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In the spirit of pursuing collaborative research at the interface of chemistry and materials science for engineering cyclophane‐based functional systems, the journey from molecules to materials and a portion of the accomplishments exploring technologically‐relevant small‐molecule organic emitters, polymer thin films, and supra‐sensing through supramolecular host‐guest interactions (molecular self‐assembly) is shared. This report highlights diverse research trajectories and the importance of active collaboration within the chemistry community. It is also intended to serves young scientists who are committed to research in interdisciplinary domains. This inspires fostering global research networks and promoting industrial−academic symbiosis that bring innovations to the education environment and curriculum by sharing mutual experiences, knowledge, and specialized skills which may cut across several inter‐related disciplines. [ABSTRACT FROM AUTHOR]

The prototypical example of a (cyclo)phane, [2.2]paracyclophane (PCP), has proven to be a versatile stereogenic moiety within the design of circularly polarized thermally activated delayed fluorescence (CP‐TADF) emitters; however, the exploration of other cyclophanes within CP‐TADF emitter design has been largely neglected. Here, a comparative study of the photophysical and optoelectronic properties of two cyclophane emitters, (1,7)tBuCzpPhTrz and its isomer (1,4)tBuCzpPhTrz, is presented. The carbazolophane‐triazine compound (1,7)tBuCzpPhTrz, obtained via an unprecedented intramolecular rearrangement, is the first example of a planar chiral TADF emitter deviating from the PCP scaffold. Significant geometrical change of the enclosed carbazole in (1,7)tBuCzp results in an attenuation of the donor strength, while the merits of rigidity and steric bulk remain. In particular, the full width at half maximum (FWHM) of the photoluminescence spectrum in toluene of (1,7)tBuCzpPhTrz is reduced by 34% and blue‐shifted by 20 nm compared to that of (1,4)tBuCzpPhTrz. In doped films, the compounds reach high photoluminescence quantum yields (ΦPL) of 91 and 81%, respectively. The chiroptical properties reveal dissymmetry factors |gPL| of up to 5 × 10−4. These results demonstrate the impact of the cyclophane for the development of CP‐TADF materials and add to the currently limited scope of available planar chiral donors. [ABSTRACT FROM AUTHOR]

The development and integration of cyclophanes into future functional materials require a detailed understanding of the physicochemical principles that underlie their properties, phase behavior, and in particular the relationship between structure and function. Here, electrochemically switchable crystallization of a ferrocene‐bearing 3D Janus tecton (M‐Fc) at the interface between highly oriented pyrolytic graphite (HOPG) and an electrolyte solution is demonstrated. The M‐Fc adlayer is successfully visualized under both ambient and electrochemical conditions using scanning tunneling microscopy. Voltammetric measurements show a surface‐confined redox process for the M‐Fc modified surface that drives the phase transition between a visible 2D ordered linear phase (M‐Fc0, with ferrocene in the neutral state) and an invisible gas‐like adsorption layer with high mobility when ferrocene is oxidized, M‐Fc+, and a "square scheme" mechanism explains the data. Analogous experiments in a ferrocene‐free tecton adlayer show no phase transition and confirm that the dynamics in M‐Fc are redox‐driven. On‐surface 3D nanoarchitectures are also demonstrated by forming inclusion complexes between M‐Fc and β‐cyclodextrin and device behavior through electrochemical scanning tunneling spectroscopy (STS). These results showcase the functional potential of this class of cyclophanes, which can find use in actuators, optical crystals, and other smart materials. [ABSTRACT FROM AUTHOR]

For over 60 years, cyclophanes have inspired the design of novel molecular architectures of different sizes and geometries, unleashing significant advances in supramolecular chemistry and also in biomedical and materials sciences. Reported cyclophanes are countless and more complex molecular structures continue to be spawned. Herein, the study classifies cyclophanes into different families to emphasize and feature their structure‐properties relationships. While neutral cyclophanes have attracted more attention owing to their solid‐state physical properties, water‐soluble anionic cyclophanes have been explored predominantly in drug delivery. In the broad family of cationic cyclophanes, viologen‐based cyclophanes (VBCs) are widely investigated for designing molecular interlocked molecules (MIMs), molecular switches, and machines owing to their unique electrochemical properties. Despite decades of ground‐breaking research in academia, controlling the cationic cyclophanes and MIMs solid‐state structures is still a limiting factor when it comes to introducing them into functional materials. Here, the study draws attention to some current challenges in cyclophane chemistry from a materials sciences perspective and highlights processes that, if overcome, would lead to cyclophanes producing transformational materials. It is envisioned that zwitterionic VBCs can have a seminal impact on host–guest chemistry, MIMs, molecular machines, and supramolecular tessellations, which can pave the way toward next‐generation technologies. [ABSTRACT FROM AUTHOR]

This work reports the synthesis and self‐assembly of perylene diimide (PDI)‐containing macrocycles designed for facile and high‐throughput production of shape‐persistent, macrocyclic organic electronic materials. Specifically, utilizing dynamic covalent chemistry (DCvC), this work showcases ditopic thiols can be utilized as building blocks toward 3D materials with defined porosity, low‐lying unoccupied molecular orbitals, and intrinsic fluorescence. The PDI disulfide‐linked macrocycles are generated in a single step from the thiolic building block to yield dimeric through pentameric assemblies in overall 95% combined yield; moreover, following self‐assembly, the disulfide ensemble is sulfur extruded to the more kinetically stable thioether in 79% combined yield. The modular design suggests these methods can be used to easily self‐assemble other electronically active precursors for utility in porous macrocyclic materials where stepwise pathways may be laborious and/or low yielding. [ABSTRACT FROM AUTHOR]

