Polarization anisotropy applied to the determination of structural changes in the photoisomerization of DODCI Original Research Article

The steady-state fluorescence anisotropy of the photoisomerizable dye 3,3′-diethyloxadicarbocyanine iodide (DODCI) in ethanol, was studied as a function of temperature, in order to determine its molecular conformation. Dual laser excitation was used to separate the emission of the normal species from that of its photoisomer. This permitted us to follow separately the fluorescence anisotropy of both species. The results were analyzed with stick-slip hydrodynamic boundary conditions and asymmetric ellipsoids were used to simulate the molecular shape. Results were in agreement with those predicted from with slip hydrodynamic boundary conditions, allowing to get a possible conformational assignation to those species of DODCI that take part in the photoisomerization process.