The halogen bond is well known for its ability to assemble supramolecules. Here, using NMR experiments, the authors reveal the role of these bonds in dynamic processes, finding that the halogen bond directly catalyzes dynamical rotation in solid cocrystals by reducing the associated energy barrier.
Supramolecular chemistry specializes in non-covalent interactions. These weak and reversible forces—such as hydrogen bonds, hydrophobic forces, van der Waals forces, and metal–ligand coordination—are key to understanding biological processes and self-assembling systems, and to constructing complex materials and molecular machinery. In the several decades since its conception, supramolecular chemistry has become a truly interdisciplinary research area, providing insights into and spurring developments across biology, chemistry, nanotechnology, materials science, and physics.
In this collection, we highlight a selection of recent experimental and theoretical studies published in Nature Communications, which we hope reflect the true breadth of supramolecular chemistry as a discipline. The collection features advances in building discrete assemblies and extended material systems, all through the clever design of non-covalently organizing components. We also showcase fundamental research that furthers our understanding of the range of interactions that make up the supramolecular chemist’s toolbox.
Halogen bonding can be exploited for the design of functional supramolecular materials, but heavier elements that are known to accept a halogen bond remain limited. Here, the authors demonstrate the formation of two-component cocrystals based on halogen bonds with phosphorus, arsenic and antimony.
Homo radical spin-pairing interactions between two identical aromatic radicals are common in supramolecular chemistry, but hetero interactions between two different aromatic radicals are seldom observed. Here, the authors find that hetero radical pairing between a radical cation and a radical anion, together with Coulombic attraction, can drive host-guest recognition, representing a new supramolecular recognition motif.
Attractive, non-covalent interactions between aromatic rings—termed π−π stacking—is common in chemistry but difficult to model. Here the authors report a quantum-mechanical model to show the importance of collective charge fluctuations for understanding pi-stacked supramolecular systems.
Deuterating a hydrogen bond can change the bond’s geometry, a phenomenon known as the geometric isotope effect (GIE). Here, the authors find that a hydrogen-bonded host–guest crystal, imidazolium hydrogen terephthalate, exhibits significant GIE on its hydrogen bonds, changing its crystal phases and bulk dielectric properties.
Hydrogen-bonds are widely found in many systems, such as DNAs and supramolecular assemblies, but it remains challenging to detect their dynamics at a molecular level. Here, Zhou et al. study the stochastic arrangement of hydrogen bonds using single-molecule junctions connected to graphene electrodes.
Complex assembly pathways often involve transient, partly-formed intermediates that are challenging to characterize. Here, the authors present a simple and rapid spectroscopic thermal hysteresis method for mapping the energy landscapes of supramolecular assembly.
Bottom-up fabrication via on-surface molecular self-assembly is a useful way to make nanomaterials, but finding appropriate precursor molecules for a given structure remains a challenge. Here the authors present an informatics technique linking self-assembled structures with precursor properties, helping identify molecules for target nanomaterials.
Molecular self-assembly is controlled by chemical and entropic factors, but theory has not been able to differentiate the role of each. Here, the authors unambiguously address this question for self-assembly on metal surfaces, using a new computational method that bridges coarse-grained and atomistic approaches.
Dynamic diversity of synthetic supramolecular polymers in water as revealed by hydrogen/deuterium exchange
Understanding the dynamics of supramolecular architectures without using labels is crucial for developing advanced biosystems. Here, the authors show kinetic hydrogen/deuterium exchange profiles for a series of water-soluble supramolecular polymers.
Accessing the dynamics of soft self-assembled materials at high resolution is very difficult. Here the authors show atomistic and coarse-grained modelling combined with enhanced sampling to characterize the molecular mechanisms and kinetics of monomer exchange in synthetic supramolecular polymers.
The weak and directional CH-π hydrogen bond has rarely been exploited in the design of supramolecular complexes and molecular machinery. Here, the authors construct a bowl-in-tube complex stabilized solely by concyclic CH-π hydrogen bonds, and show that the guest exhibits single-axis rotational motion despite tight association with the host.
Though dynamics of molecules are generally restricted by intermolecular contacts, C60 fullerene is able to rotate freely despite being tightly bound inside a molecular host. Here, the authors study the solid-state dynamics of this host-guest system to understand the anomalous relationship between tight association and low friction.
