Synthesis of new donor-fluorene-donor type organic dyes and their nonlinear absorption properties

We have synthesized two new donor-fluorene-donor type organic dyes (JFJ and TFT) which contain an alkyl fluorene unit bridging two donor groups. In order to enhance the two photon absorption efficiency the molecules were designed for facile donation of electrons from the substituent groups as well as for high coplanarity of the molecule. The wavelength of maximum absorption of TFT and JFJ appeared at 412 and 406 nm, respectively. The photoluminescence (PL) spectra show maximum emission wavelengths of TFT and JFJ in chloroform solution at 465 and 495 nm, respectively. From optical power limiting experiments, the nonlinear coefficients (σ2) of JFJ and TFT were found to be 8 × 10−21 and 4 × 10−21 cm4/GW, respectively.