Step-by-Step Synthesis of Multimodule Assemblies Engineered from BODIPY, DPP, and Triphenylamine Moieties.

In the present account we describe unsymmetrical triads constructed from extended borondipyrromethene (BODIPY) dyes, diketopyrrolopyrrole (DPP) dyes, and electron donor fragments based on triarylamine. The assemblages are such that each module maintains its individual optical and redox properties. The use of phenyl-alkyne-phenyl or phenyl-alkyne-thienyl spacer units is favorable for weak electronic interaction between the modules. The step-by-step linking of each module using palladium-catalyzed cross-coupling reactions provides both mono- and disubstituted derivatives, the latter obtained by passing in particular through a pivotal monosubstituted DPP building block with a reactive bromo substituent. Thus, grafting of a second dye occurs in a controlled manner, providing the target triads in good yields. This protocol allows also the synthesis of key intermediates and dyads, which appear useful for the understanding of the electrochemical and spectroscopic properties. All the dyes exhibit redox and optical properties suitable for cascade energy transfer and photoinduced electron transfer processes in appropriate solvents.