Effect of Core Twisting on Self‐Assembly and Optical Properties of Perylene Bisimide Dyes in Solution and Columnar Liquid Crystalline Phases

Abstract

A series of highly soluble and fluorescent core-twisted perylene bisimide dyes (PBIs) 3 a-f with different substituents at the bay area (1,6,7,12 positions of the perylene core) were synthesized and fully characterized by (1)H NMR, UV/Vis spectroscopy, MS spectrometry, and elemental analysis. The pi-pi aggregation properties of these new functional dyes were investigated in detail both in solution and in condensed phase by UV/Vis and fluorescence spectroscopy, vapor pressure osmometry (VPO), differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction. Concentration-dependent UV/Vis measurements and VPO analysis revealed that these core-twisted pi-conjugated systems show distinct self-dimerization equilibria in apolar solvent methylcyclohexane (MCH) with dimerization constants between 1.3x10(4) and 30 M(-1). The photoluminescence spectra of the dimers of PBIs 3 a-f exhibit bathochromic shifts of quite different magnitude which could be attributed to different longitudinal or rotational offsets between the dyes as well as differences in the respective pi-pi stacking distance. In condensed state, quite a few of these PBIs form luminescent rectangular or hexagonal columnar liquid crystalline phases with low isotropization temperatures. The effects of the distortion of the pi systems on their pi-pi stacking and the optical properties of the resultant stacks in solution and in LC phases have been explored in detail. In one case (3 a) a particularly interesting phase change from crystalline into liquid crystalline could be observed upon annealing that was accompanied by a transformation from non-fluorescent H-type into strongly fluorescent J-type packing of the dyes.

Influence of Molecular Aggregation on Electron Transfer at the Perylene Diimide/Indium-Tin Oxide Interface

“…488 nm) vibronic bands within the S 0 -S 1 manifold. [44][45][46][47] A 0-0/0-1 band ratio close to 1.6 is considered to be monomeric. 45,48,49 Here a 0-0/0-1 band ratio of 1.6 was measured for all four PDI-PAs when dissolved in the solvents from which they were adsorbed to ITO ( Figure S3 in SI), indicating they are essentially fully monomeric prior to film formation.…”

Emission properties of cyclodextrin dimers linked with perylene diimide—effect of cyclodextrin tumbling

“…[1][2][3][4] Perylene diimides (PDIs) derivatives effectively form supramolecular assemblies through p-p stacking interaction. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] In particular, supramolecular assemblies based on calixarenePDI conjugates show efficient energy and electron transfer properties due to the well-defined rigid and electron-rich scaffolds of calixarenes. [22][23][24][25][26][27] We have prepared PDI derivatives with a high emission property in aqueous solutions.…”

Optically Active Lyotropic Chromonic Liquid Crystal Based on Green Perylene Bisimide

“…Würthner et al reported that the substitution with bulky groups such as pyrrolidine at the bay area results in the twisting of aromatic core which could hinder a π-π stacking. 18 It is interesting, however, to note that the PBI molecules synthesized in this work still assemble into stacks of columnar aggregates subsequently forming a nematic LC phase due to the hydrophobic nature of the aromatic central core and the hydrophilic periphery. Further characterization of their LC behavior and structural analyses including X-ray diffraction and phase diagram studies are now in progress.…”

“…For example, Stalke et al 17 reported a series of compounds with different substituents at bay region of perylene core. Würthner et al 18 also reported a series of thermotropic liquid crystals based on PBI dyes with various substituents at the bay area (1,6,7,12-positions of the perylene core). According to their reports, PBI derivatives with electron-donating substituents at the bay area exhibit a large bathochromic shift of the absorption maxima (λmax), reflecting pronounced electronic interactions between the perylene core and the electron-donating groups at the bay area.…”

“…Additionally, the band shapes of both compounds 6 and 7 were broader as compared to compound 4, 5 or unsubstituted PBI, which is probably attributed to the loss of planarity of perylene core due to the steric hindrance at the bay area. 18 To confirm whether the PBI 7 is optically active or not, circular dichroism spectra were measured for both compounds 6 and 7 as illustrated in Figure 2b. Compared to the racemic compound 6 showing only a broad band without any particular peak, the PBI 7 exhibited three apparent bands, two with negative Cotton effect at 341 and 665 nm, and one with positive Cotton effect at 433 nm, respectively.…”