ROTATIONAL RELAXATION OF PYRAZOLINE COMPOUNDS IN SOLUTION

The photophysical behaviour of pyrazoline derivatives was studied in this work. The fluorescence quantum yields of these compounds were measured in various media with identical polarity but different viscosity. In accordance with microviscosity theory, a linear relationship was observed between the product of the non-radiative decay rate constant and solvent viscosity and eta(x). It is suggested that the process of non-radiative decay occurs via rotation of the phenyl group which is connected to the N-1 position in the diphenyl pyrazoline molecule.