Skip to main content
SpringerLink
Log in

Thermodynamic changes in the photoinduced proton-transfer reaction of the triplet state of safranine-T

  • Paper
  • Published:
Photochemical & Photobiological Sciences Aims and scope Submit manuscript

abstract

The enthalpy and volume changes occurring in the triplet excited state proton-transfer reactions of safranine-T (SH+) in aqueous solutions at pH 4.8, 8.3, and 10.4 were investigated using time-resolved photoacoustics (TRP). The transient triplet state species were also studied using laser-flash photolysis (LFP). The LFP experiments showed the prompt formation of 3SH+ with a triplet quantum yield FT = 0.28 between pH 4.8 and 10.4. At pH 8.3 3SH+ decays directly to the ground state. However, at pH 4.8 and 10.4, 3SH+ reacts with protons or hydroxy ions to form the dication 3SH22+ or the neutral 3S species, with diffusion-controlled rate constants of kH+ = 1.6 × 1010 M-1 s-1, and kHO- = 2.6 × 1010 M-1 s-1, respectively. Under the same experimental conditions, the TRP measurements allowed the accurate determination of the energy content of the rapidly formed triplet state 3SH+, i.e.ET = 175 kJ mol-1. The slow component (0.1-3 µs) of the TRP signal at pH 4.8 and 10.4 was attributed to the formation of the species 3SH22+ and 3S, respectively. The enthalpy changes associated with the proton-transfer reactions of 3SH+, calculated from the values of the heat released as obtained by TRP, were in remarkable agreement with the values estimated from the thermodynamic data of the acid-base equilibria of the triplet states of the dye. The formation of 3SH+ was accompanied by a volume expansion of 1.8 cm3 mol-1, which was explained by changes in the hydrogen-bonding interaction of the dye with its solvation sphere. Instead, the volume changes observed upon the formation of 3SH22+ and 3S accounted for the electrostrictive effect produced by the change in the charge distribution on the dye after the proton-transfer reaction.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  1. S. E. Braslavsky and G. E. Heibel, Time-resolved photothermal and photoacoustic methods applied to photoinduced processes in solution, Chem. Rev., 1992, 92, 1381–1410.

    Article  CAS  Google Scholar 

  2. S. G. Bertolotti and C. M. Previtali, The excited states quenching of safranine T by p-benzoquinones in polar solvents, J. Photochem. Photobiol., A, 1997, 103, 115–119.

    Article  CAS  Google Scholar 

  3. S. D.-M. Islam, M. Fujitsuka and O. Ito, Photochemical reactions of triplet state of safranine-T studied by transient absorption spectroscopy in visible/near-IR regions, Phys. Chem. Chem. Phys., 1999, 1, 3737–3742.

    Article  CAS  Google Scholar 

  4. H.-J. Timpe and S. Neuenfeld, Photoreduction of some dyes by styrene, J. Chem. Soc., Faraday Trans., 1992, 88, 2329–2336.

    Article  CAS  Google Scholar 

  5. C. M. Previtali, S. G. Bertolotti, M. G. Neumann, I. A. Pastre, A. M. Rufs and M. V. Encinas, Laser flash photolysis study of the photoinitiator system Safranine T—aliphatic amines for vinyl polimerization, Macromolecules, 1994, 27, 7454–7458.

    Article  CAS  Google Scholar 

  6. M. V. Encinas, A. M. Rufs, M. G. Neumann and C. M. Previtali, Photoinitiated vinyl polymerization by safranine T/triethanolamine in aqueous solution, Polymer, 1996, 37, 1395–1398.

    Article  CAS  Google Scholar 

  7. C. E. Baumgartner, H. H. Richtol and D. A. Aikens, Transient photochemistry of safranine-O, Photochem. Photobiol., 1981, 34, 17–22.

    Article  CAS  Google Scholar 

  8. I. A. Pastre and M. G. Neumann, The effect of microheterogeneous domains in the protonation of the triplet state of safranine-T, J. Colloid Interface Sci., 1996, 179, 227–232.

    Article  CAS  Google Scholar 

  9. D. Madge, J. H. Brannon, T. L. Cremers and J. Olmsted, Absolute luminiscence yield of cresyl violet. A standard for the red, J. Phys. Chem., 1979, 83, 696–699.

    Article  Google Scholar 

  10. J. R. Lakowicz, Principles of fluorescence spectroscopy, 2nd edn., Kluwer Academic/Plenum Publisher, New York, 1999, p. 52.

    Book  Google Scholar 

  11. C. D. Borsarelli, J. J. Cosa and C. M. Previtali, Interface effect on the properties of exciplexes formed between pyrene derivatives and N, N-dimethylaniline in reverse micelles, Langmuir, 1993, 9, 2895–2901.

    Article  CAS  Google Scholar 

  12. C. D. Borsarelli, S. E. Braslavsky, S. Sortino, G. Marconi and S. Monti, Photodecarboxylation of ketoprofen in aqueous solution. A time-resolved laser-induced optoacoustic study, Photochem. Photobiol., 2000, 72, 163–171.

    Article  CAS  Google Scholar 

  13. J. E. Rudzki, J. L. Goodman and K. S. Peters, Simultaneous determination of photoreaction dynamics and energetics using pulsed, time-resolved photoacoustic calorimetry, J. Am. Chem. Soc., 1985, 107, 7849–7854.

