Hydrogen-Bonding-Induced Conformational Change from J to H Aggregate in Novel Highly Fluorescent Liquid-Crystalline Perylenebisimides

Abstract

A series of highly fluorescent liquid-crystalline perylenebisimide molecules having amide or ester linkage and end-capped by phenyl, monododecyloxy phenyl, or tridodecyloxy phenyl units have been synthesized and fully characterized. The amide-functionalized series self-organized to form H type aggregates regardless of their end-capping in organic solvents like tetrahydrofuran (THF), toluene, and dichloromethane. On the other hand, only the monododecyloxy phenyl end-capped molecule in the ester series showed a tendency to self-organize with a typical J type aggregation in toluene. In both series, the highest aggregation tendency was shown by the one having monododecyloxy phenyl end-capping, with the transition temperature from aggregated to molecularly dissolved species occurring at 60 °C for the amide and 50 °C for the ester molecule. At higher concentrations in toluene, the fluorescence spectra of the monododecyloxy phenyl and tridodecyloxy phenyl terminal-substituted amide derivatives showed the formation of a new peak corresponding to excimer emission at 670 nm. Thin drop cast films of the perylenebisimide ester and amide series gave only excimer emission ∼670 nm upon excitation. Thermal analysis using differential scanning calorimetry (DSC), polarized light microscopy (PLM), and powder X-ray diffraction measurements were utilized to study the liquid-crystalline (LC) characteristics of the molecules. Scanning electron micrograph (SEM) of thin drop-cast samples that were annealed in toluene showed the formation of supramolecular rods several micrometers in length, especially for the amide derivatives. The ester derivative, on the other hand, showed a leaflike morphology thus differentiating it from the amide series, which have both hydrogen bonding and π-π interactions to support self-organization.

Two‐Step Solution‐Processed Two‐Component Bilayer Phthalocyaninato Copper‐Based Heterojunctions with Interesting Ambipolar Organic Transiting and Ethanol‐Sensing Properties

“…Furthermore, a more significant increase can be found for the ratio of the intensities of A 737 / A 620 (0.88) of the Q absorptions of 2 than that for 1 , A 735 / A 650 = 0.65 in the QLS films, suggesting the more effective face‐to‐face π–π overlapping within the columnar assembly in the J ‐type aggregates of 2 than that for 1 . [24a,b] The orientation angle of the phthalocyanine ring with respect to the substrate in the QLS films of 1 and 2 was found to amount to 34.6° and 50.5°, respectively, according to the polarized UV–vis measurements (Figure S6 and Table S3, Supporting Information),[24c] revealing the “edge‐on” conformation ( J ‐aggregation) of the phthalocyanine molecules in the QLS films of both 1 and 2 . [20b] In addition, the obvious larger orientation angle of the phthalocyanine ring with respect to the substrate for 2 suggests the more upright π–π stacking arrangement and more effective face‐to‐face π–π overlapping within the columnar assembly in the QLS film of 2 than that of 1 .…”

Perylene Bisimide Dye Assemblies as Archetype Functional Supramolecular Materials

“…212 The effect of long alkoxy terminal substituents on self-assembly was elucidated by varying the number of these substituents (R 1 ) at the phenyl ring in PBIs 3-3a−c containing no, one, and three dodecyl groups, respectively. 213 Combining the properties of PBI building block with pentadecyl phenol (PDP) or cardanol, an unsaturated analogue of PDP, generates PBI derivatives 3-4a and 3-5, which also exhibited highly fluorescent aggregates in solution with a quantum yield ∼0.5 in MCH. 214 Furthermore, the morphology of the supramolecular architectures was studied by different microscopic techniques, including SEM, TEM, and AFM.…”

A Stimuli‐Responsive, Photoluminescent, Anthracene‐Based Liquid Crystal: Emission Color Determined by Thermal and Mechanical Processes

“…Our aim has been the development of a new class of photofunctional liquid crystals that change the emission properties on order-order phase transitions through external stimuli. [14] Recently, intensive work has been focused on photoluminescent liquid crystals [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] as they may be used for materials such as polarizing electroluminescent materials and laser devices. However, a change of the photoluminescent color based on the dynamic change of the LC assembled structures has not been observed, except for a few examples.…”