Photophysical and Computational Analysis of a Symmetrical Fluorene-Based Janus Dione Derivative

Molecular symmetry plays an important role in the physical characteristics and spectra of a molecule. However, experimental results can sometimes be counterintuitive due to unpredictable properties of a molecule. Photophysical characterization of a centrosymmetrical indacene-1,3,5,7(2H,6H)-tetraone, or Janus dione, derivative revealed a two-photon absorption maximum closely associated with the main linear absorption band (a typically two-photon forbidden transition for molecules of high symmetry). Though observed previously in similar compounds, little explanation has been offered for this anomaly. Our investigation of a symmetrical Janus dione, including linear and nonlinear photophysical characterization along with TD-DFT calculations, provides insight regarding the origin of this phenomenon.