Excited state intramolecular proton transfer fluorescence emission of o-hydroxyphenyl-triazine derivatives

Abstract

o-hydroxyphenyl-triazine derivatives with formyl substituents were surveyed for the excited state intramolecular proton transfer (ESIPT). The occurrence of ESIPT was confirmed by well-separated emission bands for the derivatives. A low energy change from enol to keto in the excited state explains ESIPT for the derivatives. xyphenyl-triazine derivatives have alkyl or aryl substituents on the hydroxyphenyl ring [7][8][9][10]. The electron-donating nature of alkyl or aryl groups could reduce the acidity of the hydroxy group and lower the possibility of ESIPT occurrence. In contrast, the acidity of the hydroxy group could be enhanced by electron withdrawing group, which would facilitate ESIPT. We recently investigated the occurrence of ESIPT in novel o-hydroxyphenyl-triazine derivatives (Figure 1, C1: 2-(2-hydroxy-5-formal-dehyde)-2H-benzotriazole, C2: 2-(2-methoxy-5-formalde-hyde)-2H-benzotriazole), which contained a formyl substituent on the hydroxyphenyl ring. To our knowledge, this is the first direct observation of the ESIPT emission of o-hydroxyphenyl-triazine derivatives.

Study on ESIPT process of fluorescence probe BT-ITC for detecting H2S in DMF/H2O mixed solution

“…In an extremely quick process, ESIPT reaction will produce a tautomer because the proton is moved from proton donor of the reactant molecule to the neighboring site of the proton acceptor. [8][9][10][11][12]. Based on this photo-physical property, most fluorescent chemical sensors are designed by perturbing the ESIPT process [13][14][15][16][17][18][19][20][21].…”