In tetracene, the energies of the lowest singlet excited state and twice that of the lowest triplet excited state are similar, allowing both down‐conversion (i.e., singlet fission, SF) and up‐conversion (i.e., triplet‐triplet annihilation up‐conversion, TTA‐UC) processes. Through‐space and through‐bond contributions to the inter‐tetracene coupling in purposefully designed oligomers play a crucial role in determining which of the two processes dominates. In this work, the focus is exclusively on SF in newly synthesized oligo‐tetracenes linked by conjugated [2.2]paracyclophane (PCP) building blocks. By choosing different PCP substitution patterns and by varying the degree of substitution the inter‐tetracene couplings are addressed. An independent variable is connecting the tetracences to the PCP at different positions to alter the through‐bond and through‐space coupling of the resulting oligo‐tetracenes. The novel oligo‐tetracenes are investigated by means of steady‐state and time‐resolved absorption and fluorescence spectroscopies with respect to the initial events of SF, that is, the transformation of a singlet excited state into a correlated triplet pair state. Briefly, through‐space couplings are profoundly weaker than through‐bond couplings that enable the correlated triplet pair state formation. If interactions are through‐space, correlated triplet pair state formation is turned off, while it is turned on if through‐bond interactions are operative. [ABSTRACT FROM AUTHOR]

Many of the functions and features of practically useful materials are the province of molecular‐level chemistry and their modulation at different length‐scale. This report illustrates the molecular‐level chemistry behind functions and features of the [2.2]paracyclophane‐based materials with a particular focus on the most recent explorations on through‐space conjugated small‐molecule organic emitters, π‐stacked macrocyclic molecules and polymers, poly(p‐phenylenevinylene)s featuring well‐defined donor‐acceptors sequence control, and surface engineering of technologically‐relevant parylenes that finds broad applications across the field of chemical science and technology. This report largely deals with the potential and opportunities associated with molecular features and functions of planar chirality, conformational behaviors, strain‐induced non‐planarity of the aromatics, the profound impacts of through‐space conjugation and π‐electron interactions/delocalization on optoelectronic properties of the π‐conjugated organic emitters, polymers and extended structures consisting of cyclophanes. A special focus is put on the concept of supramolecular polymers using chemically‐programmed chiral cyclophanes via non‐covalent stacking and controlled conformational arrangements. Illustrating cyclophane as precursors/monomers and fabrication strategies for their incorporation in structurally‐controlled (poly(p‐xylylene)s formed via chemical vapor deposition polymerization and post‐deposition fabrication for interface engineering is described. Demonstrating a rather different approach of electronically‐dictated ring‐opening metathesis polymerization employing strained cyclophane‐diene precursors that generate conjugated poly(p‐phenylenevinylene)s with well‐defined (i.e., low dispersity) and donor‐acceptor sequence control is also discussed. This report will serve as an indispensable one‐stop reference for organic, and polymer chemists, as well as material scientists working with cyclophanes for research innovations. [ABSTRACT FROM AUTHOR]

The synthesis of a novel large type double-layered cyclophanes has been successfully accomplished by free radical coupling reaction with the bis(N-alkylene benzothiazolium) dibromide salts as their important synthetic intermediates. The structures of the two-layered cyclophanes and the synthetic intermediates have been elucidated based on the NMR data and X-ray structural analysis, respectively. The two-layered cyclophanes consist of two different geometries, anti-two cyclic lactam amide rings inside and two bridges of disulfide bonds outside, which are unique and novel structures. Their physical properties were investigated by UV–Vis and redox potential, too. [ABSTRACT FROM AUTHOR]

Supramolecular recognition of nucleobases and short sequences is an emerging research field focusing on possible applications to treat many diseases. Controlling the affinity and selectivity of synthetic receptors to target desired nucleotides or short sequences is a highly challenging task. Herein, we elucidate the effect of substituents in the phenyl ring of the anthracene‐benzene azacyclophane on the recognition of nucleoside triphosphates (NTPs) and double‐stranded DNA. We show that introducing phenyl rings increases the affinity for NTPs 10‐fold and implements groove and intercalation binding modes with double‐stranded DNA. NMR studies and molecular modeling calculations support the ability of cyclophanes to encapsulate nucleobases as part of nucleotides. [ABSTRACT FROM AUTHOR]

We present an improved and convenient synthesis of [2.2]paracyclophane‐imidazoline N,O‐ligands with central and planar chirality in seven steps starting from [2.2]paracyclophane. The utility of these ligands in organozinc additions to aldehydes is described. The asymmetric ethylation of aldehydes proceeded with enantioselectivities of up to 97 % ee, while the asymmetric arylation of aldehydes gave up to 95 % ee (R) and 82 % ee (S) using (S,S,SP)‐UCD‐Imphanol and (S,S,RP)‐UCD‐Imphanol, respectively. [ABSTRACT FROM AUTHOR]

