Degenerate two-photon absorption and effective optical-power-limiting properties of multipolar chromophores derived from 2,3,8-trisubstituted indenoquinoxaline

Two analogous multipolar chromophores (1 and 2) that contained 2,3,8-trisubstituted indenoquinoxaline moieties have been synthesized and characterized for their two-photon absorption properties, both in the femtosecond and nanosecond time regimes. We demonstrated that their multi-branched framework structures, which incorporated appropriately functionalized indenoquinoxaline units, afforded large molecular nonlinear absorptivities within the studied spectroscopic range. Effective optical-power-limiting and stabilization behaviors in the nanosecond regime of dye molecule (2) were also investigated and the results indicated that such a structural motif could be a useful approach to the molecular design of highly active two-photon systems for quick-response and related broadband optical-suppressing applications, in particular for confronting laser pulses of a long duration. In pole position: Two multipolar chromophores that were derived from 2,3,8-functionalized indenoquinoxaline units manifest strong and wide dispersed two-photon absorption (2PA) in the NIR region under the irradiation of femtosecond laser pulses. Moreover, these model fluorophores could act as effective power-limiters/stabilizers against nanosecond laser pulses within the same spectroscopic regime.