Synthesis and two-photon absorption property characterizations of small dendritic chromophores containing functionalized quinoxaliniod heterocycles.

A series of star-shaped multi-polar chromophores (compounds 1-3) containing functionalized quinoxaline and quinoxalinoid (indenoquinoxaline and pyridopyrazine) units has been synthesized and characterized for their two-photon absorption (2PA) properties both in the femtosecond and the nanosecond time domain. Under our experimental conditions, these model fluorophores are found to manifest strong and wide-dispersed two-photon absorption in the near-infrared region. It is demonstrated that molecular structures with multi-branched π frameworks incorporating properly functionalized quinoxalinoid units would possess large molecular nonlinear absorptivities within the studied spectral range. Effective optical-power attenuation and stabilization behaviors in the nanosecond time domain of a selected representative dye molecule (i.e., compound 2) from this model compound set were also investigated and the results indicate that such structural motif could be a useful approach for the molecular design toward strong two-photon-absorbing material systems for quick-responsive and broadband optical-suppressing-related applications, particularly to confront long laser pulses.