Spectroscopic (UV/VIS, resonance Raman) and spectroelectrochemical study of platinum(II) complexes with 2,2′-bipyridine and aromatic thiolate ligands 

Abstract

A series of complexes [Pt(bpy)(4-XC₆H₄S)₂] (bpy = 2,2′-bipyridine; X = NO₂, H, MeO or Me₂N) have been synthesized and characterised spectroscopically. All absorb moderately in the visible region; the molar absorption coefficients of the solvatochromic absorption band lie below the values for the corresponding dithiolate complexes, indicating a slightly distorted planar geometry and a smaller HOMO – LUMO overlap. Resonance Raman, cyclic voltammetric and UV/VIS spectroelectrochemical experiments were carried out to confirm the charge transfer-to-diimine character of the visible electronic transition(s) directed from a p(S)–π(Ph)/d(Pt) delocalised orbital manifold to the π₁* LUMO of the 2,2′-bipyridine ligand. Consistent with this bonding situation: (i ) the reduction of [Pt(bpy)(4-XC₆H₄S)₂] is initially localised on the bpy ligand; for X = NO₂ the second and third added electrons enter the vacant π* orbitals on the 4-NO₂ substituents; (ii) the resonance Raman spectra of [Pt(bpy)(4-MeOC₆H₄S)₂] show, besides the internal bpy modes, only a weak effect for intrathiolate (Ph–S) and ν(Pt–S) vibrations; and (iii) the oxidation is initially a one-electron process due to electronic interaction of the thiolate ligands through the platinum centre. The strongly thiolate-dependent oxidation potentials indicate a prevailing thiolate character of the HOMO.

