VISCOSITY DEPENDENCE OF THE ROTATIONATIONAL REORIENTATION OF COUMARINS BY DEPOLARIZATION TECHNIQUE

Steady-state and time-resolved fluorescence behavior of coumarin 6 (C6) and coumarin 7 (C7) in alkane and alcohol solvents has been investigated. Steady-state absorption and emission spectral behavior of C6 and C7 is found not to be affected by the both the solvents. Time-resolved fluorescence anisotropy measurements show that the rotational reorientation of the probe becomes faster in alcohol. A comparison of the experimentally measured rotational reorientation times of C6 and C7 are identical in a given solvents at a particular temperature. The present study has been undertaken to examine the role of friction experienced by the polar solutes in a polar and non-polar solvents. Molecular shape and size are similar but the friction experienced by these probes in ntridecane and n-propanol solvents viscosities were varies by temperature. However, it was observed that C6 and C7 rotates faster in alcohol than alkane and the observed results are discussed in the last section.