Energy- and Electron-Transfer Processes in Corrole-Perylenebisimide-Triphenylamine Array

A multichromophoric system, TPA-C-PI, possessing a corrole as the central unit linked to perylene bisimide and N-[4-(phenylethynyl)phenyl]-N,N-diphenylamine was efficiently synthesized, as were the component dyads C-PI and C-TPA. The combination of known methodologies with the newest synthetic advances in Pd-coupling reactions enabled a six-step preparation of the final compounds in a convergent fashion. Several different synthetic strategies were investigated, and one with Sonogashira coupling involved in the final step was successful. Electrochemical and spectroscopic studies confirmed a weak coupling between the component units in the triad which was characterized by an extensive absorption throughout the 300-700 nm region. Photophysical measurements showed efficient energy transfer to occur from the diphenylacetylene substituted aromatic amine (99%) and perylene bisimide unit (100%) to the corrole and subsequent electron transfer from the corrole to perylene bisimide (97% efficient). The final charge separated state in TPA-C-PI was identified as TPA-C(+)-PI(-), with a lifetime of 1.9 ns, similar to that of C(+)-PI(-) (2.3 ns). The charge separated state with charges on the extreme components, TPA(+)-C-PI(-), is not formed for thermodynamic reasons.