Synthesis and Optoelectronic Properties of Perylene Diimide-Based Liquid Crystals

Perylene diimide (PDI), initially synthesized and explored as an organic dye, has since gained significant recognition for its outstanding optical and electronic properties. Early research primarily focused on its vibrant coloration; however, the resolution of solubility challenges has revealed its broader potential. PDIs exhibit exceptional optical characteristics, including strong absorption and high fluorescence quantum yield, along with remarkable electronic properties, such as high electron affinity and superior charge carrier mobility. Furthermore, the robust π-π stacking interactions and liquid crystalline behavior of PDIs facilitate precise their self-assembly into highly ordered structures, positioning them as valuable materials for advanced applications in optoelectronics, photonics, and nanotechnology. This article provides a comprehensive review of the progress made in the design, synthesis, and optoelectronic performance of PDI-based liquid crystals. It explores how various substituents and their placement on the PDI core impact the properties of these liquid crystal molecules and discusses the challenges and opportunities that shape this rapidly evolving class of optical materials. This review is strictly focused on PDIs and does not cover their elongated or laterally extended derivatives, nor does it include monoimide or ester compounds.

Chiral diphenylacrylonitrile–perylene liquid crystal with circularly polarized luminescence in the aggregated state

Novel chiral diphenylacrylonitrile–perylene liquid crystal with excellent CPL propertyin aggregated state was reported.

Fluorescein-bridged Perylene Bisimide Dimer for Use as Liquid Crystal: Studies on Mesomorphic and Fluorescence Properties

A novel fluorescein-bridged perylene bisimide (PBI) dimer for liquid crystal (LC) with geometrically symmetric structure was developed. The mesomorphic results indicated that the energetically stable and unstable conformers of fluorescein fragments could lead to the transformation of mesophases from a hexagonal columnar mesophase to an uncertain phase at 136.9 °C in heating, whilst a stable hexagonal columnar mesophase maintained between 175.6 °C and 58.6 °C in cooling. The selectively excited fluorescence characters in THF solution demonstrated that the fluorescence resonance energy transfer (FRET) effect between fluorescein fragments and PBI unites could provide a means to effectively impose strong fluorescence of the dimeric PBIs modified with suitable chromophore at the N-imide position, which alternatively serves as a platform for the further study of multi-functional PBI-based LCs.

Columnar Mesomorphism of Board-Shaped Perylene, Diketopyrrolopyrrole, Isoindigo, Indigo, and Quinoxalino-Phenanthrophenazine Dyes

The properties of organic dyes depend as much on their intermolecular interactions as on their molecular structure. While it is generally predictable what supramolecular structure would be ideal for a specific application, the generation of specific supramolecular structures by molecular design and suitable processing methods remains to be a challenge. A versatile approach to different supramolecular structures has been the application of mesomorphism in conjunction with alignment techniques and self-assembly at interfaces. Reviewed here is the columnar mesomorphism of board-shaped dyes perylene, indigo, isoindigo, diketopyrrolopyrrole, and quinoxalinophenanthrophenazine. They generate a larger number of different supramolecular structures than conventional disc-shaped (discotic) mesogens because of their non-circular shape and directional intermolecular interactions. The mesomorphism of all but the perylene derivatives is systematically and comprehensively covered for the first time.

Synthesis and Properties of Maleic Acid Cholesteryl Monoester–Citric Acid Triester

A new maleic acid cholesteryl monoester–citric acid trimester (MACM-CAT) containing three cholesterol units has been synthesised successfully. The structure was characterised by a series of spectroscopic methods and thermal analysis including polarising optical microscopy. The results showed that MACM-CAT displayed a triangular-like ordered layered structure and exhibited a good liquid crystalline behaviour. The introduction of sodium citrate onto cholesterol units is favourable for the formation of hydrogen bonds of MACM-CAT and improvement of the stability. More importantly, the study provides a novel route for the synthesis of liquid crystalline materials.