References

1. (a) T. J. Meyer, in Photochemical Processes in Organized Molecular System, ed. K. Honda, Elsevier, Amsterdam, 1991, p. 133; (b) V. Balzani, S. Campagna, G. Denti, A. Juris, S. Serroni and M. Venturi, Coord. Chem. Rev., 1994, 132, 1; (c) K. Kalyanasundaram, Coord. Chem. Rev., 1982, 46, 159; (d) P. R. Auburn and A. B. P. Lever, Inorg. Chem., 1990, 29, 2551.
2. (a) A. Harriman and R. Ziessel, Chem. Commun., 1996, 1707; (b) V. Grosshenny, A. Harriman, M. Hissler and R. Ziessel, J. Chem. Soc., Faraday Trans., 1996, 2223; (c) A. Harriman, M. Hissler, R. Ziessel, A. De Cian and J. Fisher, J. Chem. Soc., Dalton Trans., 1995, 4067; (d) P. I. Kvam, M. I. V. Puzyk, V. S. Cotlyr, J. Songstang and K. P. Balashev, Acta Chem. Scand., 1996, 50, 6; (e) H. Kunkely and A. Vogler, Inorg. Chim. Acta, 1997, 264, 305; (f) S. P. Kaiwar, A. Vodachek, N. V. Blough and R. S. Pilato, J. Am. Chem. Soc., 1997, 119, 9211.
3. (a) J. A. Zuleta, J. Bevilacqua and R. Eisenberg, Coord. Chem. Rev., 1991, 111, 237; (b) J. A. Zuleta, M. S. Burberry and R. Eisenberg, Coord. Chem. Rev., 1990, 97, 47; (c) J. Bevilacqua and R. Eisenberg, Inorg. Chem., 1994, 33, 2913; (d) S. D. Cummings and R. Eisenberg, Inorg. Chem., 1995, 34, 2007; (e) S. D. Cummings and R. Eisenberg, J. Am. Chem. Soc., 1996, 118, 1949; (f) J. A. Zuleta, J. Belvilacqua, D. M. Prosperio, P. D. Harvey and R. Eisenberg, Inorg. Chem., 1992, 31, 2396; (g) S. D. Cummings, L.-T. Cheng and R. Eisenberg, Chem. Mater., 1997, 9, 440; (h) J. Weinstein, M. Mel'nikov, V. Plyusnin and V. Grivin, unpublished work; (i) A. M. Gallin, Yu. V. Razskazovsky and M. Ya. Mel'nikov, J. Photochem. Photobiol. A: Chem., 1994, 78, 113.
4. (a) K.-D. Asmus, in Sulfur-Centered Reactive Intermediates in Chemistry and Biology, eds. C. Chatgilialoglu and K.-D. Asmus, NATO-ASI Series, Plenum, New York, 1991 and refs. therein; (b) M. Gobl, M. Bonifacic and K.-D. Asmus, J. Am. Chem. Soc., 1984, 106, 5984; (c) D. A. Armstrong, ref. 4(a), pp. 121–134 and 341–351.
5. S. M. Frederics, J. C. Luong and M. S. Wrighton, J. Am. Chem. Soc., 1979, 101, 7415; M. Martin, M.-B. Krogh-Jespersen, M. Hsu, J. Tewksbury, M. Laurent, K. Viswanath and H. Patterson, Inorg. Chem., 1983, 22, 647.
6. (a) M. P. Aarnts, M. P. Wilms, K. Peelen, J. Fraanje, K. Goubitz, F. Hartl, D. J. Stufkens, E. J. Baerends and A. Vlček, jun., Inorg. Chem., 1996, 35, 5468; (b) B. D. Rossenaar, F. Hartl and D. J. Stufkens, Inorg. Chem., 1996, 35, 6194; (c) F. Hartl and A. Vlcek, jun., Inorg. Chem., 1991, 30, 3048.
7. A. Klein and W. Kaim, Organometallics, 1995, 14, 1176.
8. A. M. Galin, Y. V. Razskazovskii and M. Ya. Mel'nikov, Russ. J. High Energy Chem., 1993, 27, 69.
9. G. T. Morgan and F. H. Burstal, J. Chem. Soc., 1934, 965.
10. M. Krejčík, M. Daneěk and F. Hartl, J. Electroanal. Chem., Interfacial Electrochem., 1991, 313, 243.
11. G. Gritzner and J. Kuta, Pure Appl. Chem., 1984, 56, 461.
12. R. S. Stojanovic and A. M. Bond, Anal. Chem., 1993, 65, 56.
13. N. Zheligovskaya, L. Kopaneva and E. Pomakhina, Russ. J. Coord. Chem., 1995, 21, 570.
14. A. Vogler and H. Kunkely, J. Am. Chem. Soc., 1981, 103, 1559; Inorg. Chem., 1982, 21, 1172; A. Vogler, H. Kunkely, J. Hlavatsch and A. Merz, Inorg. Chem., 1984, 23, 506; H. Kunkely and A. Vogler, J. Am. Chem. Soc., 1990, 112, 5625.
15. D. M. Manuta and A. J. Lees, Inorg. Chem., 1983, 22, 3825.
16. F. Hartl, T. L. Snoeck, D. J. Stufkens and A. B. P. Lever, Inorg. Chem., 1995, 34, 3887 and refs. therein.
17. K. Nakamoto, in Infrared and Raman Spectra of Inorganic and Coordination Compounds, Wiley, New York, 5th edn., 1997, part B.
18. D. J. Stufkens, T. L. Snoeck and B. J. van der Veken, Inorg. Chim. Acta, 1983, 76, L253; J. R. Alkins and P. J. Hendra, J. Chem. Soc. A, 1967, 1325.
19. R. A. Klein, C. J. Elsevier and F. Hartl, Organometallics, 1997, 16, 1284.
20. D. E. Bartak, T. M. Shields and M. D. Hawley, J. Electroanal. Chem., Interfacial Electrochem., 1971, 30, 289.
21. (a) M. Krejčík and A. A. Vlček, J. Electroanal. Chem., Interfacial Electrochem., 1991, 313, 243; (b) J. Víchová, F. Hartl and A. Vlcek, jun., J. Am. Chem. Soc., 1992, 114, 10 903; (c) B. C. Noble and R. D. Peacock, Spectrochim. Acta, Part A, 1990, 46, 407.
22. C. Amatore, M. Azzabi, P. Calas, A. Jutand, C. Lefrou and Y. Rollin, J. Electroanal. Chem., Interfacial Electrochem., 1990, 288, 45.
23. A. J. Bard and L. R. Faulkner, in Electrochemical Methods: Fundamentals and Applications, Wiley, New York, 1980, p. 218.
24. R. Benedix and H. Hennig, Inorg. Chim. Acta, 1988, 141, 21.
25. L. Kumar, K. H. Puthraya and T. S. Shrivastava, Inorg. Chim. Acta, 1984, 86, 173.
26. G. Matsubayashi, Y. Yamaguchi and T. Tanaka, J. Chem. Soc., Dalton Trans., 1988, 2216.
27. (a) R. Rafikov, J. Weinstein, M. Mel'nikov and N. Zheligovskaya, unpublished work; (b) Absorption Spectra in Ultraviolet and Visible Region, ed. L. Lang, Akademiai, Budapest, 1971, vol. 15, pp. 127–128.
28. R. M. Wallac and S. M. Katz, J. Phys. Chem., 1964, 68, 3890.
29. Y. Zhang, K. D. Ley and K. S. Schanze, Inorg. Chem., 1996, 35, 7102.
30. K. Base and M. W. Grinstaff, Inorg. Chem., 1998, 37, 1432.
31. D. J. Stufkens, T. L. Snoeck and A. B. P. Lever, Inorg. Chem., 1988, 27, 953.