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Herein, we report the synthesis and properties of a [6,6] hollow bilayer cylindrical nanoring (HBCNR) from a planar macrocycle via a Diels-Alder and Yamamoto coupling reaction. The fluorescence quantum yield of HBCNR was determined to be ΦF = 52%, which is four times higher than its precursor. In addition, its hollow nanoring configuration was also simulated by theoretical studies, and the tension energy was estimated to be 47.1 kcal/mol.

Herein, we report the synthesis, characterization, and photophysical properties of the crown-like structure of [3]cyclo-1,8-pyrenes (compounds 9 and 10). Planar pyrenyl arylene-ethynylene macrocycles are used as the precursors to synthesize these pyrene-based cycloarenes by [4 + 2] cycloaddition reaction with good yields. These molecules are confirmed by nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. The structure of 9 was unambiguously determined by single-crystal X-ray diffraction. Their photophysical properties are investigated by steady-state absorption, fluorescence, and time-resolved fluorescence spectroscopies, combined with theoretical calculations.

Herein, we design and synthesize a novel all-carbon supramolecular polymer host (SPh) containing conjugated macrocycles interconnected by a linear poly(para-phenylene) backbone. Applying the supramolecular host and fullerene C60 as the guest, we successfully construct a supramolecular polymeric heterojunction (SPh⊃C60). This carbon structure offers a means to explore the convex–concave π–π interactions between SPh and C60. The produced SPh was characterized by gel permeation chromatography, mass spectrometry, FTIR, Raman spectroscopy, and other spectroscopies. The polymeric segment can be directly viewed using a scanning tunneling microscope. Femtosecond transient absorption and fluorescence up-conversion measurements revealed femtosecond (≪300 fs) electron transfer from photoexcited SPh to C60, followed by nanosecond charge recombination to produce the C60 triplet excited state. The potential applications of SPh⊃C60 in electron- and hole-transport devices were also investigated, revealing that C60 incorporation enhances the charge transport properties of SPh. These results expand the scope of the synthesis and application of supramolecular polymeric heterojunctions., Herein, we design and synthesize a novel all-carbon supramolecular polymer host (SPh) containing conjugated macrocycles interconnected by a linear poly(para-phenylene) backbone.

Direct π-extension by the Scholl reaction for solution-based growth of armchair edges in curved macrocyclic hydrocarbon nanostructures is a great challenge. To date, several attempts at direct π-extension of small highly strained macrocycles have failed. Herein, we report a fixed two-bond approach for direct functionalization of small strained macrocyclic nanorings. The reaction occurs selectively to produce large π-extended molecular crowns with high yields. The design of these precursors features two peripheral C–C bonds that are readily incorporated into the extended aromatic moiety to overcome strain-induced side reactions, such as 1,2-phenyl shift. The crown-shaped macrocycle 10 showed a significant redshift (∼100 nm for absorption) compared with its precursor. This synthesis strategy could pave the way towards the π-extension of strained conjugated macrocycles and their potential applications in electron-transport devices.

The total synthesis of carbon onions is a significant challenge in the fields of materials science and organic chemistry. To date, the synthesis of even a fragment of fullerene C240 and its smallest carbon onion C60@C240 remains poorly explored. Herein, we demonstrate a bottom-up strategy to produce a novel π-extended molecular crown-shaped molecule (MC3) containing curved pentagonal and hexagonal units. This molecular crown represents a curved model compound for fullerene C240 and is fully characterized by NMR, mass spectrometry, UV-vis absorption, and from its emission spectra. Its supramolecular host–guest interaction with fullerene C60 is also investigated. MC3 and C60@MC3 can potentially be employed as seeds or templates for the bottom-up synthesis of fullerene C240 and the carbon onion C60@C240, respectively.

