Dynamic solvatochromism in solvent mixtures*
Diana E. Wetzler1, Carlos Chesta2, Roberto Fernández-Prini13,
and Pedro F. Aramendía1**
1INQUIMAE, DQIAQF,
FCEN, Universidad de Buenos Aires, C. Universitaria, 1428 Buenos Aires,
Argentina; 2Dept de Química, Universidad Nacional
de Río Cuarto, 5800 Río Cuarto, Argentina; 3Unidad
de Actividad Química, CNEA, Libertador 8250 1428 Buenos Aires,
Argentina
Abstract: Solvatochromism and thermochromism of 4-aminophthalimide
and 4-amino-N-methylphthalimide were studied by absorption and
steady-state and time-resolved emission spectroscopy in solvent mixtures
of tolueneethanol and tolueneacetonitrile at different temperatures.
Emission spectra shift to the red upon addition of a polar solvent (PS)
to toluene. Solvent mixtures show a much greater thermochromic shift
to the blue in emission than the neat solvents. This is explained by
the decrease in temperature of the exothermic association of the polar
solvent to the excited state. Emission spectra are time dependent in
solvent mixtures in the ns timescale. The time evolution of this emission
is interpreted on the basis of the different solvation of the ground
state and the emitting excited state. SternVolmer plots are obtained
for the dependence of the spectral-shift characteristic time with [PS].
*Lecture presented at the XVIIIth IUPAC Symposium on
Photochemistry, Dresden, German , 22-27 July 2000.Other presentations
are published in this issue, pp.395-548.
** Corresponding author