Excess dynamic Stokes shift of molecular probes in solution.
J Phys Chem B
; 117(25): 7675-84, 2013 Jun 27.
Article
em En
| MEDLINE
| ID: mdl-23721291
ABSTRACT
The solvation dynamics of molecular probes is studied by broad-band fluorescence upconversion. The time-dependent position of the S1 â S0 emission band or of a vibronic line shape is measured with ~80 fs, 10 cm(-1) resolution. Polar solutes in acetonitrile and acetone, when excited into S1 with excess vibrational energy, show a dynamic Stokes shift which extends to the red beyond the quasistationary state. Equilibrium is then reached by a slower blue shift on a 10 ps time scale. In methanol, excess vibrational energy as large as ~14,000 cm(-1) shows no such effect. Nonpolar solutes exhibit an excess red shift of the emission band in both polar and nonpolar solvents even upon excitation near the vibronic origin. The observed dynamics are discussed in terms of transient heating of the excited chromophore, conformational change, and changes of the molecular cavity size. For solvation studies the optical excitation should be chosen close to the band origin.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
J Phys Chem B
Assunto da revista:
QUIMICA
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Alemanha