Synthesis of Oligoparaphenylene-Derived Nanohoops Employing an Anthracene Photodimerization–Cycloreversion Strategy

Synthesis and Properties of a Strained Triple Nanohoop

A strained triple nanohoop with a shared central benzene unit is synthesized using a threefold intramolecular ring-closing approach. Among the five possible constitutional isomers, the isomer with the highest D3h symmetry is isolated, the structure of which contains three nanohoop blades and a central hexaphenylbenzene unit. The structure is elucidated using NMR spectroscopy and mass spectrometry. The optical and electrochemical properties are investigated, revealing a moderate fluorescence quantum yield of 40 %. A water-soluble nanomaterial is prepared using a nanoparticle encapsulation method, and a fluorescence quantum yield of 10 % is retained, which demonstrates the potential of the nanomaterial in biological systems.

π-Conjugated Nanohoops: A New Generation of Curved Materials for Organic Electronics

Nanohoops, cyclic association of π-conjugated systems to form a hoop-shaped molecule, have been widely developed in the last 15 years. Beyond the synthetic challenge, the strong interest towards these molecules arises from their radially oriented π-orbitals, which provide singular properties to these fascinating structures. Thanks to their particular cylindrical arrangement, this new generation of curved molecules have been already used in many applications such as host-guest complexation, biosensing, bioimaging, solid-state emission and catalysis. However, their potential in organic electronics has only started to be explored. From the first incorporation as an emitter in a fluorescent organic light emitting diode (OLED), to the recent first incorporation as a host in phosphorescent OLEDs or as charge transporter in organic field-effect transistors and in organic photovoltaics, this field has shown important breakthroughs in recent years. These findings have revealed that curved materials can play a key role in the future and can even be more efficient than their linear counterparts. This can have important repercussions for the future of electronics. Time has now come to overview the different nanohoops used to date in electronic devices in order to stimulate the future molecular designs of functional materials based on these macrocycles.

Host-Guest Chemistry in Binary and Ternary Complexes Utilizing π-Conjugated Carbon Nanorings

The carbon nanorings, possessing a radial π system, have garnered significant attention primarily due to their size-dependent photophysical properties and the presence of a unique curved π-conjugated cavity. This is evidenced by the rapid proliferation of publications. Furthermore, the integration of building blocks into CPP skeletons can confer [n]CPPs with novel and exceptional photophysical and electronic characteristics, as well as chiral properties and host-guest interactions, thereby augmenting the diversity of [n]CPPs. Notably, the curved π surface structures and concave cavity of carbon nanorings enable them to host aromatic or non-aromatic guests with a complementarily curved surface, resulting in interesting binary or ternary complexes. This review provides a comprehensive treatment of literature reports on binary and ternary complexes, focusing on both their host-guest interactions and properties. It is important to note that the scope of this review is limited to host-guest chemistry in binary and ternary complexes based on π-conjugated carbon nanorings.

Facile synthesis and characterization of aza-bridged all-benzenoid quinoidal figure-eight and cage molecules

Synthesis of conjugated compounds with unusual shape-persistent structures remains a challenge. Herein, utilizing thermodynamically reversible intermolecular Friedel-Crafts alkylation, a dynamic covalent chemistry (DCC) reaction, we facilely synthesized a figure-eight shaped macrocycle FEM and cage molecules CATPA/CACz. X-ray crystallographic analysis confirmed the chemical geometries of tetracation FEM4+(PF6 -)4 and hexacation CACz6+(SbF6 -)6. FEM and CATPA displayed higher photoluminescence quantum yield in solid states compared to that in solution, whereas CACz gave the reverse result. DFT calculations showed that fluorescence-related frontier molecular orbital profiles are mainly localized on their arms consisting of a p-quinodimethane (p-QDM) unit and two benzene rings of triphenylamine or carbazole. Owing to their space-confined structures, variable-temperature 1H NMR measurements showed that FEM, CATPA and FEM4+ have intramolecular restricted motion of phenyl rings on their chromophore arms. Accordingly, FEM and CATPA with flexible triphenylamine subunits displayed aggregation-induced emission behavior (AIE), whereas CACz with a rigid carbazole subunits structure showed no AIE behavior.