Planar‐chiral skeletons widely exist in natural products, bioactive compounds, and other functional molecules. Although significant progress has been made in the field of asymmetric synthesis of centrally or axially chiral molecules over the past years, enantioselective constructing of planar chirality is still a big obstacle and numerous efforts have been made in this field. Previous works have mainly focused on the assembly of planar‐chiral [2,2]‐paracyclophanes and metallocenes. This Minireview describes recent advancements in asymmetric catalytic synthesis of planar‐chiral macrocycles, including ansa chain construction, plane formation and asymmetric transformation strategies. It is anticipated that this Minireview will sever as a source of inspiration for developing new unconventional procedures for access to planar‐chiral skeletons. [ABSTRACT FROM AUTHOR]

In the present study, conformations and aromaticity of seventeen [13], [23] and [33] double-stranded cyclophanes composed of three benzene moieties were investigated at B3LYP level of density functional theory. The stability of these conformers is different depending on the type of cycloalkane-like cycles formed by (CH2) n bridges and the peripheral benzene rings, and also the curvature of the latter. In [13] cyclophane, this leads to only one conformer containing puckered cyclobutane-like cycle, at an angle of about 37◦. In comparison, in cyclophanes [23] and [33], the corresponding cycles are cyclohexane-like and cyclooctane-like, respectively. While conformer 2a having TB-like cycles is the most stable member of the [23] family, of eight ground-state conformers obtained for [33], 3a with two Chair-Chair-like and one Twist-Chair-like cycles is the most stable one, and 3h with three Twist-Boat-like cycles being 6.5 kcal higher in energy than the former is the least stable member of series. In addition to the conformational analysis, the aromaticity of the series has been assessed using different indexes, including magnetic criteria nucleus-independent chemical shifts (NICS-based) at the cage and at the ring centers, HNMR chemical shift, Magnetic Susceptibility, HOMA and relative energy (RE). [ABSTRACT FROM AUTHOR]

π‐Conjugated chiral nanorings with intriguing electronic structures and chiroptical properties have attracted considerable interests in synthetic chemistry and materials science. We present the design principles to access new chiral macrocycles (1 and 2) that are essentially built on the key components of main‐group electron‐donating carbazolyl moieties or the π‐expanded aza[7]helicenes. Both macrocycles show the unique molecular conformations with a (quasi) figure‐of‐eight topology as a result of the conjugation patterns of 2,2',7,7'‐spirobifluorenyl in 1 and triarylamine‐coupled aza[7]helicene‐based building blocks in 2. This electronic nature of redox‐active, carbazole‐rich backbones enabled these macrocycles to be readily oxidized chemically and electrochemically, leading to the sequential production of a series of positively charged polycationic open‐shell cyclophanes. Their redox‐dependent electronic states of the resulting multispin polyradicals have been characterized by VT‐ESR, UV/Vis‐NIR absorption and spectroelectrochemical measurements. The singlet (ΔES‐T=−1.29 kcal mol−1) and a nearly degenerate singlet‐triplet ground state (ΔES−T(calcd)=−0.15 kcal mol−1 and ΔES−T(exp)=0.01 kcal mol−1) were proved for diradical dications 12+2⋅ and 22+2⋅, respectively. Our work provides an experimental proof for the construction of electron‐donating new chiral nanorings, and more importantly for highly charged polyradicals with potential applications in chirospintronics and organic conductors. [ABSTRACT FROM AUTHOR]

Although the Perkin reaction has been successful in producing ester-substituted conjugated macrocycles with four or six building blocks, macrocycles composed of only two elements remained elusive until now. Through the development of a building block derived from phenanthrene with two glyoxylic acid substituents in a pincer-like arrangement, formation of a two-block macrocycle was induced when paired with a complementary phenylenediacetic acid unit. The addition of ether functions to the phenanthrene building block not only improved the yields, but led to macrocycles with push--pull geometries. Photocyclisation of the resulting cyclophanes efficiently yield tetra- and hexasubstituted coronenes. [ABSTRACT FROM AUTHOR]

π–π interactions are among the most important intermolecular interactions in supramolecular systems. Here we determine experimentally a universal parameter for their strength that is simply based on the size of the interacting contact surfaces. Toward this goal we designed a new cyclophane based on terrylene bisimide (TBI) π‐walls connected by para‐xylylene spacer units. With its extended π‐surface this cyclophane proved to be an excellent and universal host for the complexation of π‐conjugated guests, including small and large polycyclic aromatic hydrocarbons (PAHs) as well as dye molecules. The observed binding constants range up to 108 M−1 and show a linear dependence on the 2D area size of the guest molecules. This correlation can be used for the prediction of binding constants and for the design of new host–guest systems based on the herewith derived universal Gibbs interaction energy parameter of 0.31 kJ/molÅ2 in chloroform. [ABSTRACT FROM AUTHOR]

Tetracene cyclophanes: a series of cyclic tetracene dimers bridged by two flexible ethylene glycol units demonstrated enhanced intramolecular singlet fission through through-space orientations by suppressing the H-type excited complex. [ABSTRACT FROM AUTHOR]

