Synthesis and characterization of two-photon chromophores based on a tetrasubstituted tetraethynylethylene scaffold

A new series of model dye molecules composed of three multibranched analogues based on the tetrasubstituted tetraethynylethylene structural motif have been synthesized and experimentally shown to possess strong and widely dispersed two-photon absorption (2PA) in the near-IR region. It was found that the spectral position of the major 2PA band could be tuned by the electronic nature of the selected substitution units. The studied model fluorophores also exhibited fairly low photodegradation of their fluorescence intensity even under prolonged UV-light irradiation, which is beneficial for the development of fluorescence probes that are needed for long-term light exposure. Furthermore, representative chromophores were selected to demonstrate the power-control properties within the femtosecond and nanosecond time domains. Two is better than one: Multibranched chromophores based on the tetrasubstituted ethynylethylene skeleton with functionalized quinoxalinoids as aryl substituents are synthesized and shown to possess strong and widely dispersed two-photon absorption in the near-IR region. This molecular archetype is also demonstrated to possess optical power-limiting properties and optical power-stabilization properties toward laser pulses in various time domains.