    Article  CAS  Google Scholar 

  14. A. Losi and C. Viappiani, Reaction volume and rate constants for the excited-state proton transfer in aqueous solutions of naphthols, Chem. Phys. Lett., 1998, 289, 500–506.

    Article  CAS  Google Scholar 

  15. M. V. Encinas and C. M. Previtali, S. G. Bertolotti, M. G. Neumann, The interaction of the excited states of safranine-T with aliphatic amines in organic solvents, Photochem. Photobiol., 1995, 62, 65–70.

    Article  CAS  Google Scholar 

  16. F. Wilkinson, Chemical kinetics and reaction mechanisms, Van Nostrand Reinhnold Co. Ltd., New York, 1980, p. 86.

    Google Scholar 

  17. I. Carmichael and G. L. Hug, Triplet-Triplet absorption spectra of organic molecules in condensed phases, J. Phys. Chem. Ref. Data, 1986, 15, 1–250.

    Article  Google Scholar 

  18. S. L. Murov, I. Carmichael and G. L. Hug, Handbook of Photochemistry, 2nd edn., Marcel Dekker, New York, 1993.

    Google Scholar 

  19. R. C. Weast, ed. CRC Handbook of Chemistry and Physics, 67th edn., CRC Press, Boca Raton, FL, 1986-1987, p. F–4.

    Google Scholar 

  20. M. S. Churio, K. P. Angermund and S. E. Braslavsky, Combination of laser-induced optoacoustic spectroscopy (LIOAS) and semiempirical calculations for the determination of molecular volume changes. The photoisomerization of carbocyanines, J. Phys. Chem., 1994, 98, 1776–1782.

    Article  CAS  Google Scholar 

  21. A. A. Frost and R. G. Pearson, Kinetics and Mechanism, 2nd edn., J. Wiley, New York, 1961.

    Google Scholar 

  22. R. A. Alberty and F. Daniels, Physical Chemistry, 5th edn., J. Wiley, New York, 1979.

    Google Scholar 

  23. R. Schmidt and M. Schütz, Determination of reaction volumes and reaction enthalpies by photoacoustic calorimetry, Chem. Phys. Lett., 1996, 263, 795–802.

    Article  CAS  Google Scholar 

  24. R. Schmidt, Interpretation of reaction and activation volumes in solution, J. Phys. Chem. A, 1998, 102, 9082–9086.

    Article  CAS  Google Scholar 

  25. Y. Yoshimura and M. Nakahara, Molecular theory of the volume change accompanying contact-complex formation reactions in solution, J. Chem. Phys., 1984, 81, 4080–4086.

    Article  CAS  Google Scholar 

  26. C. D. Borsarelli and S. E. Braslavsky, Volume changes correlate with enthalpy changes during the photoinduced formation of the MLCT state of ruthenium(ii) bipyridine cyano complexes in the presence of salts. A case of entropy-enthalpy compensation effect, J. Phys. Chem. B, 1998, 102, 6231–6238.

    Article  CAS  Google Scholar 

  27. E. Whalley, Some comments on electrostatic volumes and entropies of solvation, J. Chem. Phys., 1963, 38, 1400–1405.

    Article  CAS  Google Scholar 

  28. S. Hamann, in Modern Aspects of Electrochemistry, eds. B. E. Conway and J. O. M. Bockris, Plenum Press, New York, Chapter 2, 1974.

  29. C. D. Borsarelli and S. E. Braslavsky, The partial molar volume of the proton in water determined by laser-induced optoacoustic studies, J. Photochem. Photobiol., B, 1998, 43, 222–228.

    Article  CAS  Google Scholar 

  30. M. Terazima, Reaction enthalpy and reaction volume changes upon photoenolization: 2-methylbenzophenone, J. Phys. Chem. A, 1998, 102, 545–551.

    Article  CAS  Google Scholar 

  31. T. Gensch and S. E. Braslavsky, Volume changes related to triplet formation of water-soluble porphyrins. A laser-induced optoacoustic spectroscopy (LIOAS) study, J. Phys. Chem. B, 1997, 101, 101–108.

    Article  CAS  Google Scholar 

  32. F. Millero, The molal volume of electrolytes, Chem. Rev., 1971, 71, 147–176.

    Article  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Instituto de Ciencias Químicas, Universidad Nacional de Santiago del Estero, Av. Belgrano (S) 1912., 4200, Santiago del Estero, Argentina

    Claudio D. Borsarelli

  2. Departamento de Química y Física, Universidad Nacional de Río Cuarto, Río Cuarto, Argentina

    Sonia G. Bertolotti & Carlos M. Previtali

Authors
  1. Claudio D. Borsarelli
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Sonia G. Bertolotti
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Carlos M. Previtali
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Claudio D. Borsarelli.

Additional information

† Dedicated to Professor Silvia E. Braslavsky on the occasion of her 60th birthday.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Borsarelli, C.D., Bertolotti, S.G. & Previtali, C.M. Thermodynamic changes in the photoinduced proton-transfer reaction of the triplet state of safranine-T. Photochem Photobiol Sci 1, 574–580 (2002). https://doi.org/10.1039/b202683j

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1039/b202683j

Search

Navigation