Synthesis of π-Conjugated Chiral Aza/Boracyclophanes with a meta and para Substitution

We herein describe the synthesis of a new class of axially chiral aza/boracyclophanes (BDN1, BXN1, BDB1 and BXB1) using binaphthyls as chiral building blocks and the main-group (B/N) chemistry with tunable electronic effects. All macrocycles substituted with triarylamine donors or triarylborane acceptors are strongly luminescent. These macrocycles showed two distinct meta and para π-conjugation pathways, leading to the formation of quasi figure-of-eight and square-shaped conformations. Interestingly, comparison of such structural models revealed that the former type of macrocycles BXN1 and BXB1 gave higher racemization barriers relative to the other ones. The results reported here may provide a new approach to engineer the optical stability of π-conjugated chiral macrocycles by controlling π-substitution patterns. The ring constraints induced by macrocyclization were also demonstrated to contribute to the configurational persistence as compared with the open-chain analogues p-BTT and m-BTT.

The Key Role of Molecular Packing in Luminescence Property: From Adjacent Molecules to Molecular Aggregates

The luminescence materials act as the key components in many functional devices, as well as the detection and imaging systems, which can be permeated in each aspect of modern life, and attract more and more attention for the creative technology and applications. In addition to the diverse properties of organic luminogens, the multiple molecular packing at aggregated states frequently offers new and/or exciting performance. However, there still lacks comprehensive analysis of molecular packing in these organic materials, resulting in an increased gap between molecular design and practical applications. In this review, from the basic knowledge of organic compounds as single molecules, to the discernable property of excimer, charge transfer (CT) complex or self-assembly systems by adjacent molecules, and finally to the opto-electronic performance of molecular aggregates, the relevant factors to molecular packing and practical applications are discussed.

Synthesis of a water-soluble naphthalene-based macrocycle and its host-guest properties

Reported here is the synthesis of a naphthalene-based macrocycle bearing anionic carboxylato groups on the rims along with its complexation with cationic guests in aqueous media. The macrocycle could strongly bind guests in a molecular clip model with association constants of 106-107 M-1.

Bismacrocycle: Structures and Applications

In the past half-century, macrocycles with different structures and functions, have played a critical role in supramolecular chemistry. Two macrocyclic moieties can be linked to form bismacrocycle molecules. Compared with monomacrocycle, the unique structures of bismacrocycles led to their specific recognition and assembly properties, also a wide range of applications, including molecular recognition, supramolecular self-assembly, advanced optical material construction, etc. In this review, we focus on the structure of bismacrocycle and their applications. Our goal is to summarize and outline the possible future development directions of bismacrocycle research.

Theoretical Study on a Supramolecular Dimeric Structure Constructed by Metallofullerene Y3N@C80 and Figure-of-Eight Nanoring

A new supramolecular complex with a dimeric structure (2Y₃N@C₈₀⊂OPP) constructed by metallofullerene Y₃N@I_h-C₈₀ and figure-of-eight molecular nanoring of oligoparaphenylene (OPP) was investigated using dispersion-corrected density functional theory (DFT-D3). The interactions between the Y₃N@I_h-C₈₀ guest and the OPP host were studied theoretically at the B3LYP-D3/6-31G(d)∼SDD level. By analyzing geometric characteristics and host-guest binding energies, it is revealed that the OPP is an ideal host molecule for the Y₃N@I_h-C₈₀ guest. Typically, the OPP can well induce the orientation of the endohedral Y₃N cluster on the plane of nanoring. Meanwhile, the configuration of the dimeric structure demonstrates that OPP presents excellent elastic adaptability and shape flexibility during the encapsulation of Y₃N@I_h-C₈₀. Highly accurate binding energy suggests that 2Y₃N@C₈₀⊂OPP (∼-443.82 kJ mol^-1 at the ωB97M-V/def2-QZVPP level of theory) is an extremely stable host-guest complex. Thermodynamic information indicates that the formation of the 2Y₃N@C₈₀⊂OPP dimer is thermodynamically spontaneous. Furthermore, electronic property analysis reveals that this dimeric structure has a strong electron-attracting ability. Energy decomposition and real-space function analyses of host-guest interactions reveal the characteristics and nature of the noncovalent interactions in the supramolecules. These results provide theoretical support for the design of new host-guest systems based on metallofullerene and nanoring.

