Synthesis, Antioxidant Activity, and Structure Analysis Relationship Study of Silyl-Alkylthioetheres from 2-Mercaptobenzimidazole

Oxidative stress results from the excessive production of reactive oxygen species (ROS), which cause cellular and molecular damage and contribute to chronic diseases. Given the recognized antioxidant potential of benzimidazole derivatives—particularly 2-mercaptobenzimidazole—this study aimed to synthesize novel organosilicon S-silylalkylthioethers (I–IV) and N-alkylsilylthioethers (1a–3f) derived from this scaffold and to evaluate their antioxidant and antibrowning properties. The S-silylalkylthioethers were obtained by reacting 2-mercaptobenzimidazole with different chloroalkylsilanes under reflux in ethanol, followed by a reaction with alkyl halides in aprotic media at room temperature to prepare the N-alkylsilylthioethers. Structural elucidation was achieved through 1D and 2D NMR and FT-IR. Antioxidant activity was assessed using DPPH, the total antioxidant capacity, and ferric-reducing assays. The results showed several derivatives with notable antioxidant responses, revealing a clear relationship between carbon chain length, logP values, organosilicon substitution patterns, and radical-scavenging efficiency. Spearman correlation analysis further confirmed that DPPH activity is inversely related to total carbon number, molecular size, molecular weight, and LogP (ρ = −0.68 to −0.73, p < 0.001) and moderately negatively correlated with N-alkyl chain length (ρ = −0.47, p = 0.027), while S-alkyl chains showed no significant effect. These findings highlight the potential of these benzimidazole–organosilicon hybrids as antioxidant candidates and demonstrate how physicochemical properties govern their reactivity and antiradical capacity.