Exploring ESIPT Dynamics, Aggregation, and Sensing Applications in Novel Naphthalene-Based Aroylhydrazone Luminophores Functionalized with Electron Donating and Withdrawing Groups

Excited-State Intramolecular Proton Transfer (ESIPT) luminophores exhibit unique photophysical properties for sensing and optoelectronics. This study examines naphthalene-based aroylhydrazone derivatives (NBH-NH2 and NBH-F) to understand the impact of electron-donating (-NH₂) and electron-withdrawing (-F) groups on ESIPT dynamics. Single-crystal X-ray diffraction (SCXRD) reveals differences in molecular packing and rigidity, while UV-vis absorption, fluorescence, and excitation-dependent emission studies demonstrate the observable difference in photophysical behavior. Notably, the substituent effects are profound in different DMF/Water percentages, with NBH-NH2 showing Aggregation-Induced Emission (AIE) and NBH-F displaying Aggregation-Caused Quenching (ACQ). Time-dependent density functional theory (TD-DFT) calculations provide insights into electronic structure variations during the ESIPT process. Notably, NBH-NH2 exhibits strong fluorescence and amine-induced spectral shifts, enabling real-time biogenic amine sensing for food spoilage detection. These findings establish a structure-property relationship, offering design principles for ESIPT-based materials in fluorescence sensing, optoelectronics, and food safety applications.