The construction of supramolecular systems

A range of surfactant-accelerated hydrogels based on terpyridine-based assembly via strong dipole-dipole interactions

A universal hydrogelation strategy employs surfactant-coassembled supramolecular terpyridine (DA-BET) aggregates. Dipole-dipole interactions between DA-BET's distinct binding sites and surfactant ions primarily drive hydrogel formation. This platform integrates hydrophobic organics with surfactants, establishing a novel supramolecular approach for advancing environmental remediation soft materials.

Dynamic Hydrogels with Tunable Mechanics for 3D Organoid Derivation

The mechanical properties of the hydrogel play a pivotal role in governing the formation and development of 3D organoids in vitro. However, commonly employed natural hydrogels, such as Matrigel and other extracellular matrix (ECM)-derived products, are characterized by ill-defined and complex compositions, resulting in non-tunable mechanical properties. This limitation poses challenges in controlling organoids' developmental trajectory and 3D morphology. Although numerous synthetic hydrogels with well-defined chemical structures have recently been adopted to study organoids by modulating stiffness, advanced research emphasizes the importance of dynamic mechanical cues, such as dynamic stiffness softening and dynamic viscoelasticity, for optimal organoid derivation. These cues are essential for mimicking the dynamic physiological states of organoids during their growth. Despite their potential, the concept of dynamic hydrogels is often used interchangeably, and a systematic review is lacking to clarify this ambiguity. Furthermore, the mechanisms through which dynamic mechanical cues regulate organoid formation have not been thoroughly reported. This review endeavors to summarize and categorize dynamic hydrogels and reveal the effects of dynamic mechanics on organoid derivation. Additionally, the prospects of dynamic hydrogels in organoid derivation are deliberated to promote a more rational design of synthetic hydrogels, guiding organoid derivation and propelling organoid technology in biomedicine.

Supramolecular Polymorphism of the Hydrogen-Bonded C3-Symmetrical Hexadehydrotribenzo[12]annulene Derivative

The C3-symmetric hexadehydrotribenzo[12]annulene ([12]DBA) derivative (1a) with three tetradecylamide (-NHCOC14H29) chains capable of hydrogen-bonding interaction formed either a two-dimensional lamellar (LM) or a one-dimensional (1D) nanofiber (NF) molecular assembly, depending on the association state of the amide hydrogen bonds in the solution phase. The intermolecular amide hydrogen-bonding modes in the LM and NF structures were different from each other. The NF structure was metastable, 2.2 kJ mol-1 less stable than that of the LM structure, and was obtained through organogel formation. In CHCl3, 1a exhibited a 1D association behavior following the isodesmic model (K = 2.18 × 103 M-1) due to intermolecular amide hydrogen bonds, whereas the presence of CH3CN inhibited this association state. The NF structure had larger amplitude dynamics about the polar amide group than that of the LM structure, undergoing a phase transition from the NF to the LM structure upon heating. The absorption spectra of NF and solid-state LM were different from each other, exhibiting different optical properties. The coexistence of intermolecular amide hydrogen bonds and van der Waals interactions among the C3-symmetric molecules resulted in polymorphic phenomena, where energetically similar molecular assemblies were expressed.

Mapping in situ the assembly and dynamics in aqueous supramolecular polymers

Supramolecular polymers, bonded through directional non-covalent interactions, closely mimic dynamic behaviors of biological nanofibers. However, the complexity of assembly pathways makes it highly challenging to unravel the nature of supramolecular dynamics in aqueous environments. Here we introduce a precise combinatorial titration methodology to probe in situ the assembly of peptide amphiphiles (PAs). This approach reveals a binary assembly mechanism governed by equilibrium between spheroidal micelles and β-sheet polymers. Weakening hydrogen bonding shifts the equilibrium towards micelles and decreases the internal structural order of filamentous polymers, promoting supramolecular dynamics. Extending this methodology to two-component copolymerization systems, we find a surprising tendency to form blocky nanostructures with reduced internal phase separation as the mismatch in peptide sequence decreases. Interestingly, while well-mixed copolymers acquire different dynamics, mismatched ones retain the characteristic supramolecular motion of their homopolymer counterparts. These critical insights into supramolecular dynamics offer strategies to tailor the dynamic functions of supramolecular nanomaterials.