An efficient catalytic asymmetric electrophilic sulfenylation reaction for the synthesis of planar‐chiral sulfur‐containing cyclophanes has been developed for the first time. This was achieved by using a new Lewis base catalyst and a new ortho‐trifluoromethyl‐substituted sulfenylating reagent. Using the substrates with low rotational energy barrier, the transformation proceeded through a dynamic kinetic resolution, and the high rotational energy barrier of the substrates allowed the reaction to undergo a kinetic resolution process. Meanwhile, this transformation was compatible with a desymmetrization process when the symmetric substrates were used. Various planar‐chiral sulfur‐containing cyclophanes were readily obtained in moderate to excellent yields with moderate to excellent enantioselectivities (up to 97 % yield and 95 % ee). This approach was used to synthesize pharmaceutically relevant planar‐chiral sulfur‐containing molecules. Density functional theory calculations showed that π‐π interactions between the sulfenyl group and the aromatic ring in the substrate play a crucial role in enantioinduction in this sulfenylation reaction. [ABSTRACT FROM AUTHOR]

Cyclic peptides with cyclophane linkers are an attractive compound type owing to the fine‐tuned rigid three‐dimensional structures and unusual biophysical features. Cytochrome P450 enzymes are capable of catalyzing not only the C−C and C−O oxidative coupling reactions found in vancomycin and other nonribosomal peptides (NRPs), but they also exhibit novel catalytic activities to generate cyclic ribosomally synthesized and post‐translationally modified peptides (RiPPs) through cyclophane linkage. To discover more P450‐modified multicyclic RiPPs, we set out to find cryptic and unknown P450‐modified RiPP biosynthetic gene clusters (BGCs) through genome mining. Synergized bioinformatic analysis reveals that P450‐modified RiPP BGCs are broadly distributed in bacteria and can be classified into 11 classes. Focusing on two classes of P450‐modified RiPP BGCs where precursor peptides contain multiple conserved aromatic amino acid residues, we characterized 11 novel P450‐modified multicyclic RiPPs with different cyclophane linkers through heterologous expression. Further mutation of the key ring‐forming residues and combinatorial biosynthesis study revealed the order of bond formation and the specificity of P450s. This study reveals the functional diversity of P450 enzymes involved in the cyclophane‐containing RiPPs and indicates that P450 enzymes are promising tools for rapidly obtaining structurally diverse cyclic peptide derivatives. [ABSTRACT FROM AUTHOR]

Planar‐chiral cyclophanes have received increasing attention for drug discovery and catalyst design. However, the catalytically asymmetric synthesis of planar‐chiral cyclophanes has been a longstanding challenge. We describe the first Pd(II)‐catalyzed enantioselective C−H olefination of prochiral cyclophanes. The low rotational barrier of less hindered benzene ring in the substrates allows the reaction to proceed through a dynamic kinetic resolution. This approach exhibits broad substrate scope, providing the planar‐chiral cyclophanes in high yields (up to 99 %) with excellent enantioselectivities (up to >99 % ee). The ansa chain length scope studies reveal that the chirality of the cyclophanes arises from the bond rotation constraint of the benzene ring around the macrocycle plane, rather than the C−N axis. The C−H activation approach is also applicable to the late‐stage modification of bioactive molecules and pharmaceuticals. [ABSTRACT FROM AUTHOR]

A large, strained (SE=44.2 kcal/mol) and conformationally flexible mixed cyclophane of pyridine and teropyrene was synthesized using two intramolecular Wurtz coupling reactions and an unprecedented Scholl reaction between the unreactive 2 positions of the pyrene systems in a triply bridged pyrenophane. Protonation of the pyridine unit results in a greatly enhanced preference for nesting in the cavity of the highly bent teropyrene system (θcalc=162.6°) and emergence of a charge transfer absorption band (λmax=592 nm) due to a long range (5.0–5.5 Å), through‐space intramolecular transition between the teropyrene and pyridinium units, which does not exist in the neutral cyclophane. [ABSTRACT FROM AUTHOR]

We realized a simple approach involving the 1,6‐conjugate addition (regioselective thiolation) of para‐quinone methides (p‐QMs) with easily available thio‐based nucleophiles. Through ring‐closing metathesis (RCM), this procedure delivered a variety of para‐ and meta‐thiaoxacyclophanes as E‐isomers in good yields. A simple thiol‐free one‐pot approach is reported for the direct synthesis of sulfides and sulfones under green reaction conditions without the use of any metal catalysts. Low‐cost and easily accessible compounds such as p‐QMs and benzyl bromides are used as starting materials in the presence of potassium thioacetate (PTA) and Oxone®. Novel thiaoxacyclophanes were assembled in three simple steps including conjugate addition of PTA, Grignard addition, and RCM sequence. [ABSTRACT FROM AUTHOR]

