Synthesis, Characterization, and Dual Functional Properties of Coumarin-Based Hybrids for Biological and Optical Applications

Heterocyclic compounds incorporating nuclei of coumarin, benzimidazole, and benzothiazole exhibit significant biological and pharmacological properties. This study presents an efficient synthetic route for hybrid molecules integrating coumarin with either benzimidazole or benzothiazole under mild reaction conditions. The antibacterial and antioxidant properties of the synthesized compounds were systematically evaluated. The methodology successfully yielded 11 compounds in total, including six substituted coumarin–benzimidazole and five coumarin–benzothiazole derivatives, with yields ranging from 14 to 60%. Notably, derivatives 19 and 26 exhibited moderate antibacterial activity against Staphylococcus aureus at concentrations of 500 and 250 μg·mL–1, respectively. Derivatives 26 and 33 demonstrated strong antioxidant activity, with DPPH radical scavenging rates between 89 and 72%. Structure–activity relationship analysis revealed that substituents at position 7 of the coumarin nucleus significantly enhance antioxidant activity. Density functional theory calculations were performed to evaluate the compounds. Multivariate statistical methods, such as principal component analysis, identified molecular volume and bond order as key determinants of biological activity. Additionally, optical properties were explored, revealing promising photoluminescence characteristics with emission ranging from 446 to 502 nm. These findings suggest potential applications in theranostics and optoelectronics. This work highlights the importance of structural modifications in optimizing the biological and optical properties of coumarin-based hybrids, providing a foundation for future studies aimed at expanding their biomedical and technological applications.