A Diradical Approach towards BODIPY-Based Dyes with Intense Near-Infrared Absorption around lambda=1100 nm

Abstract

A diradical approach to obtain stable organic dyes with intense absorption around lambda= 1100 nm is reported. The para- and meta-quinodimethane-bridged BODIPY dimers BD-1 and BD-2 were synthesized and were found to have a small amount of diradical character. These molecules exhibited very intense absorption at lambda= 1088 nm (epsilon= 6.65 x 10(5) m(-1)cm(-1)) and 1136 nm (epsilon= 6.44 x 10(5) m(-1)cm(-1)), respectively, together with large two-photon-absorption cross-sections. Structural isomerization induced little variation in their diradical character but distinctive differences in their physical properties. Moreover, the compounds showed a selective fluorescence turn-on response in the presence of the hydroxyl radical but not with other reactive oxygen species.