Rotational dynamics of coumarin 153: Time-dependent friction, dielectric friction, and other nonhydrodynamic effects

Journal Article · Thu Feb 06 04:00:00 EST 1997 · Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory

DOI:https://doi.org/10.1021/jp962921v· OSTI ID:501906

Horng, M L; Gardecki, J A; Maroncelli, M ^[1]

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1. Pennsylvania State Univ., University Park, PA (United States)

Subpicosecond fluorescence anisotropy measurements are used to characterize the rotational dynamics of coumarin 153 (C153) in 35 common solvents and eight solvent mixtures at room temperature. The rotational anisotropy decays of C153 are generally nonexponential as a result of the non-Markovian nature of the friction on its rotational motion. Rotational correlation times are observed to be larger in polar solvents than in nonpolar solvents of the same viscosity. This difference is examined in the context of theories of dielectric friction, which relate the extra friction in polar solute/solvent systems to long-range dipole-dipole interactions. The present data provide a unique opportunity to test general concepts of dielectric friction. Contrary to expectations, the departures from simple hydrodynamic behavior cannot be modeled using only theories of rotational dielectric friction. More important than dielectric friction is the role that the relative solute/solvent size plays in determining the extent of solute-solvent coupling. Once this size dependence is approximately accounted for, the remaining departures from simple hydrodynamic behavior are relatively small in all solvents. In polar aprotic solvents, solvation data indicate that dielectric friction effects should be rather modest (10-20% of the total friction). In these solvents no clear correlation is found between dielectric friction predictions and the observed solute-solvent coupling. 103 refs., 10 figs., 2 tabs.

• OSTI ID: 501906
• Journal Information: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 6 Vol. 101; ISSN 1089-5639; ISSN JPCAFH
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
66 PHYSICS
ABSORPTION SPECTRA
COUMARIN
DIELECTRIC PROPERTIES
EMISSION SPECTRA
FLUORESCENCE
FRICTION
HYDRODYNAMICS
MATHEMATICAL MODELS
PHYSICAL CHEMISTRY
ROTATION
SOLUTIONS