Effect of temperature on the fluorescence emission of ENCTTTC in different nonpolar solvents1.

The effect of temperature (20-60 °C) on the fluorescence emission of (E)-N-(3-chlorophenyl)-2-(3,4,5-trimethoxybenzylideneamino)-4,5,6,7-tetrahydrobenzo [b]thiophene-3carboxamide (ENCTTTC) is studied in different solvents. It is found that there is no shift in the position of fluorescence maxima, but the intensity decreases with increasing temperature, which depends on the polarity of the solvent. A mechanism of fluorescence quenching with rise in temperature is discussed in terms of the relative location of lowest (ππ*) (nπ*) states and the energy difference between them. The change in temperature brings about a change in the probabilities of radiative and nonradiative transition. The nonradiative deactivation of excited states in the absence of a quencher is temperature dependent and its thermal activation energy has been determined. [ABSTRACT FROM AUTHOR]