Analysis of temperature dependent fluorescence polarization for dimethylaminobenzonitrile

The anisotropy of the fluorescence polarization has been measured as a function of temperature for the dimethylaminobenzonitrile (DMABN) in polar and non-polar solvents. In the electronically excited state, the DMABN molecule undergoes an internal charge-transfer process coupled to a conformational change (Twisted Intramolecular Charge Transfer, or TICT process). The different behaviour exhibited by locally excited (LE) and charge-transfer (CT) bands has been interpreted in terms of an extended Grabowski scheme, in which rotational diffusion of emitting molecules is taken into account.