Formation of Novel Coumarin-Based Hydrazone Derivatives for chromogenic chemosensors

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The development of optically active molecular receptors capable of selective and distinct recognition of biochemically and environmentally crucial analytes represents a vital focus in supramolecular chemistry. Zinc (Zn2+) is the second most abundant essential trace element in biological systems, governing critical cellular signaling pathways, enzymatic catalysis, gene expression, and neurophysiological functions. In this study, a facile and efficient synthetic protocol is established for a series of coumarin-hydrazone conjugates designed as fluorogenic and chromogenic chemosensors. The synthetic route proceeds via esterification of coumarin-3-carboxylic acid, hydrazinolysis to yield coumarin-3-carbohydrazide with high isolated yield (>90\%), followed by acid-catalyzed Schiff base condensation with targeted aromatic aldehydes, including 2-chlorobenzaldehyde, 2,4-dichlorobenzaldehyde, and substituted salicylaldehydes. This modular approach provides functionalized conjugated scaffolds optimized for selective coordination and fluorometric detection of transition metal ions.