A deeper understanding of the mechanics of molecular machines is limited by the fast motions which are in the nanosecond or picosecond timescale. Here the authors present a real-time observation of structural changes in a rotaxane-based molecular shuttle by transient two-dimensional infrared spectroscopy.
Metal–peptide rings form highly entangled topologically inequivalent frameworks with the same ring- and crossing-numbers
For interlocking ring structures, knot theory predicts that the number of topologically different links increases with ring and crossing number. Here, the authors use a peptide folding-and-assembly strategy to selectively realize two highly entangled catenanes with 4 rings and 12 crossings, representing two of the 100 predicted topologies with this complexity.
Coordination-driven self-assembly of a molecular figure-eight knot and other topologically complex architectures
Molecular knots and links continue to fascinate synthetic chemists. Here, the authors use stacking and hydrogen-bonding interactions between a set of similar building blocks to construct several complex molecular topologies, including a figure-eight knot and a trefoil knot.
Water-mediated deracemization of a bisporphyrin helicate assisted by diastereoselective encapsulation of chiral guests
Deracemization is a powerful method which allows transformation of racemic mixtures into excess enantiomer, but was applied only to small chiral molecular systems so far. Here the authors report deracemization of a kinetically stable bisporphyrin helicate upon encapsulation of chiral aromatic guests.
Photoresponsive molecular capsules that can be used in water are rare. Here, the authors construct polyaromatic nanocapsules via self-assembly from photoswitch-bearing amphiphilic molecules in water. Light induces a structural change in the amphiphiles, triggering the capsule to disassemble into monomers and release encapsulated guests.
The structures of fullerenes, or buckyballs, are often very difficult to resolve. Here, the authors describe a decapyrrylcorannulene host with ten flexible pyrryl groups that can efficiently co-crystallize with diverse fullerene derivatives in a ‘hand-ball-hand’ fashion, allowing crystallographic identification of commonly known types of fullerenes.
Container-molecules capable of recognizing charged species possess great potential as sensors, but are typically limited by their rigid frameworks. Here, Sun and co-workers design a family of adaptive metal-organic macrocycles that exhibit shape and size induced-fit transformations upon anion-binding.
Hierarchical non-intertwined ring-in-ring complexes are intriguing but challenging supramolecular targets. Here, the authors describe a box-in-box assembly based on radical-pairing interactions between two rigid diradical dicationic cyclophanes; the inner box can further accommodate guests to form Russian doll-like assemblies.
Coordination-driven supramolecular assembly provides the ability to build molecular architectures of impressive complexity. Here, the authors use a series of linear metal-organic ligands with specific sequences to construct multiple generations of precisely-controlled, 2D fractal polycyclic supramolecules.
Nested structures are common throughout nature and art, yet remain challenging synthetic targets in supramolecular chemistry. Here, the authors design multitopic terpyridine ligands that coordinate into nested concentric hexagons, and show that these discrete supramolecules display potent antimicrobial activity.
Molecular capsules typically bind only guests with volumes smaller than their cavities. Here, the authors find that a polyaromatic capsule accommodates linear amphiphilic oligomers in a length-dependent manner, whereas short chains are fully crammed into the cavity, long chains can be incorporated into the capsule in a threaded fashion.
Supramolecular containers are promising enzyme mimics, but they currently accommodate only a limited range of chemical transformations. Here, the authors describe coordination cages that catalyze two-component cascade reactions without relying on an external or encapsulated catalytic species.
Induced-fit expansion and contraction of a self-assembled nanocube finely responding to neutral and anionic guests
Induced-fit binding, common in biological systems, is still relatively rare in artificial hosts. Here, the authors assemble a molecular cube from six gear-shaped faces, whose interdigitated design allows the cube to expand and contract in response to the size, shape, and charge of a guest molecule.
Adapting the cavity of a coordination capsule generally involves the addition or removal of subcomponents. Here, the authors report two vanadium-organic coordination nanocapsules with the same number of components but variable cavity sizes—an expanded ball and contracted octahedron—whose solvent-controlled interconversion is attributed to the versatile coordination geometry of the vanadium centers.
Under confinement, molecular switches lose the conformational freedom often needed to isomerize. Here, the authors show that a flexible coordination cage can adapt its shape to guide the photoisomerization of encapsulated spiropyrans, rendering them reversibly photochromic even within the confines of the cavity.
The complex, multicomponent structures often found in nature are difficult to mimic synthetically. Here, the authors assemble a molecular analogue of a peanut through coordinative and π-stacking interactions, in which a polyaromatic double capsule ‘pod’ held together by metal ions encapsulates fullerene ‘beans’.
