Bichromophoric Pyrazoline Derivative with Solvent-Selective Photoluminescence Quenching

The quenching of fluorescence in the presence of chloromethanes, which is an unprecedented effect for pyrazolines, has been evidenced for the first time in the case of 1,3-diphenyl-5-{4-[(4-vinylbenzyl)oxy]phenyl}-4,5-dihydropyrazole. The detailed synthesis of this aryl trisubstituted pyrazoline that combines two chromophoric units in a non-conjugated manner is presented. The compound has been extensively characterized from a structural point of view, and its crystal structure has been determined by single crystal X-ray crystallography. The fluorescence study has evidenced the particular behavior of this pyrazoline derivative in solutions of chloromethanes, and the insight gained from the experimental data has been useful in elaborating a plausible fluorescence quenching mechanism. The investigated compound was modeled by Density Functional Theory (DFT) to point out the particularities of the electron transitions in gas phase as well as in the implicit solvents. Also, the HOMO-LUMO energy gap, mapped electrostatic potential, electronic density, dipole moment and polarizability have been reported for the pyrazoline derivative.