Tuning phosphorescence features of triphenylamines by varying functional groups and intermolecular interactions

Organic room temperature phosphorescent materials are known for their synthetic feasibility, tunable phosphorescence wavelength and lifetime, etc. Hence new design strategies have been applied on various fluorophores to improve phosphorescence features. Among those, triphenylamines are phosphorescence active due to the presence of nitrogen atom, propeller molecular structure, and intermolecular interactions in the crystal state. Here we have studied the room temperature phosphorescence of a series of triphenylamines with various functional groups. Detailed studies have shown that the phosphorescence can be fine-tuned by functional group modification. A long phosphorescence lifetime around 100 ms at room temperature in air can be achieved by the interplay of intermolecular interactions, singlet-triplet energy gap and extent of intersystem crossing using functional group variation. Interestingly, an exciplex assisted ultralong phosphorescence lifetime (more than 20 times) is observed for a combination of triphenylamine and naphthalenemonoimide in air. •Phosphorescence features of TPA are fine-tuned by functional group modification.•Even though reported TPAs employ polymer support or vacuum, our TPAs exhibit long phosphorescence lifetime in air at room temperature.•A phosphorescence lifetime around 100 ms at room temperature in air can be achieved via functional group variation.•TPA with least lifetime (8 ms) forms an exciplex assisted ultralong phosphorescence along with tunable emission color and improved quantum yield.