Anion-capped metallohost allows extremely slow guest uptake and on-demand acceleration of guest exchange
Host—guest assemblies can exploit stimuli-responsive guest binding and release for molecular recognition, but are typically governed by thermodynamics alone. Here, the authors design macrocycles with removable and exchangeable anion caps, allowing for the kinetic trapping and on-demand exchange of guest ions.
New approaches are required to access metal-organic assemblies with unusual structural properties. Here, the authors use an in situ redox reaction to obtain a mixed-valence, Mn(II)/Mn(III)-containing metal-organic nanocapsule with an odd number of metal ions.
Sequence-selective encapsulation and protection of long peptides by a self-assembled FeII8L6 cubic cage
One of the challenges of synthetic self-assembled capsules is achieving selective recognition of specific cargoes. Here, authors synthesize a self-assembled porphyrin cubic cage that is capable of sequestering imidazole and thiazole-containing small molecules and peptides, protecting them from proteolysis.
High-throughput discovery of organic cages and catenanes using computational screening fused with robotic synthesis
Supramolecular assemblies remain of great importance to a variety of fields, yet their targeted design and synthesis remains highly challenging. Here, Cooper and colleagues combine computational screening with high-throughput robotic synthesis and discover 33 new organic cage molecules that form cleanly in one-pot syntheses.
Molecules exhibiting Möbius topology are fascinating but challenging synthetic targets. Here, the authors report the elegant synthesis and crystal structure of a catenane formed from two fully conjugated, interlocked Möbius nanohoops, and use theoretical calculations to understand its conformational stability and aromaticity.
Unidirectional rotation in a synthetic molecular motor is typically driven by intrinsic asymmetry or sequences of chemical transformations. Here, the authors control the direction of a molecule’s rotation through supramolecular binding of a chiral guest and subsequent transfer of its chiral information.
Mechanically interlocked molecules are extensively applied as artificial molecular machines but rotaxane-branched dendrimers are rarely explored because of synthetic challenges. Here the authors present the construction of dual stimuli-responsive rotaxane-branched dendrimer which can be stimulated by DMSO or acetate ions.
Higher-generation type III-B rotaxane dendrimers with controlling particle size in three-dimensional molecular switching
The complexity of rotaxane dendrimers poses a great synthetic challenge and the synthesis of higher generation rotaxane dendrimers has therefore rarely been reported. Here the authors report the synthesis of acid-base switchable rotaxane dendrimers up to generation 4 and demonstrate the uptake and release of guest molecules.
Spiro compounds contain two or more rings linked together through one common atom. Here the authors provide a method to backfold both rings, producing spiro quasicatenanes, via a strategy of temporarily linking the linear intermediates with covalent bonds.
Rotaxanes are interlocked molecules that can undergo sliding and rotational movements and can be used in artificial molecular machines and motors. Here, Simmel and co-workers show a rigid rotaxane structures consisting of DNA origami subunits that can slide over several hundreds of nanometres.
Metal-centred azaphosphatriptycene gear with a photo- and thermally driven mechanical switching function based on coordination isomerism
In metal-based molecular motors, the motion is generally triggered by changes in the ligand coordination around the metal centre. Here, the authors synthesize a molecular gear that switches between states through photo- and thermally driven geometrical isomerization around a platinum ion.
Ultra-strong long-chain polyamide elastomers with programmable supramolecular interactions and oriented crystalline microstructures
Long-chain polyamides could bridge the gap between traditional polyamides and polyethylenes. Here the authors show the preparation of diamide diene monomers derived from natural resources coupled by thiol-ene addition copolymerization to form long-chain amide-containing polymers for the synthesis of ultra-strong elastomers.
Self-assembly of carbohydrates play an integral part in the design of higher ordered structures, but is limited to amphiphiles where the carbohydrate is covalently bound to a hydrophobic tail. Here the authors show that sugars direct the self-assembly of insoluble curcumin and the formation of well-defined capsules.
The supra-amphiphiles spontaneously assemble to well-defined nanostructures but control of shape and size of supramolecular nanostructures is still a great challenge. Here the authors demonstrate control over shape and size of self-assemblies by using the recognition motifs of an amphiphilic porphyrin
Two-dimensional tessellation by molecular tiles constructed from halogen–halogen and halogen–metal networks
Molecular tessellations of complex tilings are difficult to design and construct. Here, the authors show that molecular tessellations can be formed from a single building block that gives rise to two distinct supramolecular phases, whose self-similar subdomains serve as tiles in the periodic tessellations.