Cyclotribenzylenes (CTBs) combining carbonitrile (−CN) and alkyne (−C2H) substituents were synthesized as racemic mixtures and resolved by HPLC on chiral stationary phases. Two of these compounds were used to prepare platinum‐bridged CTB dimers, in which PtII is bound to the CTBs via Pt−alkynyl bonds in cis configuration. The organometallic complexes were examined by mass spectrometry and NMR spectroscopy, which indicated that they were obtained as mixtures of diastereoisomers (a meso or syn form and a pair of chiral or anti forms) when racemic CTBs were used. Enantiomerically pure complexes were prepared from resolved CTBs, which allowed us to distinguish the NMR signals of the chiral and meso forms in the diastereoisomeric mixtures. In certain conditions, the platinum complexes played the role of a pincer π‐alkynyl ligand for Cu(I) coming from the copper iodide used as a synthetic auxiliary. The Cu+ cations could be easily removed by treatment with NaCN, affording the mononuclear bis‐cyclotribenzylene complexes. These compounds failed to lead to metallo‐cryptophanes by coordination of two [M(dppp)]2+ complex subunits (M=Pd, Pt; dppp=1,3‐bis(diphenylphosphino)propane), each to two carbonitrile substituents belonging to different CTBs, pointing to the superiority of the one pot self‐assembly processes for the preparation of metallo‐cryptophanes. [ABSTRACT FROM AUTHOR]

Abstract An azo-clamped nanoscale bichromophoric cyclophane is synthesized by the intramolecular Pd(II)-catalyzed coupling of the corresponding bisacetylenic precursor. The two azo moieties in the latter can adopt cis and trans configurations. Thin-layer chromatography shows only two spots, and by scanning tunneling microscopy the trans/trans and cis/cis isomers are found. The final cyclophane does not show any switching behavior at all, but dense and wide structures are visualized after adsorption to highly oriented pyrolytic graphite. Photophysical investigations of the cyclophane show that most of the fluorescence is quenched, most likely due to the azo clamp. However, bright molecules show nearly perfect single-photon emission, meaning that efficient energy transfer between the two chromophores takes place within the molecule.

Crystal packing and chromophore communication are key parameters for the performance and functionality of many applications related to light‐energy harvesting and conversion. However, obtaining crystals of flexible and very soluble structures is troublesome. Nevertheless, a crystal structure of a highly flexible perylene‐3,4 : 9,10‐tetracarboxylic acid bisimide (PBI) cyclophane was obtained and analysed to compare the chromophore arrangement in the solid state with theconfiguration in solution as well as with calculated structures. The crystal structure exhibits an intra‐ and intermolecular slip‐stack arrangement of the heterochiral PBI units, forming a unique one‐dimensional π‐stacking supramolecular polymer‐like structure. These findings emphasize that the unique solid‐state arrangement of the chromophores cannot be easily predicted by elaborate studies in solution or by theoretical calculations. Furthermore, it features the importance of controlling the crystal packing to enable specific applications based on multiexciton generation processes where the spatial dependence and relative orientation of the chromophores are decisive parameters. [ABSTRACT FROM AUTHOR]

Water‐soluble small organic photothermal agents (PTAs) over NIR‐II biowindow (1000–1350 nm) are highly desirable, but the rarity greatly limits their applications. Based on a water‐soluble double‐cavity cyclophane GBox‐44+, we report a class of host–guest charge transfer (CT) complexes as structurally uniform PTAs for NIR‐II photothermal therapy. As a result of its high electron‐deficiency, GBox‐44+ can bind different electron‐rich planar guests with a 1 : 2 host/guest stoichiometry to readily tune the CT absorption band that extends to the NIR‐II region. When using a diaminofluorene guest substituted with an oligoethylene glycol chain, the host–guest system realized both good biocompatibility and enhanced photothermal conversion at 1064 nm, and was then exploited as a high‐efficiency NIR‐II PTA for cancer cell and bacterial ablation. This work broadens the potential applications of host–guest cyclophane systems and provides a new access to bio‐friendly NIR‐II photoabsorbers with well‐defined structures. [ABSTRACT FROM AUTHOR]

Herein we present a systematic study of the influence of different alkyl chains in malonyl ester fullerene adducts with [10]cycloparaphenylene ([10]CPP]) and a tert‐butyl (tBu) ester‐substituted [10]CPP analogue. The association constants between the nanoring hosts and the fullerene guests were determined by fluorescence quenching experiments. The trends in association were rationalized by an interplay of repulsion arising from an extended volume and London dispersion as an attractive counterpart. [ABSTRACT FROM AUTHOR]

First representatives of chiral ferrocenophanes have been synthesized from bispidines. Their struc-ture in solution has been found to be similar to the structure of previously reported achiral ferrocenophane. [ABSTRACT FROM AUTHOR]

Abstract Two [60]fullerene dumbbell-like molecules with a single or double perylene-3,4,9,10-tetracarboxylic acid bisimide (PBI) linker were synthesized to study the structural and photophysical properties in addition to the complex formation with [10]cycloparaphenylene ([10]CPP). Due to their special optical properties, it is possible to describe the complexation using conventional spectroscopic methods such as NMR and fluorescence. However, isothermal titration calorimetry (ITC) was used to complete the analysis of the bis-pseudorotaxane formation by investigating the binding stoichiometries as well as the thermodynamic and kinetic parameters. It was observed that the PBI bridges do not inhibit the complexation with [10]CPP, giving rise to the formation of 1 : 1 and 1 : 2 complexes in o-dichlorobenzene with affinities of around 105 · M−1, similar to the [10]CPP⊃C60 reference system. A novel global analysis by combination of data sets from different techniques allowed us to follow the species distribution very precisely. ITC has proven to be a very powerful method for studying the complexation between fullerene derivatives and strained carbon nanohoops, which provides not only binding affinities and stoichiometries, but also all thermodynamic and kinetic parameters of the bis-pseudorotaxane formation. These results are of significant interest for the investigation of fullerene complexes in supramolecular chemistry and for their future applications in semiconductors and optoelectronics.

