Star-shaped panchromatic absorbing dyes based on a triazatruxene platform with diketopyrrolopyrrole and boron dipyrromethene substituents

The engineering of photoactive arrays built from a flat, functionalized triazatruxene (TAT) platform is described. The primary synthetic strategy involved the step by step connection of one, two or three bis(thienyl)diketopyrrolopyrrole (DPP) modules. Subsequent bromination of the pendent thiophene ring was not selective and provided a mixture of regioisomers. However, selective grafting of boron dipyrromethene (Bodipy) units via Pd-catalysed cross couplings enabled the construction of TAT/DPP/Bodipy arrays. As well, direct coupling of two green F-Bodipy units to dibromoTAT provided a substrate suitable for reaction with hydroxyl-propargyl-substituted red Bodipy dyes to give ready access to O-Bodipy linked multichromophoric systems. All the new dyes displayed strong absorption in the near-UV and visible region of the solar spectra (400–750 nm), with intramolecular cascade energy transfer enabling photon concentration and fluorescence at approximately 740 nm.