Exo-templating via pseudorotaxane formation reduces pathway complexity in the multicomponent self-assembly of M12L24 nanospheres

Selective formation of multicomponent structures via the self-assembly of numerous building blocks is ubiquitous in biological systems but challenging to emulate synthetically. More components introduce additional possibilities for kinetic intermediates with trap-state ability, hampering access to desired products. In covalent chemistry, templates, reagents and catalysts are applied to create alternative pathways for desired product formation. Analogously, we enlist exo-templating to mould the formation of large, multicomponent supramolecular structures. Specifically, a charged ring docks at 1,5-dioxynaphthalene stations within exo-functionalized building blocks to promote formation of cuboctahedral Pd12L24 nanospheres via exoskeletal templating. With the exo-templating ring present, nanosphere formation occurs via small Pdx-Ly oligomers, while in the absence of the ring a Pdx-Ly polymer resting state rapidly evolves, from which nanosphere formation occurs slowly. We demonstrate a form of kinetic templating-via intermediate destabilization-resembling properties observed in catalysis. Importantly, unlike typically employed endo-templates, we demonstrate that exo-templating is particularly suited for larger, complex, self-assembled structures.

Redox-driven photoselective self-assembly

Self-assembly via non-covalent interactions is key to constructing complex architectures with advanced functionalities. A noncovalent synthetic chemistry approach, akin to organic chemistry, allows stepwise construction with enhanced control. Here, we explore this by coupling Pt(II) complex self-assembly with a redox reaction. Oxidation to Pt(IV) creates a non-emissive monomer that, upon reduction to Pt(II), forms luminescent gels with unique kinetic and thermodynamic pathways. UV irradiation induces Pt(IV) reduction, generating supramolecular fibers with Pt∙∙∙Pt interactions, enhancing photophysical properties and enabling visible light absorption up to 550 nm. This allows photoselective growth, where fibers convert surrounding Pt(IV) to Pt(II), promoting growth over nucleation, as observed via real-time fluorescence microscopy.

Elucidating the Boundary of Intercalation vs Sequestration in Supramolecular Polymers by Retrosynthetic Design Toward the Construction of Complex Supramolecular Systems

Controlled social self-sorting by intercalation can offer distinct properties at the supramolecular level that go beyond the sum of its parts. Likewise, controlling narcissistic self-sorting by sequestration can induce unique system properties. In contrast, the interface between the two cases has hitherto remained underexplored, and clear design rules remain elusive. Herein it is demonstrated that by fine-tuning the molecular similarity of supramolecular synthons, intricate control over concerted supramolecular equilibria can be achieved. By reducing the molecular similarity, a former intercalator can be tuned to become a strong or weak sequestrator. Understanding these roles in binary mixtures allows to rationalize more complex tertiary systems. Consequently, the influence of an uncommon dual sequestration mechanism is revealed. Further, an unprecedented hybrid mechanism between supramolecular intercalation and sequestration can be demonstrated. We are hopeful that the results presented herein will contribute to the development and understanding of concerted processes in complex supramolecular systems.

Cascade of phase transitions in a dipeptide supramolecular assembly triggered by a single fatty acid

Significant progress has been achieved with diversity of short peptide supramolecular assemblies. However, their programmable phase modulation by single stimulus remains a great challenge. Herein, we demonstrate a dipeptide supramolecular system undergoes sequentially coupled phase transitions upon hydrogen bonding association and dissociation triggered by a single fatty acid. To be specific, fatty acid at a low specific ratio mediates gel-crystal transformation of the dipeptide supramolecular assembly by rearrangement of hydrogen bonding interactions. Moreover, fatty acid at a high specific ratio induces crystal-sol transition by protonation of the dipeptide, generating strong electrostatic repulsion to cleave hydrogen bonding interactions. Remarkably, the cascade of phase transitions enables spontaneous solid-liquid separation of the dipeptide from one dispersion phase and further dissolution in another in a capture and release fashion. In contrast, it is not facilitated by individual phase transition. Our work creates competitive pathways to achieve integration of phase transitions in a simple dipeptide supramolecular system. It is useful to deeply understand the dynamic and complex biomolecular condensates in nature and with important implications for efficient collection of biomolecules.

