Chiral nanographenes exhibiting circularly polarized luminescence

Chiral nanographenes constitute an unconventional material class that deviates from planar graphene cutouts. They have gained considerable attention for their ability to exhibit circularly polarized luminescence (CPL), which offers new opportunities in chiral optoelectronics. Their unique π-conjugated architectures, coupled with the ability to introduce chirality at the molecular level, have made them powerful contenders in developing next-generation optoelectronic devices. This review thoroughly explores recent advances in the synthesis, structural design, and CPL performance of chiral nanographenes. We delve into diverse strategies for inducing chirality, including covalent functionalization, helically twisted frameworks, and heteroatom doping, each of which unlocks distinct CPL behaviors. In addition, we discuss the mechanistic principles governing CPL and future directions in chiral nanographenes to achieve high dissymmetry factors (glum) and tunable emission properties. We also discuss the key challenges in this evolving field, including designing robust chiral frameworks, optimizing CPL efficiency, and scaling up real-world applications. Through this review, we aim to shed light on recent developments in the bottom-up synthesis of structurally precise chiral nanographenes and evaluate their impact on the growing domain of circularly polarized luminescent materials.

A Geometrically Flexible Three-Dimensional Nanocarbon

The development of architecturally unique molecular nanocarbons by bottom-up organic synthesis is essential for accessing functional organic materials awaiting technological developments in fields such as energy, electronics, and biomedicine. Herein, we describe the design and synthesis of a triptycene-based three-dimensional (3D) nanocarbon, GFN-1, with geometrical flexibility on account of its three peripheral π-panels being capable of interconverting between two curved conformations. An effective through-space electronic communication among the three π-panels of GFN-1 has been observed in its monocationic radical form, which exhibits an extensively delocalized spin density over the entire 3D π-system as revealed by electron paramagnetic resonance and UV-vis-NIR spectroscopies. The flexible 3D molecular architecture of GFN-1, along with its densely packed superstructures in the presence of fullerenes, is revealed by microcrystal electron diffraction and single-crystal X-ray diffraction, which establish the coexistence of both propeller and tweezer conformations in the solid state. GFN-1 exhibits strong binding affinities for fullerenes, leading to host-guest complexes that display rapid photoinduced electron transfer within a picosecond. The outcomes of this research could pave the way for the utilization of shape and electronically complementary nanocarbons in the construction of functional coassemblies.

Alkoxylated Fluoranthene-Fused [3.3.3]Propellanes: Facile Film Formation against High π-Core Content

Solid-state assembling modes are as crucial as the chemical structures of single molecules for real applications. In this work, solid-state structures and phase-transition temperatures are investigated for a series of fluoranthene-fused [3.3.3]propellanes consisting of a rigid three-dimensional (3D) π-core and varying lengths of alkoxy groups. Compounds in this series with n-butoxy or longer alkoxy groups take an amorphous state at room temperature. In these molecules, rotatable biaryl-type bonds are not incorporated and high D3h molecular symmetry is retained. Therefore, π-fused [3.3.3]propellanes present a unique platform for amorphous molecular materials with low ratios of flexible alkoxy atoms to rigid π-core ones.

Triptycene Derivatives: From Their Synthesis to Their Unique Properties

Since the first preparation of triptycene, great progress has been made with respect to its synthesis and the understanding of its properties. Interest in triptycene-based systems is intense; in recent years, advances in the synthetic methodology and properties of new triptycenes have been reported by researchers from various fields of science. Here, an account of these new developments is given and placed in reference to earlier pivotal works that underpin the field. First, we discuss new approaches to the synthesis of new triptycenes. Progress in the regioselective synthesis of sterically demanding systems is discussed. The application of triptycenes in catalysis is also presented. Next, progress in the understanding of the relations between triptycene structures and their properties is discussed. The unique properties of triptycenes in the liquid and solid states are elaborated. Unique interactions, which involve triptycene molecular scaffolds, are presented. Molecular interactions within a triptycene unit, as well as between triptycenes or triptycenes and other molecules, are also evaluated. In particular, the summary of the synthesis and useful features will be helpful to researchers who are using triptycenes as building blocks in the chemical and materials sciences.

Diels-Alder Cycloaddition with CO, CO2, SO2, or N2 Extrusion: A Powerful Tool for Material Chemistry