Stable Crystalline Nanohoop Radical and Its Self-Association Promoted by van der Waals Interactions

A stable nanohoop radical (OR3) combining the structures of cycloparaphenylene and an olympicenyl radical is synthesized and isolated in the crystalline state. X-ray crystallographic analysis reveals that OR3 forms a unique head-to-tail dimer that further aggregates into a one-dimensional chain in the solid state. Variable-temperature NMR and concentration-dependent absorption measurements indicate that the π-dimer is not formed in solution. An energy decomposition analysis indicates that van der Waals interactions are the driving force for the self-association process, in contrast with other olympicenyl derivatives that favor π-dimerization. The physical properties in solution phase have been studied, and the stable cationic species obtained by one-electron chemical oxidation. This study offers a new molecular design to modulate the self-association of organic radicals for overcoming the spin-Peierls transition, and to prepare novel nanohoop compounds with spin-related properties.

Divergent Synthesis of Helical Ketone Enabled by Rearrangement of Spiro Carbocation

An acid-mediated electrophilic cyclization of 2-alkynyl-1,1'-biphenyls for the divergent synthesis of angular, bent, and zigzag fused nonplanar conjugated organic molecules was realized. The key feature of this reaction is a Wagner-Meerwein-type rearrangement via a spiro carbocation intermediate, which was formed by electrophilic cyclization of the 9H-fluoren-9-one derivative at the meta position. The products can be advanced to helical fluorenes, which exhibit high fluorescence quantum yields.

Supramolecular photosensitizers using extended macrocyclic hosts for photodynamic therapy with distinct cellular delivery

Two hydrophilic macrocycles can strongly bind hypocrellin B. The resulting supramolecular photosensitizers show excellent photodynamic efficiency with different cellular delivery.

An unexpected dual-emissive luminogen with tunable aggregation-induced emission and enhanced chiroptical property

In the literature, organic materials with both aggregation-induced emission (AIE) and aggregation-caused quenching (ACQ) effects that can emit with multiple bands both in the solution and aggregated state are rarely reported. Herein we report a novel chiral dual-emissive bismacrocycle with tunable aggregation-induced emission colors. A facile four-step synthesis strategy is developed to construct this rigid bismacrocycle, (1,4)[8]cycloparaphenylenophane (SCPP[8]), which possesses a 1,2,4,5-tetraphenylbenzene core locked by two intersecting polyphenylene-based macrocycles. The luminescent behavior of SCPP[8] shows the unique characteristics of both ACQ effect and AIE effect, inducing remarkable redshift emission with near white-light emission. SCPP[8] is configurationally stable and possesses a novel shape-persistent bismacrocycle scaffold with a high strain energy. In addition, SCPP[8] displays enhanced circularly polarized luminescence properties due to AIE effect.

Organic materials with both aggregation induced emission (AIE) and aggregation-caused quenching (ACQ) effects that can emit with multiple wavelengths in the solution and aggregated state are rarely reported. Here, the authors report a chiral dual-emissive bismacrocycle which shows the unique ACQ and AIE effects inducing redshift emission with near white-light emission.

