Synthetic Routes to Core-fluorinated Perylene Bisimide Dyes and their Properties

Abstract

Numerous core-fluorinated perylene bisimide (PBI) dyes with various substituents at the imide positions have been synthesized by different methods. Core-difluorinated PBIs 4a-f are obtained by imidization of difluoro-substituted perylene bisanhydride 1 with appropriate primary amines or, alternatively, by nucleophilic halogen exchange reactions (Halex process) of the corresponding dibromosubstituted PBIs 2a-d,f with potassium fluoride. Core-tetrafluorinated PBIs 5a-c could also be synthesized by halogen exchange reactions of the respective tetrachlorinated PBIs 3a-c. In particular, core-fluorinated perylene bisimide pigments 4h, 5h containing hydrogen atoms in the imide positions could be obtained for the first time by deprotection of α-methylbenzyl-substituted precursors. Compared with core-unsubstituted perylene bisimides, these fluorinated dyes display hypsochromically shifted absorption and fluorescence spectra, and they exhibit fluorescence quantum yields up to unity, enabling bright yellow emission. The electrochemical properties of these electron-poor perylene bisimides have been studied. Furthermore, the packing features of a tetrafluorinated PBI derivative in the solid state have been discussed.

Semiconducting Self‐Assembled Nanofibers Prepared from Photostable Octafluorinated Bisanthene Derivatives

“…In contrast, the cyclic voltammograms of the compounds exhibit reversible reduction waves but the differences in the values of the first reduction potentials ( E red 1 ) were smaller than those of E ox 1 values ( E red 1 =−1.24 V for F8 vs. −1.32 V for F4 vs. −1.33 V for F0 ). This implies that fluorine substitution at this region affects the compounds’ HOMO rather than the lowest unoccupied molecular orbital (LUMO) as seen in fluorinated perylene bisimide dyes, whereas large effects of fluorination on the LUMO of linear acene derivatives have also been reported . Note that the steric and electronic effects of substitutions at the meso ‐position were reported to affect both HOMO and LUMO levels of the compounds .…”

Perylene Bisimide Dye Assemblies as Archetype Functional Supramolecular Materials

“…Further calculations show that as soon as one or more substituents are introduced in bay positions, the lowest energy conformation exhibits two rotationally displaced naphthalene imide subunits. 15,64 Other contortions of the PBI scaffold have been observed occasionally as well in single crystals, 65 but it appears that the PBI waistline, in simple view consisting of two naphthalene imide subunits connected by single sp 2 hybridized carbon−carbon bonds (bond length of 1.46 Å), is most easily distorted by a propeller-type contortion to accommodate larger substituents in the bay area. 66 While for up to two small oxygen or fluorine substituents in 1,7-positions, presumably supported by hydrogen bonds donated by the opposing CH-acidic 6,12-hydrogens, planarization of the PBI scaffold is energetically achievable by packing effects in the solid state, 64 distortion is unavoidable for larger substituents such as chlorine 67 or bromine or an increasing number of substituents such as four phenoxy groups 68,69 (where the oxygens now not only sterically but also electrostatically repel each other).…”

Progress in the synthesis of perylene bisimide dyes

“…The first approach involves a halogen-exchange reaction of dibromo-PBA and subsequent imidization, whereas in the second the order of events is reversed, that is, the initial imidization of dibromo-PBA is followed by the Halex reaction of PBIs (Scheme 11). 70,72 The latter method is superior, as it eliminates the risk of the undesired replacement of fluoride atoms with amine during the imidization reaction, which was observed for the first method. Tetrafluoro-PBIs are synthesized from the respective tetrachloro-PBIs (Scheme 11).…”

“…The protocol employing KF and 18-crown-ether furnished difluoro-PBIs 39a-g from the respective dibromo-precursors 4a,d and 4e-i in modest yields (5-63%). 70,72,73 However, cyclohexyl derivative 39a was obtained in significantly better yield, when CNC + Cl − was used as a catalyst. 70 Fourfold substitution of chloride atoms with fluoride in the presence of CNC + Cl − proved even more challenging.…”