Features of the electronic structure of excited quadrupolar molecules in non-polar solvents

Interactions of the electronic subsystem of the quadrupolar fluorophore with intramolecular high-frequency antisymmetric vibrations and solvent polarization are responsible for charge transfer symmetry breaking (SB), which is observed after optical excitation of such molecules in polar solvents. It is known that although these two interactions are mathematically described in similar ways, only the interaction of the fluorophore with solvent orientational polarization can create a state with broken symmetry if this interaction is strong enough. Nevertheless, the interaction of a quadrupolar fluorophore with intramolecular high-frequency antisymmetric vibrations in non-polar solvents leads to a considerable reconstruction of the electronic subsystem. The analysis of the excited state of quadrupolar molecules in non-polar solvents performed in this study reveals that such molecules can behave like quantum two-state systems, that is, as a quasi-spin $s=1/2$, having an electric dipole moment instead of a magnetic one. This feature of excited quadrupolar molecules may be of interest to emerging technologies of molecular electronics.