Effect of different alkyl groups on excited-state tautomerization of 7AI-azaindole-H2O: A theoretical study

Jiacheng Yi; Hua Fang

doi:10.1016/j.saa.2018.05.037

Effect of different alkyl groups on excited-state tautomerization of 7AI-azaindole-H₂O: A theoretical study

Spectrochim Acta A Mol Biomol Spectrosc. 2018 Sep 5:202:58-64. doi: 10.1016/j.saa.2018.05.037. Epub 2018 May 16.

Authors

Jiacheng Yi¹, Hua Fang²

Affiliations

¹ Department of Chemistry and Material Science, College of Science, Nanjing Forestry University, Nanjing 210037, People's Republic of China.
² Department of Chemistry and Material Science, College of Science, Nanjing Forestry University, Nanjing 210037, People's Republic of China. Electronic address: susanfang20@gmail.com.

PMID: 29777935
DOI: 10.1016/j.saa.2018.05.037

Abstract

The effect of substituted alkyl groups at different substituted position on the first excited-state proton transfer of nR7AI-H₂O (n = 2-6; R = CH₃, C₂H₅, CF₃) complexes were theoretically investigated at the TD-M06-2X/6-31 + G(d, p) level. Here n value denoted the substituted position C_n of R group. The replacement of alkyl R group had no effect on the features of HOMO and LUMO, but influenced the S₀ → S₁ adiabatic transition energies of the nR7AI-H₂O complex. Through computation, we found that the double proton transfer took place in a concerted but asynchronous protolysis pattern regardless of substituted group R and substituted position in the nR7AI-H₂O complex. The vibrational-mode specific nature of ESPT was verified. The alkyl group R changed the geometrical parameters of TS, and resulted in enlarging/narrowing the asynchronousity of ESPT. The ESPT barrier height was also affected by the substituted group and position.

Keywords: Asynchronous; Concerted; Excited-state; Proton transfer; Substituent effect.