Agradecimentos: This research was funded by the São Paulo Research Foundation (FAPESP) under the grants 2014/06451-7 (T. A. S. C. and L. A. P.) and 2013/16911-2 (L. W. T. B., T. A. S. C. and L. A. P.), the Brazilian Funding Agency – CNPq (L. W. T. B., T. A. S. C., C. H. B. C. and L. A. P.), and the Deutsche Forschungsgemeinschaft within SFB 1176 (project Q4 of A. B., project A4 of S. B.). We thank Wim Klopper (Karlsruhe Institute of Technology) for valuable discussions concerning the quadratic response calculations. For additional support, we are grateful to the Karlsruhe School of Optics & Photonics (D. K. K. and A. H.), the Carl Zeiss Foundation (A. H.) and the Karlsruhe House of Young Scientists (A. H.) Ver menos

We report on the two-photon absorption spectra of a series of 2,6-disubstituted BODIPY dyes. Depending on the substituents, we observe increasing two-photon absorption cross sections with values up to 350 GM compared to 70 GM in the unsubstituted dye. Quantum chemical calculations are performed to assign the absorption bands and to understand the factors controlling the size of the two-photon absorption cross section. Both the maximum of the two-photon absorption band as well as the red- shift of the whole spectrum correlate with the ability of the substituents to extend the pi-electron system of the dye. The above-mentioned intense two-photon absorption band corresponds to the absorption of photons with 1.3 eV, which is at the first near-infrared transparency window for biological tissues. The dyes could thus be suitable for bio-imaging applications. Ver menos