Synthesis and Photophysics of Ambipolar Fluoren-9-ylidene Malononitrile Derivatives

The efficient synthesis of ambipolar 2,7- and 3,6-disubstituted fluoren-9-ylidene malononitrile derivatives (4 and 9) is described. Structure-activity relationships depend on the position of substitution. Population of the S-1 excited state in the 2,7-disubstituted FM derivatives is achieved via higher states, as evidenced from the UV-vis absorption and emission spectra. The results are supported by TDDFT calculations. Charge transfer states were the main deactivation path of the excited states of ambipolar 9b in polar solvents, as evidenced by fluorescence spectroscopy