Structural and Photoluminescence Properties of Excited State Intramolecular Proton Transfer Capable CompoundsPotential Emissive and Electron Transport Materials

Electronic factors influencing the photoluminescence properties and rates of excited state intramolecular proton transfer (ESIPT) reaction of o-hydroxy derivatives of 2,5-diphenyl-1,3,4-oxadiazole have been studied. The potential of these molecules as emissive and electron transport materials in designing improved organic light emitting diodes (OLEDs) has been studied by analyzing possible reasons for the unusually high Stokes shifts and ESIPT reaction rates. Time-dependent density functional theory (TDDFT) methods have been used to calculate the ground and excited state properties of the phototautomers that are the ESIPT reaction products. We study the relative effect of electron-withdrawing substituents on the proton-acceptor moiety and predict that the lowest ESIPT rate (1.9 × 10¹¹ s^-1) is achieved with a dimethylamino substituent and that the Stokes shifts are around 11 000 cm^-1 for all three derivatives.