Synthesis and two-photon property studies of symmetrically substituted bisarylacetylene structures using functionalized quinoxalinoid units as the aryl substituents

A series of symmetrically substituted multi-polar chromophores (1-3) based on the skeleton of bisarylacetylene using functionalized quinoxaline, indenoquinoxaline, and pyridopyrazine moieties as the aryl substituents has been synthesized and characterized for their two-photon absorption properties using femtosecond laser pulses as the probing tool. Under our experimental conditions, these model fluorophores are found to manifest strong and wide dispersed two-photon absorption in the near infrared (NIR) region. It is demonstrated that molecular structures with multi-branched π-frameworks incorporating functionalized quinoxalinoid units would possess large molecular nonlinear absorptivities within the studied spectral range. Optical power-limiting behavior in the femtosecond time domain of the indenoquinoxaline-derived dye molecule (2) from this model compound set was also investigated and the result indicates that such structural motif could be a useful approach for the molecular design towards strong two-photon absorbing material system for quick-responsive and broadband optical-control related applications.