Excited-state intramolecular single and double proton transfer emission of 2,5-bis(benzoxazol-2-yl)thiophene-3,4-diol

• 2,5-bis(benzoxazol-2-yl)thiophene-3,4-diol as a model compound is prepared.
• Excited-state intramolecular single/double proton transfer emission is presented.
• The effect of solvents on excited-state intramolecular proton transfer emission is explored.

In this work, excited-state intramolecular single proton transfer emission (S-PTE) and double proton transfer emission (D-PTE) are presented by employing 2,5-bis(benzoxazol-2-yl)thiophene-3,4-diol (1) as a prototype. 1 has been strategically designed and synthesized in an aim to explore single proton transfer and double proton transfer in the excited state. In solution 1 exhibits the lowest lying S0 → S1 absorption at ∼395 nm. Upon excitation, two large Stokes shifted emission bands maximized at 475 nm and 550 nm are resolved, which are ascribed to the tautomer emission resulting from single proton transfer and double proton transfer isomers, respectively. It is found that solvents have greatly influenced on excited-state intramolecular proton transfer emission.

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