2-Bromo perylene diimide: synthesis using C–H activation and use in the synthesis of bis(perylene diimide)–donor electron-transport materials

2-Bromo-N,N′-bis(2-octyldodecyl)perylene-3,4:9,10-bis(dicarboximide) (2-bromo-PDI) can be synthesised in high yield from the parent PDI by transition-metal catalysed borylation, followed by treatment with copper(II) bromide. Stille coupling with distannyl derivatives of bithiophene, dithieno[3,2-b:2′,3′-d]thiophene, and 4-hexyl-4H-dithieno[3,2-b:2′,3′-d]pyrrole afforded three PDI–donor–PDI triads. The triads exhibit reversible reductions at similar potential to the parent PDI, and bridge-based oxidations. The absorption spectra of the triads shows a visible PDI-based transition – the structure of which suggests considerably more planar PDI units than observed for an analogous triad based on linkage through the PDI 1-position – and a lower energy transition attributed to bridge-to-PDI charge transfer. The bithiophene- and dithienothiophene-bridged triads have been used as electron-transport materials in n-channel organic field-effect transistors (the former as a 1 : 1 blend with polystyrene) and exhibit average field-effect mobility values of 0.024 and 0.013 cm2 V−1 s−1, respectively.