Selective and Cooperative Photocycloadditions within Multistranded Aromatic Sheets

A series of aromatic helix-sheet-helix oligoamide foldamers composed of several different photosensitive diazaanthracene units have been designed and synthesized. Molecular objects up to 7 kDa were straightforwardly produced on a 100 mg scale. Nuclear magnetic resonance and crystallographic investigations revealed that helix-sheet-helix architectures can adopt one or two distinct conformations. Sequences composed of an even number of turn units were found to fold in a canonical symmetrical conformation with two helices of identical handedness stacked above and below the sheet segment. Sequences composed of an odd number of turns revealed a coexistence between a canonical fold with helices of opposite handedness and an alternate fold with a twist within the sheet and two helices of identical handedness. The proportions between these species could be manipulated, in some cases quantitatively, being dependent on solvent, temperature, and absolute control of helix handedness. Diazaanthracene units were shown to display distinct reactivity toward [4 + 4] photocycloadditions according to the substituent in position 9. Their organization within the sequences was programmed to allow photoreactions to take place in a specific order. Reaction pathways and kinetics were deciphered and product characterized, demonstrating the possibility to orchestrate successive photoreactions so as to avoid orphan units or to deliberately produce orphan units at precise locations. Strong cooperative effects were observed in which the photoreaction rate was influenced by the presence (or absence) of photoadducts in the structure. Multiple photoreactions within the aromatic sheet eventually lead to structure lengthening and stiffening, locking conformational equilibria. Photoproducts could be thermally reverted.

Supramolecular-controlled regioselective photochemical [4+4] cycloaddition within Cp*Rh-based metallarectangles

Photochemical reactions are vital synthetic means for the synthesis of natural products as well as highly strained molecules. However, it remains an inherent challenge to control the chemo- and regioselectivity...

Nanosized Carbon Macrocycles Based on a Planar Chiral Pseudo Meta- [2.2]Paracyclophane

Structural designs combining cycloparaphenylenes (CPPs) backbone with planar chiral [2.2]Paracyclophane ([2.2]PCP) lead to optical-active chiral macrocycles with intriguing properties. X-ray crystal analysis revealed aesthetic necklace-shaped structures and size-dependent packages with long-range channels. The macrocycles exhibit unique photophysical properties with high fluorescence quantum yield of up to 82%, and the fluorescent color varies with ring size. In addition, size-dependent chiroptical properties with moderately large CPL dissymmetry factor of 10 -3 and CPL brightness in the range of 30 - 40 M -1 cm -1 were observed.

A Conjugated Figure-of-Eight Oligoparaphenylene Nanohoop with Adaptive Cavities Derived from Cyclooctatetrathiophene Core

A fully conjugated figure-of-eight nanohoop is presented with facile synthesis. The molecule's lemniscular skeleton features the combination of two strained oligoparaphenylene loops and a flexible cyclooctatetrathiophene core. Its rigid yet guest-adaptive cavities enable the formation of the peanut-like 1:2 host-guest complexes with C₆₀ or C₇₀ , which have been confirmed by X-ray crystallography and characterized in solution. Further computational studies suggest notable geometric variations and non-covalent interactions of the cavities upon binding with different fullerenes, as well as overall conjugation comparable to cycloparaphenylenes.

Enantioselective Construction of Modular and Asymmetric Baskets

The precise positioning of functional groups about the inner space of abiotic hosts is a challenging task and of interest for developing more effective receptors and catalysts akin to those found in nature. To address it, we herein report a synthetic methodology for preparing basket-like cavitands comprised of three different aromatics as side arms with orthogonal esters at the rim for further functionalization. First, enantioenriched A (borochloronorbornene), B (iodobromonorbornene), and C (boronorbornene) building blocks were obtained by stereoselective syntheses. Second, consecutive A-to-B and then AB-to-C Suzuki-Miyaura (SM) couplings were optimized to give enantioenriched ABC cavitand as the principal product. The robust synthetic protocol allowed us to prepare (a) an enantioenriched basket with three benzene sides and each holding either tBu, Et, or Me esters, (b) both enantiomers of a so-called "spiral staircase" basket with benzene, naphthalene, and anthracene groups surrounding the inner space, and (c) a photo-responsive basket bearing one anthracene and two benzene arms.