Supramolecular Polymers for Drug Delivery

Supramolecular polymers are constructed through highly reversible and directionally specific non-covalent interactions between monomer units. This unique feature enables supramolecular polymers to undergo controlled structural reconfiguration and functional transformation in response to external stimuli, imparting them with high environmental responsiveness and self-healing properties. In particular, supramolecular polymers exhibit several specific advantages compared to conventional polymers, such as inherent degradability, the ease of preparation and the incorporation of functional units, and smart responsiveness to various biological stimuli. These characters make supramolecular polymers promising candidates for intelligent drug delivery systems in complex biological environments. In this review, we comprehensively summarize the latest developments and representative achievements of supramolecular polymers in drug delivery fields, focusing primarily on the design and synthesis, the properties and functionalities, and the practical applications of supramolecular polymers in small molecule drug delivery, gene therapy, and protein delivery. Finally, we highlight future research directions, focusing on multifunctionality, adaptability, and personalized therapy. We focus on recent studies that address key challenges in the field, providing rational polymer design, important properties, functionality, and understanding delivery strategies. These developments are expected to advance supramolecular polymers as new platforms of intelligent drug delivery systems, offering innovative solutions for the treatment of complex diseases.

First-in-human feasibility study of the aXess graft (aXess-FIH): 6-Month results

OBJECTIVE

The creation of an arteriovenous fistula (AVF) is considered the most effective hemodialysis (HD) vascular access. For patients who are not suitable for AVF, arteriovenous grafts (AVGs) are the best access option for chronic HD. However, conventional AVGs are prone to intimal hyperplasia, stenosis, thrombosis, and infection. Xeltis has developed an AVG as a potential alternative to currently available AVGs based on the concept of endogenous tissue restoration. The results of the first 6-month follow-up are presented here.

METHODS

The aXess first-in-human (FIH) study [NCT04898153] is a prospective, single-arm, multicenter feasibility study that evaluates the early safety and performance of the aXess Hemodialysis Graft. A total of 20 patients with end-stage renal disease were enrolled across six European investigational sites.

RESULTS

At 6-months follow-up, all grafts were patent with primary and secondary patency rates were 80% and 100%, respectively. Three patients required a re-intervention to maintain graft patency, while one re-intervention was required to restore patency. One graft thrombosis and zero infections were reported.

CONCLUSION

The expected advantages of the novel aXess Hemodialysis Graft over conventional AVGs would be evaluated by the analysis on long-term safety and effectiveness during the 5-year follow-up of the currently ongoing trial.

On the Stability of Metastable Monomers to Bias the Supramolecular Polymerization of Naphthalendiimides

Herein, we report the synthesis of the naphthalendiimides (NDIs) 1-3 endowed with peripheral 3,4,5-trialkoxybenzamide units and a variable number of 1,2,3-triazole rings. Both the benzamide units and the triazole rings are able to form six- or seven-membered intramolecularly H-bonded pseudocycles that behave as metastable monomeric units. Whilst freshly prepared solutions of 1-3 afford H-type aggregates, the presence or lack of the 1,2,3-triazole rings strongly conditions the kinetics and stability of the resulting aggregated species. These structural features result in highly stable metastable monomeric species M* for the symmetric 2 that can be trapped for long periods of time when the sample is subject to a heating/cooling cycle. Contrary to NDI 2, the M* species formed by 1 and 3 evolve to the final supramolecular polymers in shorter times. A detailed experimental and theoretical study display the different non-covalent supramolecular forces operating in the stabilization of such M* species. In all cases, but especially in those NDIs endowed with the triazoles rings (NDIs 2 and 3), a number of conformers for the metastable monomeric units can be modelled. The high stability of such monomeric species justifies the delay in the formation of the H-type aggregates.

Dynamic Peptide Nanoframework-Guided Protein Coassembly: Advancing Adhesion Performance with Hierarchical Structures

Hierarchical structures are essential in natural adhesion systems. Replicating these in synthetic adhesives is challenging due to intricate molecular mechanisms and multiscale processes. Here, we report three phosphorylated peptides featuring a hydrophobic self-assembly motif linked to a hydrophilic phosphorylated sequence (pSGSS), forming peptide fibril nanoframeworks. These nanoframeworks effectively coassemble with elastin-derived positively charged proteins (PCP), resulting in complex coacervate-based adhesives with hierarchical structures. Our method enables the controlled regulation of both cohesion and adhesion properties in the adhesives. Notably, the complex adhesives formed by the dityrosine-containing peptide and PCP demonstrate an exceptional interfacial adhesion strength of up to 30 MPa, outperforming most known supramolecular adhesives and rivaling cross-linked chemical adhesives. Additionally, these adhesives show promising biocompatibility and bioactivity, making them suitable for applications such as visceral hemostasis and tissue repair. Our findings highlight the utility of bioinspired hierarchical assembly combined with bioengineering techniques in advancing biomedical adhesives.

