Dual fluorescence in donor-acceptor molecules and the effect of fluorination

Fluorescent properties of the P4CF2 and P4CF3 molecules are studied by quantum-chemical methods taking into account the interaction with a polar solvent. It is shown that the molecules exhibit two minima of the potential where hydrogen bonding with a proton-donor solvent can occur. A mechanism responsible for two-band anomalous fluorescence in para- and orthoposions is disccussed. The mechanism was earlier described in [2]. The effect of fluorine substitution in para- and orthopositions is also considered. It is found that strong hydrogen bonding takes place to give a molecule — polar solvent complex where two radiative states of different origin can occur.