In the Communication (e22854), Mark G. Humphrey and co-workers report 5,15-bis(organic/organometallic)-substituted porphyrins that display outstanding two-, three-, and four-photon absorption, and that comprise a new class of molecule exhibiting five-photon absorption at wavelengths extending past 2000 nm. This research highlights the potential of porphyrins in biological applications exploiting multi-photon absorption in the near-infrared III region and beyond.
Wang et al. (Mon,) studied this question.