A comparative DFT study on antioxidative activity of 3- and 4-phenylcoumarins: an aspect of structure, electronics, mechanism, kinetics, and metal chelate relations

• Published in: Structural chemistry Vol. 35; no. 1; pp. 265 - 275
• Main Authors: Thuy, Phan Thi, Duc, Dau Xuan, Son, Ninh The
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-02-2024; Springer Nature B.V
• Subjects: Benzene; Chemistry; Chemistry and Materials Science; Computer Applications in Chemistry; Density functional theory; Hydrocarbons; Hydroxyl groups; Methanol; Nitrogen dioxide; Physical Chemistry; Theoretical and Computational Chemistry; Density functional theory; Hydroxy group; Antioxidant; Comparison; Coumarin
• ISSN: 1040-0400; 1572-9001
• DOI: 10.1007/s11224-023-02183-3

The current study aims to compare antioxidative activity of 3-phenylcoumarin 7-dihydroxy-3-(3′,4′-dihydroxyphenyl)chromenone (1) and 4-phenylcoumarin 6,7-dihydroxy-4-(3′,4′-dihydroxyphenyl)chromenone (2) by a DFT (density functional theory) calculation. Thermodynamic and kinetic actions of two studied coumarins 1–2 were considered at the M06-2X/6–311++G(d,p), in which their antiradical activity is due to hydroxy bond breaking. The HAT mechanism is essential for two compounds in gas and benzene, but the SPL-ET mechanism is a principal route in methanol and water. Hydroxy groups at C-6 and C-4′ of both two compounds, on the one hand, have induced the lowest BDE values of 76.8–79.6 kcal/mol in gas and benzene, and the lowest PA values of 37.4–40.8 kcal/mol in methanol and water, on the other hand, are the best groups the kinetic reactions with HOO
•
and
•
NO
2
radicals. 1–6-OH shows the best acidity with the lowest pK
a
value of 8.65. Phenyl hydroxyl groups of compound 1 have chelations to Fe
2+
, to form the most stable complex with the lowest IE value of −189.6 kcal/mol, and the highest MIA value of 284.7 kcal/mol. In general, the antioxidative activity of 3-phenylcoumarin 1 is better than that of 4-phenylcoumarin 2.