Perylene-Based Liquid Crystals as Materials for Organic Electronics Applications

Columnar phases formed by the stacking of disclike molecules with an intimate π-π overlap forms a 1D pathway for the anisotropic charge migration along the columns. Columnar phases have great potential in organic electronic devices to be utilized as active semiconducting layers in comparison to organic single crystals or amorphous polymers in terms of processability, ease of handling, and high charge carrier mobility. Intelligent molecular engineering of perylene and its derivatives provided access to tune the physical properties and self-assembly behavior. The columnar phase formed by perylene derivatives has great potential in the fabrication of organic electronic devices. There are several positions on the perylene molecule, which can be functionalized to tune its self-assembly, as well as optoelectronic properties. Thus, many liquid-crystalline molecules stabilizing the columnar phase, which are based on perylene tetraesters, perylene diester imides, and perylene bisimides, have been synthesized over the years. Their longitudinal and laterally extended derivatives, bay-substituted derivatives exhibiting a columnar phase, are reported. In addition, several liquid-crystalline oligomers and polymers based on perylene derivatives were also reported. All such modifications provide an option to tune the energy levels of frontier molecular orbitals with respect to the work function of the electrodes in devices and also the processability of such materials. In this feature article, we attempt to provide an overview of the molecular design developed to tune the applicable properties and self-assembly of perylene derivatives as well as recent developments related to their application in the fabrication of organic solar cells, organic light-emitting diodes, and organic field-effect transistors.

Cholesterol-Based Compounds: Recent Advances in Synthesis and Applications

This review reports on the latest developments (since 2014) in the chemistry of cholesterol and its applications in different research fields. These applications range from drug delivery or bioimaging applications to cholesterol-based liquid crystals and gelators. A brief overview of the most recent synthetic procedures to obtain new cholesterol derivatives is also provided, as well as the latest anticancer, antimicrobial, and antioxidant new cholesterol-based derivatives. This review discusses not only the synthetic details of the preparation of new cholesterol derivatives or conjugates, but also gives a short summary concerning the specific application of such compounds.

Perylene bisimide with diphenylacrylonitrile on side-chain: strongly fluorescent liquid crystal with large pseudo Stokes shift based on AIE and FRET effect

A novel perylene bisimide (PBI) derivative with an AIE-active diphenylacrylonitrile unit positioned at the terminal N-imide position through a flexible spacer has been synthesized and characterized. The DSC, POM and XRD studies confirmed that it could self-assemble into a stable hexagonal columnar liquid-crystalline phase between 56 °C and 160 °C. This PBI derivative also exhibited strong fluorescence in solution, thin film and mesophase based on the cooperative mechanism of AIE and FRET between the diphenylacrylonitrile group and perylene moiety. The pseudo Stokes shift was as large as 283 nm, and the fluorescence quantum yields were as high as 0.62-0.79 in solution and 0.68-0.86 in solid state. This study provides a good strategy for converting the columnar liquid crystal with ACQ effect to one with the AIE effect, successfully filling the gap between the excellent columnar mesomorphic properties and strong fluorescence in solid state.

Perylene liquid crystals with multiple alkyl chains: investigation of the influence of peripheral alkyl chain number on mesomorphic and photophysical properties

Novel perylene liquid crystals with 2, 4 and 6 peripheral alkyl chains or 6, 8 and 10 peripheral alkyl chains at both the imide and bay-positions were investigated.

Novel AIE columnar liquid crystals: the influence of the number of diphenylacrylonitrile groups on the mesomorphic and fluorescence properties

Triphenylene derivatives with one or two diphenylacrylonitrile groups exhibited not only an ordered hexagonal columnar mesophase but also good AIE fluorescence properties in both solution and solid state.

Phenylacrylonitrile-bridging triphenylene dimers: the columnar liquid crystals with high fluorescence in both solid state and solution

The phenylacrylonitrile-bridging triphenylene dimers were prepared and exhibited the ordered hexagonal columnar mesophase and high fluorescence in both the solid state and solution.

Near-infrared fluorescent and columnar liquid crystal: synthesis, and photophysical and mesomorphic properties of triphenylene-Bodipy-triphenylene triad

The first near-infrared fluorescent and columnar liquid crystal based on Bodipy is achieved.