Static and Dynamic Properties of Quinoxalines in the Phosphorescent Triplet State from Optically Detected Magnetic Resonance

Abstract

Abstract The static and dynamic properties of the phosphorescent triplet states of quinoxaline and 2,3-disubstituted derivatives in hexane have been studied at 1.4 K using the methods of optically detected magnetic resonance. In addition, the absorption and phosphorescence excitation spectra have also been measured to attain the information about the low lying excited states. A systematic comparison has been made for the purpose of examining the effect of substitution. A significant enhancement of the pumping rates for the y spin sublevel observed in the chlorinesubstituted derivatives is concluded to be due to the additional indirect process of intersystem crossing which occurs from S1 of n,π* to T1 passing through the intermediate triplet state of π,π*. A detailed discussion on the observed phosphorescence spectra originating from the three sublevels has achieved a satisfactory success in understanding the mechanisms responsible for the radiative decay processes. It is concluded that the mechanisms due to vibronic coupling with closely lying n,π* triplet states are of little importance in the systems studies here.