Adaptable DNA-Interactive Probe Proficient at Selective Turn-On Sensing for Al³⁺: Insight from the Crystal Structure, Photophysical Studies, and Molecular Logic Gate

The synthesized Schiff base ligand 3-hydroxy-N′-(2-hydroxy-3-methoxybenzylidene)-2-naphthohydrazide (H₂NPV) is structurally characterized by single-crystal X-ray diffraction (XRD) and exhibits weak fluorescence in the excited state owing to the effect of excited-state-induced proton transfer (ESIPT). However, in the presence of Al³⁺, the ESIPT is blocked and chelation-enhanced fluorescence (CHEF) is induced because of complexation with the cations, resulting in turn-on emission for Al³⁺. The probe H₂NPV selectively detects Al³⁺ among the various metal ions, and the detection limit is found to be 1.70 μM. The composition and modes of complex coordination were determined by spectroscopic, theoretical studies and molecular logic gate applications. Finally, DNA binding studies were performed by spectroscopic and calorimetric methods to elucidate possible bioactivity of H₂NPV.