ConspectusDesigning and synthesizing topologically unique molecules is a long-term challenge for synthetic chemists. Classical polycyclic aromatic hydrocarbons (PAHs) are a large group of π-conjugated planar organic compounds with rich photophysical and electronic properties, while nonplanar/curved PAHs have different molecular orbital arrangements and demonstrate unique properties. The chemistry of curved aromatic molecules has been of significant interest to explore the relationship between π conjugation and molecular geometry, which offers an attractive combination of fundamental problems, potential applications, and aesthetic appeal. Remarkable advances have been made in the last few decades during the discovery of novel curved aromatic molecules, including corannulenes, fullerenes, and carbon nanotubes (CNTs). Especially, there has been increasing interest in making single-chirality CNTs and their curved molecular components (known as finite segments of CNTs) with a fixed geometry. The most representative examples of such organic molecules are cycloparaphenylenes (CPPs) and related carbon nanorings, which possess cylindrical topologies and nanoscale conjugated segments similar to CNTs. CPPs, as the shortest cross-section and the simplest structure of armchair CNTs, have been synthetically accessible since 2008. Recent years have witnessed breakthroughs and rapid development in the synthesis of CPP-based nanorings as well as their derived molecules. In these molecules, the distortion from aromatic planarity can induce radially oriented π systems and further affect their electronic, optical, self-assembly, and charge-transport characteristics. These unique and interesting carbon nanorings are potentially useful in a variety of optoelectronic and biomedical materials. It is well-known that extension of the π-conjugated system facilitates the delocalization of π electrons and the redistribution of electronic clouds, leading to rich diversification of physical properties in the fields of electronics, optics, and supramolecular chemistry. Therefore, the precise design and controllable synthesis of carbon nanorings with large π conjugation will promote important advances in synthetic chemistry. To date, a number of π-extended carbon nanorings have been reported, and they exhibit novel physicochemical properties resulting from their fascinating topologies and structures. However, challenges still remain in the synthesis of π-extended carbon nanorings and their structural analogues and exploration of their unique properties.In this Account, we give a brief overview of our efforts to synthesize large π-extended carbon nanorings using different strategies and explore their novel applications. In 2013 we started our research on the synthesis of carbon nanorings with large π-conjugated structures. This research project has led to (i) the successful preparation of a series of carbon nanorings with inserted PAHs, especially with various nanographenes inserted, such as hexa-peri-hexabenzocoronene; (ii) the design and synthesis of a series of carbon nanorings consisting solely of PAHs; and (iii) the initial synthesis of π-extended carbon-nanoring-based polymers as the long polymeric segments of CNTs, in which macrocyclic CPPs as the basic repeating blocks were covalently coupled together. Herein we describe in detail how these challenging π-extended carbon nanorings were synthesized, and their interesting physical properties are discussed.

Herein, we report the synthesis of a novel porous polymer, PS2, containing radially π-conjugated carbocycles and a linear phenylene backbone. The PS2-based membrane has a distinct small size cutoff (ca. 2.6 nm) and a major size at ∼1.5 nm for the size-selective separation of nanoparticles.

Conjugated polymers have attracted much attention for many years and have applications in various organic devices. Carbon nanotubes can be considered as all-carbon tube-shaped conjugated polymers c...

The physical properties of conjugated cycloparaphenylene-based materials highly depend on their sizes, geometries, and functional groups. Herein we reported a facile strategy to synthesize novel multifunctionalized octamethoxy-[8]cycloparaphenylene (OMe-[8]CPP). Remarkably, an unusual hypsochromic shift in the emission spectrum was observed compared to its unfunctionalized nanoring. In addition, the photoinduced electron transfer process between OMe-[8]CPP and a naphthalene diimide electron acceptor is studied for the first time. OMe-[8]CPP will provide a suitable platform for subsequent synthesis manipulations to construct interesting and unprecedented functional nanocarbon structures.

Herein, we explore phenanthrene as the building block to synthesize a hoop-shaped [6,6]carbon nanotube segment from a planar macocycle via a Diels-Alder reaction. The phenanthrene-based coronal nanohoop

Herein, we report a facile method of direct photodissociation of toluene molecules to photoluminescent carbon dots (CDs) under pulsed laser irradiation in the absence of surfactants or catalysts. The as-synthesized CDs with diameters 1.3–4.0 nm present regular emission peaks and the crystallographic structure of these species has been identified as graphite 2H from the analysis of high resolution transmission electron microscope (HRTEM) images, X-ray photoelectron spectroscopy (XPS) and Raman spectrum. In addition, First-Principle calculations were performed to discuss the photon-induced excitation in the photodissociation process. The results demonstrate that electrons can be transited from Highest Occupied Molecular Orbital (HOMO) to Lowest Unoccupied Molecular Orbital (LUMO) in toluene molecule by 248 nm single photon excitation process and the Stark effect plays a crucial role in the photodissociation process. These CDs exhibit excellent stable emission due to the stability of crystal structure, which could be considered for promising luminescent applications.

A green and efficient synthesis of aqueous CdTe quantum dots (QDs) embedded in inorganic salt enabled by co-precipitation is demonstrated, providing a new type of solid-state conversion material with emission colors covering green to red spectral regions. CdTe QDs were synthesized in the water phase, followed by incorporation into inorganic salt with the assistance of ethanol. Due to the protection of the tight matrix, the resulting composites exhibit good stability and processability as well as high photoluminescence properties. A white light emitting diode (WLED) applying the composites as a red color conversion layer with good luminescence properties is also fabricated, suggesting the promising application of the composites in solid-state lighting systems.

A novel type of aqueous fluorescent carbon dot (CD) was synthesized using citric acid as the only carbon source via an ammonium hydroxide modulated method, providing a blue color gamut. The amino group is considered to be the key factor in the high fluorescence of CDs and a model is established to investigate the mechanism of fluorescence. In addition, white light-emitting diodes (WLEDs) are fabricated by utilizing the prepared CDs and rare earth luminescent materials (SrSi2O2N2:Eu and Sr2Si5N8:Eu) as color conversion layers and UV-LED chips as the excitation light source. The WLEDs produce bright white light with attractive color rendering properties including a color rendering index of up to 95.1, a CIE coordinate of (0.33, 0.37), and a T c of 5447 K under a 100 mA driven current, indicating that the CDs are promising in the field of optoelectronic devices.