LAUSR

Fluorescent sensors with selectivity and sensitivity to metal ions are an active field in supramolecular chemistry for biochemical, analytical, and environmental problems. Mg2+ is one of the most abundant divalent ions in the cell, and it plays a critical role in many biological processes. Coumarin‐based sensors are widely used as desirable fluorophore and binding moieties showing a remarkable sensitivity and fluorometric enhancement for Mg2+. In this work, density functional theory/multireference configuration interaction (DFT/MRCI) calculations were performed in order to understand the sensing behavior of the organic fluorescent sensor 7‐hydroxy‐4‐methyl‐8‐((2‐(pyridin‐2‐yl)hydrazono)methyl)‐2H‐chromen‐2‐one (PyHC) in ethanol to solvated Mg2+ ions. The computed optical properties reproduce well‐reported experimental data. Our results suggest that after photoexcitation of the free PyHC, a photo‐induced electron transfer (PET) mechanism may compete with the fluorescence decay to the ground state. In contrast, this PET channel is no longer available in the complex with Mg2+ making the emissive decay more efficient. © 2019 Wiley Periodicals, Inc.