Substituent Effects on the N-H Bond Dissociation Enthalpies, Ionization Energies, Acidities, and Radical Scavenging Behavior of 3,7-Disubstituted Phenoxazines and 3,7-Disubstituted Phenothiazines

Pham Thi Thu Thao; Binh Thuc Tran; Nguyen Minh Thong; Duong Tuan Quang; Nguyen Khoa Hien; Minh Tho Nguyen; Pham Cam Nam

doi:10.1021/acsomega.0c04144

Substituent Effects on the N-H Bond Dissociation Enthalpies, Ionization Energies, Acidities, and Radical Scavenging Behavior of 3,7-Disubstituted Phenoxazines and 3,7-Disubstituted Phenothiazines

ACS Omega. 2020 Oct 14;5(42):27572-27581. doi: 10.1021/acsomega.0c04144. eCollection 2020 Oct 27.

Authors

Pham Thi Thu Thao^{1

2

3}, Binh Thuc Tran², Nguyen Minh Thong⁴, Duong Tuan Quang⁵, Nguyen Khoa Hien⁶, Minh Tho Nguyen^{7

8}, Pham Cam Nam¹

Affiliations

¹ Department of Chemistry, The University of Da Nang-University of Science and Technology, Da Nang 550000, Vietnam.
² Department of Chemistry, University of Sciences, Hue University, Hue 530000, Vietnam.
³ Le Quy Don Gifted High School Quang Tri, Dong Ha, Quang Tri 520000, Vietnam.
⁴ The University of Da Nang-Campus in Kontum, Kontum 580000, Vietnam.
⁵ University of Education, Hue University, Hue 530000, Vietnam.
⁶ Mientrung Institute for Scientific Research, Vietnam Academy of Science and Technology, Hue 530000, Vietnam.
⁷ Institute for Computational Science and Technology (ICST), Ho Chi Minh City 700000, Vietnam.
⁸ Department of Chemistry, KU Leuven, Leuven 3001, Belgium.

Abstract

The substituent effects on the N-H bond dissociation enthalpies (BDE), ionization energies (IE), acidities (proton affinity, PA), and radical scavenging behavior of 3,7-disubstituted phenoxazines (PhozNHs) and 3,7-disubstituted phenothiazines (PhtzNHs) were determined using density functional theory, with the M05-2X functional in conjunction with the 6-311++G(d,p) basis set. These thermochemical parameters calculated in both gas phase and benzene solution with respect to the changes in several different substituents including halogen, electron-withdrawing, and electron-donating groups at both 3 and 7 positions in both PhozNHs and PhtzNHs systems were analyzed in terms of the inherent relationships between them with some quantitative substituent effect parameters. The kinetic rate constants of hydrogen-atom exchange reactions between PhozNH and PhtzNH derivatives with the HOO^• radical were also calculated, and the effects of the substituents on the kinetic behaviors of these reactions were thereby quantitatively evaluated.