Fullerene Wires Assembled Inside Carbon Nanohoops

Carbon-nanohoop structures featuring one or more round-shaped cavities represent ideal supramolecular hosts for spherical fullerenes, with potential to form host-guest complexes that perform as organic semiconductors in the solid state. Due to the tight complexation between the shape-complementary hosts and guests, carbon nanohoops have the potential to shield fullerenes from water and oxygen, known to perturb the electron-transport process. Many nanohoop receptors have been found to form host-guest complexes with fullerenes. However, there is only a little or no control over the long-range order of encapsulated fullerenes in the solid state. Consequently, the potential of these complexes to perform as organic semiconductors is rarely evaluated. Herein, we present a survey of all known nanohoop-fullerene complexes, for which the solid-state structures were obtained. We discuss and propose instances where the inclusion fullerene guests form discrete supramolecular wires, which might open up possibilities for their use in electronic devices.

Naphthodithiophene Diimide Based Chiral π-Conjugated Nanopillar Molecules

The synthesis, structures, and properties of [4]cyclonaphthodithiophene diimides ([4]C-NDTIs) are described. NDTIs as important n-type building blocks were catenated in the α-positions of thiophene rings via an unusual electrochemical-oxidation-promoted macrocyclization route. The thiophene-thiophene junction in [4]C-NDTIs results in an ideal pillar shape. This interesting topology, along with appealing electronic and optical properties inherited from the NDTI units, endows the [4]C-NDTIs with both near-infrared (NIR) light absorptions, strong excitonic coupling, and tight encapsulation of C₆₀ . Stable orientations of the NDTI units in the nanopillars lead to stable inherent chirality, which enables detailed circular dichroism studies on the impact of isomeric structures on π-conjugation. Remarkably, the [4]C-NDTIs maintain the strong π-π stacking abilities of NDTI units and thus adopt two-dimensional (2D) lattice arrays at the molecular level. These nanopillar molecules have great potential to mimic natural photosynthetic systems for the development of multifunctional organic materials.

Cycloparaphenylene Double Nanohoop: Structure, Lamellar Packing, and Encapsulation of C60 in the Solid State

A new member of the cycloparaphenylene double-nanohoop family was synthesized. Its π-framework features two oval cavities that display different shapes depending on the crystallization conditions. Incorporation of the peropyrene bridge within the nanoring cycles via bay-regions alleviates steric effects and thus allows 1:1 complexation with C₆₀ in the solid state. This nanocarbon adopts a lamellar packing motif, and our results suggest that the structural adjustment of this double nanohoop could enable its use in supramolecular and semiconductive materials.

Photooxidation-Driven Purely Organic Room-Temperature Phosphorescent Lysosome-Targeted Imaging

The construction of host-guest-binding-induced phosphorescent supramolecular assemblies has become one of increasingly significant topics in biomaterial research. Herein, we demonstrate that the cucurbit[8]uril host can induce the anthracene-conjugated bromophenylpyridinium guest to form a linear supramolecular assembly, thus facilitating the enhancement of red fluorescence emission by the host-stabilized charge-transfer interactions. When the anthryl group is photo-oxidized to anthraquinone, the obtained linear nanoconstructs can be readily converted into the homoternary inclusion complex, accompanied by the emergence of strong green phosphorescence in aqueous solution. More intriguingly, dual organelle-targeted imaging abilities have been also distinctively achieved in nuclei and lysosomes after undergoing photochemical reaction upon UV irradiation. This photooxidation-driven purely organic room-temperature phosphorescence provides a convenient and feasible strategy for supramolecular organelle identification to track specific biospecies and physiological events in the living cells.

Molecular Plumbing to Bend Self-Assembling Peptide Nanotubes

Light-induced molecular piping of cyclic peptide nanotubes to form bent tubular structures is described. The process is based on the [4+4] photocycloaddition of anthracene moieties, whose structural changes derived from the interdigitated flat disposition of precursors to the corresponding cycloadduct moieties, induced the geometrical modifications in nanotubes packing that provokes their curvature. For this purpose, we designed a new class of cyclic peptide nanotubes formed by β- and α-amino acids. The presence of the former predisposes the peptide to stack in a parallel fashion with the β-residues aligned along the nanotube and the homogeneous distribution of anthracene pendants.