In this study, 28-membered macrocyclic 1,5(1,5)-di(1,5-diaza-3,7-diphosphacyclooctana)-2,4,6,8(1,4)-tetrabenzenacyclooctaphane were synthesized by condensation of pyridinephosphine, paraformaldehyde, and primary diamines (bis(4-aminophenyl)methane or -sulfide. The first representatives of binuclear copper(I) complexes of P,N-containing cyclophanes with two 1,5-diaza-3,7-diphosphacyclooctane rings incorporated into a macrocyclic core and intracavity location of unusual, developed angle Cu2I moiety were obtained. The structure of one complex was established by X-ray diffraction analysis. The complexation led to a slight distortion of the cyclophane conformations. [ABSTRACT FROM AUTHOR]

The tetracationic cyclophane, cyclobis(paraquat‐p‐phenylene), also known as the little blue box, constitutes a modular receptor that has facilitated the discovery of many host–guest complexes and mechanically interlocked molecules during the past 35 years. Its versatility in binding small π‐donors in its tetracationic state, as well as forming trisradical tricationic complexes with viologen radical cations in its doubly reduced bisradical dicationic state, renders it valuable for the construction of various stimuli‐responsive materials. Since the first reports in 1988, the little blue box has been featured in over 500 publications in the literature. All this research activity would not have been possible without the seminal contributions carried out by Siegfried Hünig, who not only pioneered the syntheses of viologen‐containing cyclophanes, but also revealed their rich redox chemistry in addition to their ability to undergo intramolecular π‐dimerization. This Review describes how his pioneering research led to the design and synthesis of the little blue box, and how this redox‐active host evolved into the key component of molecular shuttles, switches, and machines. [ABSTRACT FROM AUTHOR]

We synthesized planar chiral cyclophanes with multiple pairs of helical conformations that were generated by twisting at the interlayer. Three- and four-layer cyclophanes preferred a homochiral form with a single sense of twisting through intramolecular transmission of planar chirality. Alternatively, a heterochiral form was dominant in a two-layer cyclophane consisting of two achiral planes that were stacked orthogonally. [ABSTRACT FROM AUTHOR]

The intricate frameworks of paracyclophanes are an important target for synthesis since they are found in various chiral auxiliaries, solar cells, high‐performance plastics, pharmaceuticals, and molecular machines. Whereas numerous methods exist for the preparation of symmetric paracyclophanes, protocols for the efficient synthesis of strained asymmetric scaffolds are limited. Here we report a remarkably simple photochemical route to strained [3.2]paracyclophanes starting from readily available educts. By way of NMR and X‐ray analyses, we discovered that UV‐irradiation of an aromatic carboxylic ester tethered to a toluene moiety leads to the intramolecular formation of a new C−C bond, with loss of an alcohol. A systematic evaluation of the reaction conditions and substituents, as well as radical starter and triplet quenching experiments, point to a reaction mechanism involving an excited triplet state and hydrogen atom transfer. The new method proved to be robust and versatile enabling the synthesis of a range of cyclophanes with different substitutions, including an unusual diastereoisomer with two planar chiral centers, and thus proved to be a valuable addition to the synthetic toolbox. [ABSTRACT FROM AUTHOR]

The introduction of electron‐donating, bridging guanidinate substituents in diborane(4) compounds allows the synthesis of a variety of new cationic diborane(4) compounds. In this work, strategies for the directed synthesis of cationic di‐ and tetraboron compounds are presented, leading to the synthesis and complete characterization of several new compounds with distinct structural motifs, all exhibiting BII atoms directly bound to each other. Hence, we report on tetracationic donor‐acceptor cyclophanes with diboron donor linkers and organic π‐acceptor units, on paddlewheel‐type cationic diboranes, and on unsymmetrically‐substituted monocationic diboranes. [ABSTRACT FROM AUTHOR]

Mechanochromic mechanophores are reporter molecules that indicate mechanical events through changes of their photophysical properties. Supramolecular mechanophores in which the activation is based on the rearrangement of luminophores and/or quenchers without any covalent bond scission, remain less well investigated. Here, we report a cyclophane‐based supramolecular mechanophore that contains a 1,6‐bis(phenylethynyl)pyrene luminophore and a pyromellitic diimide quencher. In solution, the blue monomer emission of the luminophore is largely quenched and a faint reddish‐orange emission originating from a charge‐transfer (CT) complex is observed. A polyurethane elastomer containing the mechanophore displays orange emission in the absence of force, which is dominated by the CT‐emission. Mechanical deformation causes a decrease of the CT‐emission and an increase of blue monomer emission, due to the spatial separation between the luminophore and quencher. The ratio of the two emission intensities correlates with the applied stress. [ABSTRACT FROM AUTHOR]

This paper reviews the most stable conformation of crystalline three-dimensional cyclophane (CP) achieved by self-assembling based on changing the type of aromatic compound or regulating the type and number of bridging groups. [3n]cyclophanes (CPs) were reported to form supramolecular compounds with bind organic, inorganic anions, or neutral molecules selectively. [3n]cyclophanes ([3n]CPs) have stronger donor capability relative to compound [2n]cyclophanes ([2n]CPs), and it is expected to be a new type of electron donor for the progress of fresh electron conductive materials. The synthesis, conformational behavior, and properties of crystalline multi-bridge rings are summarized and discussed. [ABSTRACT FROM AUTHOR]

