Effects of organised media on the excited-state proton transfer in 2-(2′-pyridyl)benzimidazole

Abstract

Absorption and fluorescence characteristics of 2-(2′-pyridyl)benzimidazole (2-PBI) are studied in the presence of α- and β-cyclodextrins (CD) in aqueous solution at two different pHs. Steady-state and time-resolved fluorescence measurements are used for the investigation of the effect of organised media on the excited-state proton transfer reaction in 2-PBI. Semi-empirical CI calculation for the geometry of the molecule reveals that the 2-PBI molecule may be involved in host–guest complex formation with α-CD and β-CD in different configurations. NMR measurements corroborate this, providing information about the orientation of the 2-PBI molecule inside the cavity of the CDs. No complex formation was evident in γ-CD owing to its larger cavity dimension compared to the size of the 2-PBI molecule.

References

1. C. A. S. Potter and R. G. Brown, Chem. Phys. Lett., 1988, 153, 7.
2. H. K. Sinha and S. K. Dogra, Bull. Chem. Soc. Jpn., 1989, 62, 2668.
3. H. K. Sinha and S. K. Dogra, Spectrochim. Acta, Part A, 1989, 45, 1289.
4. K. Das, N. Sarkar, A. K. Ghosh, D. Majumdar, D. N. Nath and K. Bhattacharyyaa, J. Phys. Chem., 1994, 98, 9126.
5. A. Douhal, F. Amat-Guerri, A. U. Acuna and K. Yoshihara, Chem. Phys. Lett., 1994, 217, 619.
6. A. Douhal, F. Amat-Guerri, M. P. Lillo and A. U. Acuna, J. Photochem. Photobiol. A, 1994, 78, 127.
7. R. Duchowicz, M. Ferrer, F. Amat-Guerri, R. Sastre and A. U. Acuna, Opt. Commun., 1994, 104, 336.
8. M. L. Ferrer, A. U. Acuna, F. Amat-Guerri, A. Costela, J. M. Figuera, F. Florido and R. Sastre, Appl. Opt., 1994, 33, 2266.
9. F. R. Prieto, M. Mosquera and M. Novo, J. Phys. Chem., 1990, 94, 8536.
10. M. Novo, M. Mosquera and F. R. Prieto, J. Phys. Chem., 1995, 99, 14726.
11. J. F. Ireland and P. A. H. Wyatt, Adv. Phys. Org. Chem., 1978, 12, 131.
12. D. A. Parthenopoulos and M. Kasha, Chem. Phys. Lett., 1988, 146, 77.
13. A. U. Acuna, A. Costela and J. M. Munoz, J. Phys. Chem., 1986, 90, 2807.
14. W. Klopffer, Adv. Photochem., 1977, 10, 311.
15. M. Kondo, Bull. Chem. Soc. Jpn., 1978, 51, 3027.
16. R. G. Brown, N. Entwistle, J. D. Hepworth, K. W. Hodgson and B. May, J. Phys. Chem., 1982, 86, 2418.
17. J. M. Schutte, T. Ndou, A. Munoz de la Pena, K. L. Greene, C. K. Williamson and I. M. Warner, J. Phys. Chem., 1991, 95, 4897.
18. A. Munoz de la Pena, T. Ndou, J. B. Zung and I. M. Warner, J. Phys. Chem., 1991, 95, 3330.
19. T. Yorozu, M. Hoshimo, M. Imamura and H. Shizuka, J. Phys. Chem., 1982, 86, 4422.
20. E. L. Roberts, P. T. Chou, A. Alexander, R. A. Agbaria and I. M. Warner, J. Phys. Chem., 1995, 99, 5431.
21. J. E. Hansen, E. Pines and G. R. Fleming, J. Phys. Chem., 1992, 96, 6904.
22. S. Li and W. C. Purdy, Chem. Rev., 1992, 92, 1457.
23. W. H. Melhuish, J. Phys. Chem., 1961, 65, 229.
24. H. A. Benesi and J. H. Hildebrand, J. Am. Chem. Soc., 1949, 71, 2703.
25. V. Ramamurthy, Tetrahedron, 1986, 42, 5753.
26. W. P. Jencks, Acc. Chem. Res., 1976, 9, 425.