Twisted Intramolecular Charge Transfer‐Based Fluorometric Detection of D‐fructose by Boronic Acid‐Containing BF2‐β‐Diketonate Complexes

Abstract Novel BF 2 ‐β‐diketonate complexes 1 – 4 bearing phenylboronic acid moieties and methoxyphenyl or dimethylaminophenyl groups were synthesized and their photophysical properties, pH response, and reactivity to D‐fructose were evaluated. Complexes 1 and 2 bearing a methoxyphenyl group luminesced with high intensity in a range of non‐polar to polar solvents, except in DMSO, whereas complexes 3 and 4 containing a dimethylaminophenyl group with twisted intramolecular charge transfer (TICT) properties showed a dramatic decrease in luminescence intensity with increasing solvent polarity. The luminescence intensity of complexes 1 and 2 decreased with increasing pH due to intermolecular vibration which associated with hydrogen bonding between the complexes and solvent water molecules, whereas it increased when they reacted with D‐fructose due to the suppression of the intermolecular vibration. In contrast, the luminescence intensity of complexes 3 and 4 increased with increasing pH and upon reaction with D‐fructose due to the loss of its TICT properties. The photophysical properties of complexes 1 – 4 and the TICT properties of complexes 3 and 4 were supported by density functional theory calculations.