Design and synthesis of coumarin-based pyrazole–pyrazoline hybrid derivatives and their photophysical, antimicrobial, sensing and computational studies

Abstract

In recent times, nitrogen-containing multi-heterocyclic compounds have emerged as valuable scaffolds in the field of medication development because of their broad spectrum of biological activities. In this context, we designed and synthesized new multi-heterocyclic coumarin-based pyrazole–pyrazoline hybrids (4a–4r) through a molecular hybridization approach. The green metrics assessment results revealed that the current molecular hybridization approach is environmentally benign and provides excellent green certification for a safe and sustainable environment. After successful structural characterization, all compounds were evaluated for their antimicrobial potential against various microbial strains. The results of antimicrobial studies showed that compound 4c was most active against B. subtilis and A. niger, with MICs of 0.0132 and 0.0265 µmol mL⁻¹, respectively. To understand the plausible mechanism responsible for the antimicrobial action of the synthesized compounds, molecular docking studies were performed. Furthermore, the sensing behaviours of multi-heterocyclic molecules (4a–4r) were evaluated, and the results revealed that most of the derivatives detected Cu²⁺, Ce⁴⁺ and Hg²⁺ metal ions in nanomolar detection limits. The Job's and B–H plots demonstrated that these compounds interact with Cu²⁺, Ce⁴⁺ and Hg²⁺ ions in ratios of 1 : 1, 1 : 2 and 2 : 1 binding stoichiometry, respectively.