Tripyrrindiones and a red-emitting fluorescent derivative

Abstract  

Orange-colored 7,8-dimethyl-2,3,12,13-tetramethoxy-(15H,17H)-tripyrrin-1,14-dione and its 2,3,7,8,12,13-hexaethyl analog were synthesized and converted to fluorescent derivatives by bridging a lactam nitrogen to the adjacent pyrrole nitrogen in a reaction with carbonyldiimidazole. The tripyrrindiones were also converted to the corresponding mono lactim methyl ethers by reaction with neat trimethylphosphite, and a corresponding difluoroboryl (BODIPY) derivative was made from the lactim by reaction with boron trifluoride etherate. X-ray structures of the tetramethoxytripyrrindione, the N,N′-carbonyl-bridged hexa-ethyltripyrrindione, and the lactim methyl ether of the hexa-ethyltripyrrindione were determined. The N,N′-bridged pigments exhibited very large Stokes’ shifts with fluorescence quantum yields ranging from 1.0 to 0.02.