Fluorene as the π-spacer for new two-photon absorption chromophores

We report herein the design and synthesis of two new quadrupolar D-pi-A-pi-D chromophores containing diphenyl amine and dicyanobenzene or 2,1,3-benzothiadiazole as electron donor (D) and acceptor (A), respectively, which are bridged by fluorene linkage (pi). The introduction of coplanar fluorenes is highly beneficial for the enhancement of two-photon absorption (TPA), where 1b displays a TPA cross section (sigma(2)) of up to 1975 +/- 207 GM. (C) 2010 Elsevier Ltd. All rights reserved.