Modulating the structural and transient characteristics of synthetic nanostructures can be achieved by temporal control of supramolecular assemblies. Here the authors show a biomimetic, ATP-selective and fuel-driven controlled supramolecular polymerization of a phosphate receptor functionalised monomer.
Dynamically controlling the conformations of 1D elongated supramolecular polymers can induce functions comparable to protein folding/unfolding. Here the authors show light-induced conformational changes of azobenzene-based supramolecular polymers from helically coiled to extended/randomly coiled conformations.
Nature can precisely control monomer sequences in biopolymers, but this is somewhat problematic in the formation of synthetic polymers. Here the authors show sequence-controlled supramolecular terpolymerization via self-sorting behavior among three sets of monomers possessing mismatched host-guest pairs.
Porosity in metal–organic materials typically relies on highly ordered crystalline networks, which hinders material processing and morphological control. Here, the authors use metal–organic polyhedra as porous monomers in supramolecular polymerization to produce colloidal spheres and gels with intrinsic microporosity.
Macroscopic helical chirality and self-motion of hierarchical self-assemblies induced by enantiomeric small molecules
Chirality transfer by chemical self-assembly has been studied intensively for years but chirality transfers along the same path remains elusive. Here the authors use a multiscale chemo-mechanical model to elucidate the mechanism underlying the chirality transfer via self-assembly in hierarchical camphorsulfonic acid doped polyaniline.
Perylene bisimides (PBI) exhibit interesting photophysical and self-assembly properties but detailed understanding of the correlation between packing motif and spectroscopic properties is lacking. Here the authors report on self-assembling of PBIs in liquid crystalline phases to give aggregates with J- and H-type coupling contribution between the chromophores.
A possible route to producing processable soft materials is by assembling metal organic cubes into hydrogels. Here the authors show charge-assisted H-bond driven self-assembly of Ga3+-based anionic metal organic cubes and suitable molecular binders towards multi-functional hydrogels.
Reaction-diffusion controls the spatial formation of many natural structures but is rarely applied to organic materials. Here, the authors couple reaction-diffusion to the self-assembly of a supramolecular gelator, introducing a strategy to forming soft, free-standing objects with controlled shape and functionality.
Formation of non-spherical polymersomes driven by hydrophobic directional aromatic perylene interactions
Polymersomes have become a powerful tool in drug delivery and synthetic biology, but their use can be restricted by a lack of versatile methods for shape control. Here the authors demonstrate access to a range of non-spherical polymersome morphologies by exploiting hydrophobic directional aromatic perylene interactions within the membrane structure.
Uniform two-dimensional square assemblies from conjugated block copolymers driven by π–π interactions with controllable sizes
Crystallization-driven processes play a vital role in preparing 2D nanostructures which makes structures with high symmetry hard to access. Here the authors present a non-crystallization approach which is based on π–π interactions of a copolymer for the fabrication of 2D symmetric structures with good dimensional control.
Achieving precise control of host–guest interactions in artificial systems is difficult. Here the authors use the thermodynamics of a system in equilibrium to control stepwise release and capture of cyclodextrin (guest) using a coordination polymer as the host and temperature as the stimulus.
Designing and synthesizing protein mimetic molecules to form crystalline structures can be a challenge. Here the authors show lattice self-assembly of cyclodextrin complexes into a variety of capsid like structures, such as, lamellae, helical tubes and hollow rhombic dodecahedra.
Perylene diimide-bithiophene macrocycles are electroactive and shape-persistent hosts. Here, the authors describe their self-assembly into a cellular organic semiconducting film whose voids are electrically sensitive to different guests, and which can function as the active layer in a field-effect transistor device.
Ultra-large supramolecular coordination cages composed of endohedral Archimedean and Platonic bodies
Host–guest chemistry in hollow coordination cages can be exploited for a range of applications, but is often limited by inner cavity dimensions. Here, Schmitt and co-workers fabricate supramolecular keplerates that possess ultra-large cross-sectional diameters and are composed of multiple sub-cages.
Temporal control over self-assembly processes is a desirable trait for discovering adaptable and controllable materials. Here the authors show that a chemical fuel driven system can not only self-assemble in a controlled manner, but can also result in precise control over the assembly and disassembly kinetics.
