Synthesis and Photophysical Properties of Donor- and Acceptor-Substituted 1,7-Bis(arylalkynyl)perylene-3,4:9,10-bis(dicarboximide)s

A series of 1,7-bis(arylethynylt)-N,N'-bis[2,6-diisopi-opylphenyl]perylene-3,4:9,10-bis(dicarboximide)s has been obtained from Sonogashira coupling of the 1,7-dibromoperylene-3,4:9,10-bis(dicarboximide) with p-substituted phenylacetylenes in which the p-substituents include pi-donors (dialkylamino, diarylamino, p-(diarylamino)phenyl, alkoxy) and pi-acceptors (diarylboryl, p-(diarylboryl)phenyl). The bis(arylethynyl)-substituted chromophores all show two reversible molecular reductions and are all slightly more readily reduced than unsubstituted perylene-3,4:9, 10-bis(dicarboximide)s with the electrochemical potentials being rather insensitive to the pi-donor or acceptor nature of the aryl group. The amine derivatives also show reversible molecular oxidations. The UV-vis spectra of the chromophores with alkoxy and boryl substituents show red-shifted absorptions relative to unsubstituted perylene diimides with discernible vibronic Structure. In contrast. the lowest energy absorptions of the amino derivatives are broad and Structure less, suggesting donor-to-acceptor charge-transfer character. Transient absorption spectra for the amine derivatives were interpreted ill terms of ultrafast charge separation, followed by charge recombination oil a time scale of ca. 80-2000 ps. Two compounds were also synthesized ill which an additional stronger, but More weakly Coupled, donor group is linked by a nonconjugated bridge to the p-amine donor, to investigate the effect on the charge recombination lifetimes; however, the lifetimes of the charge-separated states. ca. 150 and 1000 ps, were within the range observed for the simple amine systems. Finally, the two-photon absorption properties of three bis(arylethynyl)Substituted derivatives were investigated, along with those of 1,7-di(pyrrolidin-1-yl)-N,N'-bis[2,6-diisopropylphenyl]perylene-3,4:9,10-bis(dicarboximide). As with other perylene-3,4:9,10-bis(dicarboxiimide)s and related species, strong two-photon absorption (> 1000 GM) was observed for three of these species close to the one-photon absorption edge; however. an additional feature (100-500 GM) was also observed at longer wavelength. An example with (p-aminophenyl)ethylnyl substituents showed a qualitatively different two-photon spectrum with a cross-section >500 GM being observed over a broad wavelength range.