Theoretical investigation and reconsideration of intramolecular proton-transfer-induced the twisted charge-transfer for the fluorescent sensor to detect the aluminum ion

A Schiff base compound 6-amino-5-(((2-hydroxynaphthalen-1-yl)methylene)amino)-2-mercaptopyrimidin-4-ol (AHM) in acetonitrile solvent is found to show “OFF–ON type” mode upon addition of Al3+ ion and successfully applied for selective recognition ion. In this work, the reconsideration excited state intramolecular proton transfer (ESIPT) twisted charge (TICT) has been explored detail based on density functional theory (DFT) time-dependent (TD-DFT) methods. absence Al3+, lone pair electrons are transferred from –C = N –OH forming a hydrogen-bonding configuration, AHM shows weak fluorescence. When coordinated with metal ion, TICT eliminated, emission significantly enhanced. Thus, paper, origination non-emissive behavior explained detail. The frontier molecular orbitals (MOs) hole-electrons used analyze distribution, providing strong evidence possibility ESIPT processes occurring.