Palladium-Catalyzed Desymmetric Intermolecular C-N Coupling Enabled by a Chiral Monophosphine Ligand Derived from Anthracene Photodimer

The development of chiral ligands with privileged scaffolds plays an important role in transition-metal-catalyzed asymmetric reactions. Herein we present anthracene-photodimer-derived chiral monophosphine ligand 1, which features dual chirality and a rigid scaffold. This ligand exhibits remarkable efficiency in Pd-catalyzed desymmetric intermolecular C-N coupling under mild conditions with excellent chemo- and enantioselectivity.

A Highly Strained All-Phenylene Conjoined Bismacrocycle

Herein, we report the precise synthesis of a 3D highly strained all-phenylene bismacrocycle, termed conjoined (1,4)[10]cycloparaphenylenophane (SCPP[10]). This structure consists of a twisted benzene ring which is bridged twice by phenylene units anchored in two para-positions. The conjoined structure of SCPP[10] was confirmed in real space at the atomic scale by scanning tunneling microscopy. Theoretical calculations indicate that this bismacrocycle has a very high strain energy of 110.59 kcal mol^-1 and the largest interphenylene torsion angle of 46.07° caused by multiple repulsive interactions. Furthermore, a 1:2 host-guest complex of SCPP[10] and [6,6]-phenyl-C₆₁ -butyric acid methyl ester was investigated, which represents the first peanut-shaped 1:2 host-guest complex based on bismacrocycles.

Conjugated Molecular Nanotubes

Molecular compounds with permanent tubular architectures displaying radial π-conjugation are exceedingly rare. Their radial and axial delocalization presents them with unique optical and electronic properties, such as remarkable tuning of their Stokes shifts, and redox switching between global and local aromaticity. Although these tubular compounds display large internal void spaces, these attributes have not been extensively explored, thus presenting future opportunities in the development of materials. By using cutting-edge synthetic methodologies to bend aromatic surfaces, large opportunities in synthesis, property discovery, and applications are expected in new members of this family of conjugated molecular nanotubes.

Cycloparaphenylene-Phenalenyl Radical and Its Dimeric Double Nanohoop*

The first example of a neutral spin-delocalized carbon-nanoring radical was achieved by integration of the open-shell phenalenyl unit into cycloparaphenylene (CPP). Spin distribution in this hydrocarbon is localized primarily on the phenalenyl segment and partially on the CPP segment as a consequence of steric and electronic effects. The resulting geometry is reminiscent of a diamond ring, with pseudo-perpendicular arrangement of the radial and the planar π-surface. The phenylene rings attached directly to the phenalenyl unit give rise to a steric effect that governs a highly selective dimerization pathway, yielding a giant double nanohoop. Its π-framework made of 158 sp2 -carbon atoms was elucidated by single-crystal X-ray diffraction, which revealed a three-segment CPP-peropyrene-CPP structure. This nanocarbon shows a fluorescence profile characteristic of peropyrene, regardless of which segment gets excited. These results in conjunction with DFT suggest that adjusting the size of the CPP segments in this double nanohoop could deliver donor-acceptor systems.

Conjugated Nanohoops Incorporating Donor, Acceptor, Hetero- or Polycyclic Aromatics

In the last 13 years several synthetic strategies were developed that provide access to [n]cycloparaphenylenes ([n]CPPs) and related conjugated nanohoops. A number of potential applications emerged, including optoelectronic devices, and their use as templates for carbon nanomaterials and in supramolecular chemistry. To tune the structural or optoelectronic properties of carbon nanohoops beyond the size‐dependent effect known for [n]CPPs, a variety of aromatic rings other than benzene were introduced. In this Review, we provide an overview of the syntheses, properties, and applications of conjugated nanohoops beyond [n]CPPs with intrinsic donor/acceptor structure or such that contain acceptor, donor, heteroaromatic or polycyclic aromatic units within the hoop as well as conjugated nanobelts.

