Theoretical study on the substituent effect of halogen atom at different position of 7-azaindole-water derivatives: relative stability and excited-state proton-transfer mechanism

• Published in: Structural chemistry 2018-10, Vol.29 (5), p.1341-1350
• Main Authors: Yi, Jiacheng, Fang, Hua
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Computer Applications in Chemistry; Mathematical analysis; Molecular orbitals; Molecular structure; Original Research; Physical Chemistry; Protons; Substitutes; Theoretical and Computational Chemistry; Water chemistry
• ISSN: 1040-0400; 1572-9001
• DOI: 10.1007/s11224-018-1119-z

We have theoretically investigated the substituted effect on the first excited-state proton-transfer process of nX 7AI-H 2 O ( n  = 2~6, X  = F, Cl, Br) complex at the TD-M06-2X/6-31 + G(d, p) level. Here X is the substituted halogen atom, and n value denotes the substituted position of X , such as C 2 , C 3 , C 4 , C 5 , or C 6 . For the substituted 7-azaindole clusters, 6 X 7AI-H 2 O molecule is the most stable structure in water. The replacement of halogen atom X does not affect the characters of the HOMO and LUMO, but influence the S 0  → S 1 adiabatic transition energies of nX 7AI-H 2 O ( n  = 2~6, X  = F, Cl, Br). Our calculated results show that the double proton transfer occurs in a concerted but asynchronous protolysis pathway no matter which H atom is replaced by halogen atom. The halogen substitution changes the structural parameters evidently and leads to amply the asynchronousity during the proton-transfer process. The ESPT barrier height increases or decreases due to the halogen atom and substituted position.