Quantum Yield Switching of Fluorescence by Selectively Bridging Single and Double Bonds in Chalcones: Involvement of Two Different Types of Conical Intersections

Abstract

From the fluorescence properties of chalcones as a function of solvent polarity, and by the comparison to derivatives with donors and acceptors and with various selectively bridged bonds, it can be concluded that two emissive and two nonemissive states are needed to describe the fluorescence behavior. Three of these states are connected with bond twisting and lead to species with high or low dipole moment, two of them situated in the proximity of a conical intersection.