Molecular Engineering of Excited-state Intramolecular Proton Transfer (ESIPT) Dual and Triple Emitters

Excited-State Intramolecular Proton Transfer (ESIPT)-capable emitters have been in the limelight in the past few years owing to their atypical photophysical features paving the way to the engineering of innovative applications. ESIPT emission originates from a proton transfer occurring in the electronic excited-state which can be partially frustrated by multiple factors leading to finely tunable dual emission profiles that are highly dependent on the physical properties of the environment. Moreover, in specific cases, stable deprotonated species can be spectroscopically observed. This highlight review focuses on recent developments in the field of dual and triple emissive ESIPT emitters with an emphasis on the influence of chemical substitution on the frustration of the proton transfer process, as well as other beneficial parameters such as solvatation, crystallization and external stimuli. Theoretical aspects and in particular ab initio calculations of the excited-state energies of the various tautomers are discussed as well.