallqvist, K. V. Mikkelsen and S. R. Keiding, J. Chem. Phys., 1997, 107, 5319.
15. R. Buchner, J. Barthel and J. Stauber, Chem. Phys. Lett., in press.
16. R. Buchner, G. T. Hefter and J. Barthel, J. Chem. Soc., Faraday Trans., 1994, 90, 2475.
17. J.-C. Lestrade, J.-P. Badiali and H. Cachet, in Dielectric and Related Molecular Processes, ed. M. Davies, The Chemical Society, London, 1975.
18. J. B. Hubbard, P. Colonomos and P. G. Wolynes, J. Chem. Phys., 1979, 71, 2652.
19. A. Chandra and G. N. Patey, J. Chem. Phys., 1994, 100, 8385.
20. L. S. Smith and D. L. Wertz, J. Am. Chem. Soc., 1975, 97, 2365.
21. A. Habenschuss and F. H. Spedding, J. Chem. Phys., 1979, 70, 3758.
22. W. Meier, Ph. Bopp, M. M. Probst, E. Spohr and J.-I. Lin, J. Phys. Chem., 1990, 94, 4672.
23. G. Wilkinson, R. D. Gillard and J. A. McCleverty, Comprehensive Coordination Chemistry, Pergamon, Oxford, 1987, vol. 4.
24. A. Bondi, J. Phys. Chem., 1964, 68, 441.
25. G. A. Krestov, Thermodynamics of Solvation, Ellis Horwood, New York, 1991.
26. K. Fajans and G. Joos, Z. Phys., 1924, 23, 1.
27. J. O'M. Bockris and A. K. N. Reddy, Modern Electrochemistry, Plenum, New York, 1973, vol. 1.
28. (a) W. R. Fawcett and A. C. Tikanen, J. Phys. Chem., 1996, 100, 4251; (b) A. C. Tikanen and W. R. Fawcett, Ber. Bunsen-Ges. Phys. Chem., 1996, 100, 634.
29. J. Barthel, H. Krienke and W. Kunz, Physical Chemistry of Electrolyte Solutions, Steinkoppf/Springer, Darmstadt/New York, 1998.
30. R. Buchner and J. Barthel, J. Mol. Liq., 1995, 63, 55.
31. M. Eigen and K. Tamm, Z. Elektrochem., 1962, 66, 93.
32. J. L. Dote and D. Kivelson, J. Phys. Chem., 1983, 87, 3883.