Temperature-controlled repeatable scrambling and induced-sorting of building blocks between cubic assemblies
In this paper, the authors study the temperature-controlled dynamic behavior of a system of nanocubes self-assembled from two different building blocks. Non-intuitively, the disordered, equilibrium state (a mixture of heteroleptic cubes) and the ordered, out-of-equilibrium state (a mixture of homoleptic cubes) are cycled by heating and subsequent rapid cooling.
Molecular memory with downstream logic processing exemplified by switchable and self-indicating guest capture and release
While many processes in biological cells can be understood in terms of molecular logic gates that process information sequentially and combinationally, the design and construction of such devices in the laboratory are unknown. Here the authors achieve this by the reversibly-controlled capture and release of guest molecules from host containers.
Several cell functions are based on the fuel-driven assembly and disassembly of supramolecular polymers under non-equilibrium conditions. Here, the authors show controlled formation and breaking of a supramolecular polymer by enzymatic phosphorylation and dephosphorylation of a building block by continuously adding ATP fuel and removing waste products.
Selection and persistence of chemical non-equilibrium species is crucial for the emergence of life and the exact mechanisms remain elusive. Here the authors show that phase separation is an efficient way to control selection of chemical species when primitive carboxylic acids are brought out-of-equilibrium by high-energy condensing agents.
Unravelling the fundamental mechanisms of emergence of complex behaviour is key to understanding living systems. Here, the authors provide a simple experimental platform to investigate and control a rich set of complex phenomena, akin to those seen in living organisms, from a nonliving system of colloidal nanoparticles.
Hydrogen bonds are powerful supramolecular motifs, owing to their selective and dynamic nature. Here, the authors build orthogonal hydrogen-bonding sites into a single molecule, allowing it to form diverse hierarchical assemblies and exhibit self-sorting behaviour in response to certain stimuli.
Understanding self-replication and persistence in an out-of-equilibrium state is key to designing systems with new properties mimicking “living systems”. Here, the authors developed a synthetic small molecule system in which a transient surfactant replicator is responsible for both an autocatalytic aggregation pathway and a destructive pathway.
Coupling compartmentalisation and molecular replication is essential for the development of evolving chemical systems. Here the authors show an oil-in-water droplet containing a self-replicating amphiphilic imine that can undergo repeated droplet division.
Molecules that act as both autocatalysts and material precursors offer exciting prospects for self-synthesizing materials. Here, the authors design a triazole peptide that self-replicates and then self-assembles into nanostructures, coupling autocatalytic and assembly pathways to realize a reproducing supramolecular system.
Multistate molecular systems usually rely on external energy inputs to switch between states. Here, the authors show that a bispyridyl calixpyrrole system directed by only weak noncovalent interactions and metal coordination can access six discrete structural states, with directional and sequential control.
One of the most dramatic effects of supramolecular assembly is the generation of homochirality in near-racemic systems. Here the authors rationalize the chiral amplification mechanism with a combined scanning tunneling microscopy and modelling study of surface-grown enantiomerically unbalanced supramolecular bilayers.
Control over the emerging chirality in supramolecular gels and solutions by chiral microvortices in milliseconds
Symmetry breaking and chiral amplification are fundamental principles in chemistry and biology but the control of initial chiral bias remains a great challenge. Here the authors show that chiral microvortices can lead to a selection of initial chiral bias of supramolecular systems composed of achiral molecules.
Understanding why and how molecules transfer their chirality into helical superstructures, including crystals, remains a challenge. Here, the authors show that topological defects not only promote the growth, but also control the helical morphology of crystals formed by chiral rod-shaped particles.
The sergeants-and-soldiers effect, in which a few chiral units induce chirality in a large number of achiral molecules, is difficult to quantify at the molecular level. Here, the authors devise an elegant strategy—combining theory and a system of pure organic polyhedra with chiral and achiral vertices—to understand the mechanism of chiral amplification in discrete molecular assemblies.
Chiral transcription in self-assembled tetrahedral Eu4L6 chiral cages displaying sizable circularly polarized luminescence
Controlling the chirality of self-assembled polyhedra is a synthetic challenge. Here, the authors stereoselectively form emissive lanthanide tetrahedral cages from a series of chiral ligands, and use their circularly polarized luminescence to explore the effect of ligand point chirality on supramolecular architecture.