Synthesis of π-expanded BODIPYs and their fluorescent properties in the visible-near-infrared region

A series of pi-expanded boron-dipyrromethenes (BODIPYs) fused with aromatic rings at beta,beta-positions, such as benzene, acenaphthylene, and benzofluoranthene were prepared by the reaction of BF(3)center dot OEt(2) with bicyclo[2.2.2]octadiene-fused dipyrromethene and the subsequent retro Diels-Alder reaction. These BODIPYs exhibited the absorptions and the fluorescence emissions over wide range of visible-near infrared region at 500-800 nm. BODIPYs composed of two fluorantho[8,9-f]isoindoles absorbed and emitted at red-region over 750 nm with absolute fluorescence quantum yield (Phi(f)) of ca. 0.3, although they are unstable under air in room light. BODIPY composed fluorantho[8,9-f]isoindole and acenaphtho [1,2-c]pyrrole was stable and showed a bright fluorescence emission at 695 nm with high Phi(f) of 0.70. (C) 2010 Elsevier Ltd. All rights reserved.