Abstract
AbstractA new perylene bisimide (PBI), with a fluorescence quantum yield up to unity, self‐assembles into two polymorphic supramolecular polymers. This PBI bears four solubilizing acyloxy substituents at the bay positions and is unsubstituted at the imide position, thereby allowing hydrogen‐bond‐directed self‐assembly in nonpolar solvents. The formation of the polymorphs is controlled by the cooling rate of hot monomer solutions. They show distinctive absorption profiles and morphologies and can be isolated in different polymorphic liquid‐crystalline states. The interchromophoric arrangement causing the spectral features was elucidated, revealing the formation of columnar and lamellar phases, which are formed by either homo‐ or heterochiral self‐assembly, respectively, of the atropoenantiomeric PBIs. Kinetic studies reveal a narcissistic self‐sorting process upon fast cooling, and that the transformation into the heterochiral (racemic) sheetlike self‐assemblies proceeds by dissociation via the monomeric state.
Highlights
Perylene bisimides (PBIs) are amongst the most studied colorants in supramolecular chemistry because of their unmatched combination of favorable optical and redox properties.[1,2,3,4] they can afford fluorescence quantum yields close to unity[5] and can be reduced at moderate potentials to give radical anions of high stability.[6]
This self-assembly was demonstrated for a variety of PBIs which form helices in the self-assembled state in solution[8,29,30] or the columnar liquid-crystalline phase.[31,32,33]
The new PBI1 was synthesized in a two-step procedure starting from N,N’-bis(1-phenylethyl)-1,6,7,12-tetramethoxyperylene-3,4:9,10-tetracarboxylic acid bisimide (1) which was obtained according to a recently reported method towards tetramethoxylated PBIs (Scheme 1).[46]
Summary
Perylene bisimides (PBIs) are amongst the most studied colorants in supramolecular chemistry because of their unmatched combination of favorable optical and redox properties.[1,2,3,4] they can afford fluorescence quantum yields close to unity[5] and can be reduced at moderate potentials to give radical anions of high stability.[6]. The substitution at bay positions further causes a distortion of the p system because of the repulsive interactions of substituents in close proximity, resulting in a conformational chirality of these dyes.[25] Usually, the interconversion process between the P- and M-atropoenantiomers in solution is fast and separation of the two is only possible by using sufficiently large, for example, bromo substituents,[26] by fixation of the chirality with tethers connecting the 1,7- and/or 6,12-positions,[27,28] or by introduction of 2,2’-biphenol units in 1,12- or 6,7-positions.[29] in most cases an equilibrium between the two atropoenantiomers exists, and strongly influences the self-assembly pathway by either homo- or heterochiral contacts of the chromophores.[29] Homochiral self-assembly leads to the formation of one-dimensional, helical fibers of either P- or M-chirality This self-assembly was demonstrated for a variety of PBIs which form helices in the self-assembled state in solution[8,29,30] or the columnar liquid-crystalline phase.[31,32,33] In contrast, heterochiral selfassembly yields two-dimensional structures of alternating Pand M-atropoenantiomers, only observed in singlecrystals of tetra- and octachloro-substituted PBIs.[34,35]. The fluorescence lifetime was determined to 4.8 ns which is in
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