Here, we report an approach to the synthesis of highly charged enantiopure cyclophanes by the insertion of axially chiral enantiomeric binaphthyl fluorophores into the constitutions of pyridinium‐based macrocycles. Remarkably, these fluorescent tetracationic cyclophanes exhibit a significant AIE compared to their neutral optically active binaphthyl precursors. A combination of theoretical calculations and time‐resolved spectroscopy reveal that the AIE originates from limited torsional vibrations associated with the axes of chirality present in the chiral enantiomeric binaphthyl units and the fine‐tuning of their electronic landscape when incorporated within the cyclophane structure. Furthermore, these highly charged enantiopure cyclophanes display CPL responses both in solution and in the aggregated state. This unique duality of AIE and CPL in these tetracationic cyclophanes is destined to be of major importance in future development of photonic devices and bio‐applications. [ABSTRACT FROM AUTHOR]

Two of nature's recurring binding motifs in metalloproteins are the CxxxCxxC motif in radical SAM enzymes and the 2-His-1-carboxylate motif found both in zincins and α-ketoglutarate and non-haem iron enzymes. Here we show the confluence of these two domains in a single post-translational modifying enzyme containing an N-terminal radical S-adenosylmethionine domain fused to a C-terminal 2-His-1-carboxylate (HExxH) domain. The radical SAM domain catalyses three-residue cyclophane formation and is the signature modification of triceptides, a class of ribosomally synthesized and post-translationally modified peptides. The HExxH domain is a defining feature of zinc metalloproteases. Yet the HExxH motif-containing domain studied here catalyses β-hydroxylation and is an α-ketoglutarate non-haem iron enzyme. We determined the crystal structure for this HExxH protein at 2.8 Å, unveiling a distinct structural fold, thus expanding the family of α-ketoglutarate non-haem iron enzymes with a class that we propose to name αKG-HExxH. αKG-HExxH proteins represent a unique family of ribosomally synthesized and post-translationally modified peptide modifying enzymes that can furnish opportunities for genome mining, synthetic biology and enzymology., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Aromatic units bring special features to supramolecular receptors when the challenge of binding and release of CO2 is being addressed. Recent examples arising from calixarenes, pillararenes and cyclophanes are discussed in this review. The abilities of these systems to spatially organize metal coordination, hydrogen bonding or hydrophobic interactions for the purpose of CO2 binding are pointed out. Consequences for sensing and catalytic reactions are also highlighted.

We present a facile synthetic route toward a novel series of imidazolinyl‐[2.2]paracyclophanol (UCD‐Imphanol) ligands possessing central and planar chirality. Both sets of diastereomeric ligands were successfully purified by column chromatography. The preliminary application of this family of ligands showed excellent activities in the asymmetric Zn‐catalyzed azomethine ylide cycloaddition. Enantioenriched pyrrolidines, in a substrate scope of 20 examples, were accessed in high levels of endo/exo ratios (up to >99/1) and enantioselectivities (up to >99 % ee) with excellent yields (up to 99 %) by using (S,S,SP)‐UCD‐Imphanol/(S,S,RP)‐UCD‐Imphanol, respectively. [ABSTRACT FROM AUTHOR]

Multichromophoric macrocycles and cyclophanes are important supramolecular architectures for the elucidation of interchromophoric interactions originating from precise spatial organization. Herein, by combining an axially chiral binaphthol bisimide (BBI) and a bay‐substituted conformationally labile twisted perylene bisimide (PBI) within a cyclophane of well‐defined geometry, we report a chiral PBI hetero‐cyclophane (BBI‐PBI) that shows intramolecular energy and solvent‐regulated chirality transfer from the BBI to the PBI subunit. Excellent spectral overlap and spatial arrangement of BBI and PBI lead to efficient excitation energy transfer and subsequent PBI emission with high quantum yield (80–98 %) in various solvents. In contrast, chirality transfer is strongly dependent on the respective solvent as revealed by circular dichroism (CD) spectroscopy. The combination of energy and chirality transfer affords a bright red circularly polarized luminescence (CPL) from the PBI chromophore by excitation of BBI. [ABSTRACT FROM AUTHOR]

Cyclophanes are a fundamentally interesting class of compounds that host a wide range of unique and emergent properties. However, synthesis of complex and/or functionalized cyclophanes can often suffer from harsh reaction conditions, long reaction times, and sometimes low yields using stepwise methods. We have previously reported an efficient, high‐yielding, metalloid‐directed self‐assembly method to prepare disulfide, thioether, and hydrocarbon cyclophanes and cages that feature mercaptomethyl‐arenes as starting materials. Herein, we report the synthesis of 21 new disulfide and thioether assemblies that expand this high yielding self‐assembly method to a wide breadth of macrocycles and cages with diverse structures. Remarkably, the high‐yielding, efficient syntheses still proceed under dynamic covalent control using electron‐deficient, heteroaryl, cycloalkyl, spiro, and even short alkenyl/alkynyl substrates. [ABSTRACT FROM AUTHOR]

