A theoretical study on water-assisted excited state double proton transfer process in substituted 2,7-diazaindole-H2O complex

Abstract

The substituted effect on the first excited-state proton transfer (ESPT) process in 2,7-diazaindole-H2O (2,7-DAI-H2O) complex in water was studied in detail at the TD-M06-2X/6–311 + G(d, p) level. The frontier molecular orbital, geometries, reaction mechanism and energies of ESPT process with different substituent have been analyzed. ESPT process in the title complex occurred concertedly but highly asynchronously no matter of the electronic nature of substituent. The absorption and fluorescence peaks, H-bond distances, asynchronicity of ESPT and barrier height were affected by the substituent. The Hammett’s substituent constant had linear correlation with the difference between the sum of N1−O11 and O11−N7 distances in the reactant and that in the TS and Mulliken charge of H3O+.