New two-photon absorbing fluorene derivatives: Synthesis and nonlinear optical characterization

Efficient Pd-catalyzed Heck coupling methodology was employed to provide two new fluorene derivatives with phosphonate (2) and nitro (3) electron-withdrawing functionalities. Both derivatives exhibit two-photon absorption (2PA), as determined by nonlinear absorption measurements using a femtosecond pump/white light continuum probe NLO spectrometer . Both fluorene derivatives have high 2PA cross sections (650 and 1300 x 10(-50) cm(4) s photon(-1) molecule(-1) for compounds 2 and 3, respectively)