With the serendipitous discovery of crown ethers by Pedersen more than half a century ago and the subsequent introduction of host–guest chemistry and supramolecular chemistry by Cram and Lehn, respectively, followed by the design and synthesis of wholly synthetic cyclophanes—in particular, fluorescent cyclophanes, having rich structural characteristics and functions—have been the focus of considerable research activity during the past few decades. Cyclophanes with remarkable emissive properties have been investigated continuously over the years and employed in numerous applications across the field of science and technology. In this Review, we feature the recent developments in the chemistry of fluorescent cyclophanes, along with their design and synthesis. Their host–guest chemistry and applications related to their structure and properties are highlighted. [ABSTRACT FROM AUTHOR]

Heat-induced solid-state decarboxylation of tetra(malonatemethylene) based cyclophane leads to its tetra(2-carboxyethyl) derivative in quantitative yield. This reaction provides more thermostable substance compared to the product of the same cyclophane decarboxylation in solution. The studied cyclophanes have been characterized by means of simultaneous thermal analysis involving thermogravimetry, differential scanning calorimetry, and mass spectrometry of evolved gases as well as fast scanning calorimetry, a method preferable to investigate the compounds with relatively low thermal stability. [ABSTRACT FROM AUTHOR]

Superphane, i.e., [2.2.2.2.2.2](1,2,3,4,5,6)cyclophane, is a very convenient molecule in studying the nature of guest⋯host interactions in endohedral complexes. Nevertheless, the presence of as many as six ethylene bridges in the superphane molecule makes it practically impossible for the trapped entity to escape out of the superphane cage. Thus, in this article, I have implemented the idea of using the superphane derivatives with a reduced number of ethylene linkers, which leads to the [2 n ] cyclophanes where n < 6 . Seven such cyclophanes are then allowed to form endohedral complexes with noble gas (Ng) atoms (He, Ne, Ar, Kr). It is shown that in the vast majority of cases, the initially trapped Ng atom spontaneously escapes from the cyclophane cage, creating an exohedral complex. This is the best proof that the Ng⋯cyclophane interaction in endohedral complexes is indeed highly repulsive, i.e., destabilizing. Apart from the 'sealed' superphane molecule, endohedral complexes are only formed in the case of the smallest He atom. However, it has been shown that in these cases, the Ng⋯cyclophane interaction inside the cyclophane cage is nonbonding, i.e., repulsive. This highly energetically unfavorable effect causes the cyclophane molecule to 'swell'. [ABSTRACT FROM AUTHOR]

Engineering novel micro‐/nanoscale systems and devices based on supramolecular assembly has tremendous potential from diverse applications perspective. However, controlling the size, shape, spatial arrangements, and hierarchical transcription by a dimensional organizing principle (1D–3D arrangement) without the help of templates remains a challenging task. In this vein, a recent study by Oki and colleagues reporting the stacking of chiral cyclophanes via intermolecular non‐covalent interactions for crafting synchronous microcrystalline 3D chiral vessels with controlled conformational arrangements represents a truly remarkable illustration of molecular engineering. The microvessels bear stereocontrolled skeletal morphology, recognize stereoisomers and serve as containers to accommodate microcrystals, polymer particles, and fluorescent dyes. The full application scope of this fascinating research is far beyond non‐covalent interactions, supramolecular self‐assembly, and crystal engineering. [ABSTRACT FROM AUTHOR]

Perylene diimides (PDIs), a well‐studied class of organic dyes, have a strong tendency to self‐aggregate in water, thus greatly restricting their phototheranostic applications. Herein, we report a water‐soluble PDI cyclophane "Gemini Box" (GBox‐14+), consisting of a central PDI chromophore enclosed by double‐sided cationic molecular straps. Owing to the effective spatial isolation, the chromophore self‐aggregation can be completely eliminated, even in a concentrated aqueous solution up to 2 mM. To our knowledge, GBox‐14+ represents an interesting example of a fluorescent PDI cyclophane in water, capable of being employed for lysosome‐targetable live‐cell imaging. More importantly, the highly concentrated aqueous solution of PDI radical anion can be significantly stabilized by GBox‐14+ to exhibit an excellent near‐infrared photothermal effect, which was further exploited for efficient and selective antibacterial applications. This work provides a new access to water‐soluble non‐aggregated organic dyes and promotes their potential biomedical applications. [ABSTRACT FROM AUTHOR]

We herein describe a new design principle to achieve B/N‐doped cyclophane where an electron‐donor block of three triarylamines (Ar3N) and an acceptor block of three triarylboranes (Ar3B) are spatially separated on opposite sides of the π‐extended ring system. DFT computations revealed the distinct electronic structure of the block‐type macrocycle MC‐b‐B3N3 with a greatly enhanced dipole moment and reduced HOMO–LUMO energy gap in comparison to its analogue with alternating B and N sites, MC‐alt‐B3N3. The unique arrangement of borane acceptor Ar3B and amine donor Ar3N components in MC‐b‐B3N3 induces exceptionally strong intramolecular charge transfer in the excited state, which is reflected in a largely red‐shifted luminescence at 612 nm in solution. The respective linear open‐chain oligomer L‐b‐B3N3 was also synthesized for comparison. Our new approach to donor–acceptor macrocycles offers important fundamental insights and opens up a new avenue to unique optoelectronic materials. [ABSTRACT FROM AUTHOR]