Phenyl, naphthyl, polyarylphenyl, coronene, and other aromatic and polyaromatic moieties primarily influence the final materials' properties. One of the synthetic tools used to implement (hetero)aromatic moieties into final structures is Diels-Alder cycloaddition (DAC), typically combined with Scholl dehydrocondensation. Substituted 2-pyranones, 1,1-dioxothiophenes, and, especially, 1,3-cyclopentadienones are valuable substrates for [4 + 2] cycloaddition, leading to multisubstituted derivatives of benzene, naphthalene, and other aromatics. Cycloadditions of dienes can be carried out with extrusion of carbon dioxide, carbon oxide, or sulphur dioxide. When pyranones, dioxothiophenes, or cyclopentadienones and DA cycloaddition are aided with acetylenes including masked ones, conjugated or isolated diynes, or polyynes and arynes, aromatic systems are obtained. This review covers the development and the current state of knowledge regarding thermal DA cycloaddition of dienes mentioned above and dienophiles leading to (hetero)aromatics via CO, CO2, or SO2 extrusion. Particular attention was paid to the role that introduced aromatic moieties play in designing molecular structures with expected properties. Undoubtedly, the DAC variants described in this review, combined with other modern synthetic tools, constitute a convenient and efficient way of obtaining functionalized nanomaterials, continually showing the potential to impact materials sciences and new technologies in the nearest future.

Removal of hazardous dyes, toxic metal ions and organic pollutants from wastewater by using porous hyper-cross-linked polymeric materials: A review of recent advances

Water quality plays a central role in the well-being of all the living organisms on planet Earth. The ever-increasing human population and consequently increasing industrialization, urbanization, and chemically boosted cultivation are rapidly contaminating already stressed water resources. The availability of clean drinking water has become scarce for masses across the globe, and this situation is becoming alarming in developing countries. Therefore, the immediate need for cost-effective, easily accessible, eco-friendly, portable, thermally efficient, and chemically stable technologies and materials is desperately felt to meet the high global demand for clean water. To search for effective materials for wastewater treatment, the hyper-cross-linked porous polymers (HCPs) have emerged as an excellent class of porous materials for wastewater treatment due to their unique features of high surface area, tunability, biodegradability, and chemical versatility. This review describes the advances in fabrication strategies and the efficient utilization of hyper-cross-linked porous polymers for wastewater treatment. Moreover, this review specifically discusses the hyper-cross-linked porous polymers effectiveness for the separation of the dyes, nutrients, inorganic ions, organic contaminants, and toxic metals ions. Finally, the review provides insight into the challenges and prospects in the area of hyper-cross-linked porous polymers. Overall, the hyper-cross-linked porous polymers with empowering proper functionalization can provide an opportunity for the wastewater treatment not only to remove toxic contaminants but also to make contaminated water useful for various applications.

Chiral Triptycenes: Concepts, Progress and Prospects

Triptycenes have been established as unique scaffolds because of their backbone π-structure with a propeller-like shape and saddle-like cavities. They are some of the key organic molecules that have been extensively studied in polymer chemistry, in supramolecular chemistry and in material science. Triptycenes become chiral molecules when substituents are unsymmetrically attached in at least two of their different aromatic rings. This Minireview highlights the chirality of triptycenes from basics to an advanced stage for the development of functional molecules.

Chiral Triptycenes in Supramolecular and Materials Chemistry

Triptycenes are an intriguing class of organic molecules with several unusual characteristics, such as a propeller-like shape, saddle-like cavities around a symmetrical scaffold, a rigid π-framework. They have been extensively studied and proposed as key synthons for a variety of applications in supramolecular chemistry and materials science. When decorated with an appropriate substitution pattern, triptycenes can be chiral, and, similarly to other popular chiral π-extended synthons, can express chirality robustly, efficiently, and with relevance to chiroptical spectroscopies. This minireview highlights and encompasses recent advances in the synthesis of chiral triptycenes and in their introduction as molecular scaffolds for the assembly of functional supramolecular materials.

Helical Assemblies of One-Dimensional Supramolecular Polymers Composed of Helical Macromolecules: Generation of Circularly Polarized Light Using an Infinitesimal Chiral Source

We report the synthesis of one-dimensional supramolecular polymers composed of one-handed helical macromolecules bearing fluorescent pendant groups and the generation of circularly polarized light on the basis of hierarchical chiral amplification starting from a tiny amount of chiral substituent. Copolymerization of benzo[1,2-b:4,5-b']dithiophene-appended achiral/chiral isocyanides (99:1, mol/mol) with a solid-state photoluminescence feature afforded submicrometer supramolecular fibers, in which almost perfect single-handed helical polyisocyanides were noncovalently connected end to end. The resulting helical supramolecular polymers were further helically assembled to form a cholesteric liquid crystal film with an intense circularly polarized luminescence (CPL) signal. Surprisingly, the supramolecular system containing only 0.01 mol % of the chiral monomer unit also emitted the observable circularly polarized light owing to multiple chiral amplification from an infinitesimal point chirality to helical chirality and then to supramolecular chirality. Furthermore, chiral information was efficiently transferred from the helically assembled supramolecular system containing 1 mol % of the chiral unit to achiral dye molecules blended in the film, allowing full-color tunable induced CPL with luminescence dissymmetry factors greater than 1.0 × 10^-2. This unprecedentedly strong chiral amplification enables the creation of helical supramolecular polymers and chirally assembled systems with various chiral functions based solely on an infinitesimal chiral source.