Fluorene-Based Organic Molecule with High Two-Photon Absorption Activities

Abstract High two-photon absorption (TPA) molecule having a fluorene π-center (TP-Flu-TP) was prepared by the Heck reaction of 2,7-dibromo-9,9-diethylhexyl-9H-fluorene and 4-(diphenylamino)benzstyrene. The linear absorption maximum of the TP-Flu-TP was observed at 410 nm. The dispersion of the TPA intensity for the chromophore was measured by nonlinear transmission using 7 ns laser pulse. Since the maximum wavelength of this molecule occurred at 740 nm, we fixed the pumping wavelength at 740 nm for TP-Flu-TP and measured the transmitted pulse energy versus the input pulse energy. From this experiment we observed a distinct nonlinearity from TP-Flu-TP demonstrating that it is a potential material for optical limiting. The calculated two-photon absorption cross section (Δ) by the Hartree-Fock Hamiltonian with single configuration interaction formalism was 1.37 × 10−47 cm4 sec/photon.