Photo-oxidation of indenylidene-dihydropyridine derivatives: Conical intersection manipulation by solvent polarity

PHYS 394

Semyon Cogan,, Yehuda Haas,, and Shmuel Zilberg, Physical Chemistry Dep, The Hebrew University in Jerusalem, Giv'at Ram, 91904 Jerusalem, Israel
The main motivation of the research was to perform experimental study of solvent polarity influence on relaxation processes through conical intersections. Model Quantum mechanical calculations predict different solvent polarity effect on relaxation processes in the case of Ortho- and Para-Indenylidene-dihydropyridine derivatives. This prediction was tested by photo-oxidation experiments in different solvents. The study of photo-oxidation process of both systems shows that high lying triplets are involved as there is a pronounced wavelength effect on photo-bleaching process that competes with extremely efficient relaxation process. This is Kasha's rule violation, which is usually observed for the systems with ultra-fast relaxation from first excited states to the ground state. The experimental investigation of the solvent effect in these systems showed that while in the case of Para-systems the relaxation processes are slowed in polar solvents, the Ortho-system's behavior is the opposite. We assign this abnormal behavior of the Para-systems to removal of the CI degeneracy by electrostatic interactions with solvent while in the case of the Ortho-system there is no Conical Intersection, as was predicted by quantum mechanical calculations.

Poster Session
7:30 PM-10:00 PM, Wednesday, 13 September 2006 Moscone Center -- Hall D, Poster

8:00 PM-10:00 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Sci-Mix

Division of Physical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006