Synthesis, Characterization, and Biological Evaluation of Schiff Bases Incorporating Pyridine and Pyrazole Units Using Sustainable Solvents

Aza-heterocyclic frameworks are highly valued for their potential therapeutic benefits and utility as versatile synthetic building blocks. Pyrazole and pyridine are key heterocyclic compounds with a wide range of applications across pharmaceutical chemistry, polymer science, agrochemicals, materials science, and other fields. This study focuses on the sustainable synthesis of (Z)-N′-(1,3-diphenyl-1H-pyrazol-4-yl)methylidene­pyridine-4-carbohydrazide derivatives, which have shown significant potential due to their diverse biological activities, particularly antimicrobial properties. Traditional synthesis of pyrazole- and pyridine-containing heterocycles often relies on harsh conditions such as organic solvents, high temperatures, and long reaction times, leading to higher energy consumption and costs. This work focuses on greener methodologies as viable alternatives that align with sustainability principles. The target compounds were successfully synthesized using polyethylene glycol (PEG-400) as the most efficient solvent. The synthesized compounds were evaluated for their antimicrobial activity against a range of bacterial and fungal strains.