Excited‐state Intramolecular Proton–transfer‐induced Charge Transfer of Polyquinoline

Abstract

The excited-state intramolecular proton-transfer-induced charge transfer of semirigid polyquinoline (PQH) is explored in 1,1,2,2-tetrachloroethane (TCE) and N-methyl-2-pyrrolidinone (MP) using picosecond time-resolved fluorescence spectroscopy. Reaction mechanisms are found to depend on the rotational conformations of PQH at the moment of excitation; whereas the trans-enolic form does not undergo intramolecular proton transfer within its excited-state lifetime, the cis-enolic form does within 15 ps to form a tautomeric zwitterion species. While the subsequent intramolecular charge transfer of the zwitterionic species to yield a tautomeric keto species takes place on time scales of 25 ps in TCE (ε = 8.50) and 62 ps in MP (ε = 32.55), its reverse reaction is also followed on time scales of 28 ps in TCE and 20 ps in MP. The lack of a kinetic isotope effect in both forward and reverse charge-transfer reactions support our proposed mechanisms.

The theoretical study of excited-state intramolecular proton transfer of 2,5-bis(benzoxazol-2-yl)thiophene-3,4-diol

“…Hydrogen bond has been diffusely researched in recent decades, which is ubiquitous in photophysics, photochemistry and photobiology [1][2][3][4][5][6][7][8][9][10][11]. Some microscopic frameworks of molecular and supramolecular involve the hydrogen bond interaction, for example, the polymers, the complex structures of solute and solvent, proteins and DNA, etc.…”