Triphenylamine‐Based Bis‐ and Tris‐ESIPT Compounds and Their Boron Complexes: Synthesis, Photophysical Properties and DFT Study of ICT and ESIPT Emissions

Abstract Triphenylamine based bis and tris methoxy and hydroxyl aldehydes, their benzothiazole derivatives and boron complexes were synthesized. Bathochromically shifted keto tautomer emissions were observed for bis and tris hydroxyl aldehyde derivatives in non‐polar solvents such as heptane and toluene while other excited state intramolecular proton transfer (ESIPT) derivatives show only enol emission, where ESIPT effect get suppressed under the increased intramolecular charge transfer (ICT) effect. After boron complexation of ESIPT cores, red shifted emissions with increased quantum yield were reported, implying that the ESIPT compounds are exhibiting only enol emissions and not any keto emissions. We optimized all the derivatives using time dependent density functional theory (TD‐DFT) method and compared their computationally derived photophysical parameters with the experimentally observed ones. Variable twist in the dihedral angle of these compounds in their excited state optimized geometries supported their experimentally observed ICT or ESIPT behaviour.