Conformation-Changeable π-Electronic Systems with Metastable Bent-Core Conformations and Liquid-Crystalline-State Electric-Field-Responsive Properties

This study focused on the use of nonconventional bent-core π-electronic systems, 2,2'-bipyrroles substituted with modified benzoyl units, as building units of stimuli-responsive assemblies. Electric-field-responsive mesophase behaviors were observed in homochiral synclinic ferroelectric smectic C structures comprising the syn conformations. Electric-field application induced changes in the polarized optical microscopy textures with dynamic behaviors derived from the conversion from twisted to untwisted states.

Supramolecular-induced regiocontrol over the photochemical [4 + 4] cyclodimerization of NHC- or azole-substituted anthracenes

Thanks to the impressive control that microenvironments within enzymes can have over substrates, many biological reactions occur with high regio- and stereoselectivity. However, comparable regio- and stereoselectivity is extremely difficult to achieve for many types of reactions, particularly photochemical cycloaddition reactions in homogeneous solutions. Here, we describe a supramolecular templating strategy that enables photochemical [4 + 4] cycloaddition of 2,6-difunctionalized anthracenes with unique regio- and stereoselectivity and reactivity using a concept known as the supramolecular approach. The reaction of 2,6-azolium substituted anthracenes H₄-L(PF₆)₂ (L = 1a–1c) with Ag₂O yielded complexes anti-[Ag₂L₂](PF₆)₄ featuring an antiparallel orientation of the anthracene groups. Irradiation of complexes anti-[Ag₂L₂](PF₆)₄ proceeded under [4 + 4] cycloaddition linking the two anthracene moieties to give cyclodimers anti-[Ag₂(2)](PF₆)₂. Reaction of 2,6-azole substituted anthracenes with a dinuclear complex [Cl-Au-NHC–NHC-Au-Cl] yields tetranuclear assemblies with the anthracene moieties oriented in syn-fashion. Irradiation and demetallation gives a [4 + 4] syn-photodimer of two anthracenes. The stereoselectivity of the [4 + 4] cycloaddition between two anthracene moieties is determined by their orientation in the metallosupramolecular assemblies.

A supramolecular templating strategy that enables the photochemical [4 + 4] cycloaddition of 2,6-difunctionalized anthracene derivatives with unique stereoselectivity has been developed based on metal-NHC units.

Synthesis of Enantiopure C2-Symmetric Anthracenophane and Dimerization En Route to Multiple-Bridged Cyclophanes

We report the stereocontrolled synthesis of enantiopure C₂-symmetric anthracenophanes and their derivatization to D₂-symmetric multiple-bridged cyclophanes via photoinduced [4 + 4] dimerization.

Synthesis of Giant π-Extended Molecular Macrocyclic Rings as Finite Models of Carbon Nanotubes Displaying Enriched Size-Dependent Physical Properties

Bottom-up synthesis of π-extended macrocyclic carbon rings is promising for constructing length- and diameter-specific carbon nanotubes (CNTs). However, it is still a great challenge to realize size-controllable giant carbon macrocycles. Herein, a tunable synthesis of curved nanographene-based giant π-extended macrocyclic rings (CHBC[n]s; n=8, 6, 4), as finite models of armchair CNTs, is reported. Among them, CHBC[8] contains 336 all-carbon atoms and is the largest cyclic conjugated molecular CNT segment ever reported. CHBC[n]s were systematically characterized by various spectroscopic methods and applied in photoelectrochemical cells for the first time. This revealed that the proton chemical shifts, fluorescence, and electronic and photoelectrical properties of CHBC[n]s are highly dependent on the macrocycle diameter. The tunable bottom-up synthesis of giant macrocyclic rings could pave the way towards large π-extended diameter- and chirality-specific CNT segments.