Fluorescence Behavior of Fluorenone Derivative in Chlorinated Hydrocarbons: Verification of Solvent Proticity via Fluorescence Spectroscopy

In this study, the fluorescence (FL) behavior of a fluorenone derivative (FDMFA) in four chlorinated hydrocarbon solvents was investigated. While all four solvents have low polarities, their proticities are considerably different. Therefore, the FL properties of FDMFA could be considered to depend solely on the solvent’s proticity, with any polarity effects being insignificant. The hydrogen bond donor acidity was used as a measure of proticity, with higher values representing greater FL quenching due to vibronic coupling. The hydrogen bonding between FDMFA and the solvents could be thermodynamically controlled; thus, the FL emission was substantially enhanced during the heating process and quenched again during the cooling process. This change occurred reversibly and repeatedly. Because chlorinated hydrocarbon solvents are widely used for reaction and cleaning purposes in industrial applications, the findings of this study will be helpful in ensuring that such solvents are appropriately handled.