Experimental and theoretical insights into free radical capturing activity of 1,5-diaminonaphthalene and 1,5-dihydroxynaphthalene

•DHN is a better DPPH• free radical scavenger than DAN and Trolox.•DAN is more effective at neutralizing ABTS•+ radical cations than DHN and Trolox.•DAN and DHN react with HOO• free radicals mainly via HAT mechanism.•HAT product amount constitutes over 92% of the total products. The radical scavenging activity of two naphthalene derivatives, 1,5-diaminonaphthalene (DAN) and 1,5-diaminonaphthalene (DAN) and 1,5-dihydroxynaphthalene (DHN), was investigated through both experimental and density functional theory methods. Experimentally, the antioxidant capacity of these compounds was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH·) assay and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS·+) assay and compared to the standard antioxidant Trolox. DHN demonstrated a superior ability to capture DPPH· free radicals, with an IC50DPPH value of 3.62 ± 0.01 µM, while DAN was more effective at neutralizing ABTS·+ radical cations, with an IC50ABTS value of 17.36 ± 0.02 µM. Theoretically, density functional theory (DFT) calculations using the theory level of ωb97xd/6–311++g(d,p) were employed to determine the thermodynamic parameters of DHN and DAN in the gas phase and ethanol solvent. Furthermore, the mechanisms and kinetics of capturing reaction between both naphthalene derivatives and HOO· radical were also investigated. Based on the potential energy surfaces (PES) via hydrogen atom transfer (HAT) and radical adduct formation (RAF) paths, HAT was determined to be the favored mechanism, with the product amount accounting for more than 99% in the gas phase and 92% in ethanol. [Display omitted]