Switching High Two-Photon Efficiency: From 3,8,13-Substituted Triindole Derivatives to Their 2,7,12-Isomers

Bridging the triindole core and triarylboryl acceptor by an ethenylene linker at the 3,8,13- or 2,7,12-position, the resultant 3-BET and 2-BET show two-photon absorption (TPA) cross sections of delta = 2100 and 2500 GM (at 810 nm by femtosecond pulses in THF), respectively. The TPA enhancement of the 2,7,12-isomers is also found when comparing 3-BYT and 2-BYT (delta = 870 and 1900 GM) and 3-NET and 2-NET (36 and 400 GM).