Two-photon absorption and effective optical power-limiting properties of small dendritic chromophores derived from functionalized fluorene/oxadiazole units

A set of novel multi-branched chromophores composed of four analogues with generic skeletons of donor-π-acceptor (D-π-A) derived from functionalized fluorene/oxadiazole moieties has been synthesized and experimentally shown to possess strong and wide-dispersed two-photon absorptivities in near infrared (NIR) region under the irradiation of femtosecond laser pulses. It is demonstrated that structural parameters, such as the size of π-framework and the number of electron-donating units attached are closely connected to the molecular two-photon activities of these model compounds. Effective optical power-attenuation behaviors in the nanosecond time domain of the studied chromophores were also investigated and the results indicate that such dye molecules can be potential materials as broadband and quick-responsive optical-limiters especially against those laser lights with longer pulses.