Kinetic Control over Social and Narcissistic Self-Sorting from Multicomponent Mixtures in Seed-Initiated Supramolecular Polymerization by Fine-Tuning of Steric Effects

Supramolecular polymers offer an intriguing possibility to transfer molecular properties from the nano- to the mesoscale. Towards this achievement, seed-initiated supramolecular polymerization has emerged as a powerful tool, as it prevents unlimited growth and enables size control of the assembly outcome. However, the potential application of the seeding method in the context of complex supramolecular systems is hitherto unclear. Herein we demonstrate that minute differences in molecular design in direct proximity to intermolecular recognition sites govern the molecular packing and in turn dictate the efficacy of seeded polymerization processes. We introduce a stepwise increase in steric demand in the central amino acid residue of a diamide system, which gradually increases the rotational displacement within the aggregated state. This fine-tuning of the molecular packing directly affects the propensity of the different aggregates to act as seeds for the other supramolecular synthons. In turn this allows us to selectively target specific trapped monomer states in binary mixtures for social or narcissistic seeded polymerization.

Synthetic chitin oligosaccharide nanocrystals and their higher-order assemblies

Self-assembly is a powerful strategy for creating complex architectures and elucidating the aggregation behaviors of biopolymers. Herein, we investigate the hierarchical assembly of chitin using a bottom-up approach based on synthetic oligosaccharides. We discovered that chitin oligosaccharides self-assemble into platelets, which then form higher-order structures. Subtle changes in experimental conditions drastically altered the self-assembly results, generating a wide array of higher-order architectures. Through systematic investigations employing transmission electron microscopy (TEM), photoinduced force microscopy (PiFM), and atomic force microscopy (AFM), we uncovered the role of water in shaping the different morphologies. This finding gave us the tools to promote the formation of chiral, uniform chitin oligosaccharide bundles. Our work not only sheds light on the fundamental aspects of chitin organization, but also suggests strategies for designing carbohydrate-based materials with tunable structures and properties.

Heterochiral π-Stacking Dimerization of Helical Secondary Structures with Emerging Supramolecular Chirality

A specific interface mode type was observed between helical secondary structures, in which a left-handed (M) helix binds specifically to a right-handed (P) helix along the helical axis, leading to the formation of discrete heterochiral helical dimers. Moreover, a concealed supramolecular chirality within the meso-supramolecular dimers was unexpectedly discovered by chiral induction, and was further underpinned by covalent meso-helix structures.

Bioinspired programmable coacervate droplets and self-assembled fibers through pH regulation of monomers

Phase separation and phase transitions pervade the biological domain, where proteins and RNA engage in liquid-liquid phase separation (LLPS), forming liquid-like membraneless organelles. The misregulation or dysfunction of these proteins culminates in the formation of solid aggregates via a liquid-to-solid transition, leading to pathogenic conditions. To decipher the underlying mechanisms, synthetic LLPS has been examined through complex coacervate formation from charged polymers. Nonetheless, temporal control over phase transitions from prebiotically relevant small organic synthons remains largely unexplored. Herein, we propose utilizing pH modulation to regulate the charge of small molecular building blocks, thereby controlling the LLPS process. Through a bio-inspired, enzyme-mediated pH-regulated reaction, we introduce temporal control over both LLPS and the transition from coacervates to supramolecular polymers. Additionally, by incorporating antagonistic pH modulators, we achieve transient LLPS and further temporal regulation of supramolecular polymer disassembly. Our investigation into pH-regulated LLPS provides a new avenue for exploring the stimuli-responsive, dynamic, and transient nature of LLPS.

Supramolecular Architectures of Dendritic Polymers Provide Irreversible Inhibitor to Block Viral Infection

In Nature, most known objects can perform their functions only when in supramolecular self-assembled from, e.g. protein complexes and cell membranes. Here, a dendritic polymer is presented that inhibits severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with an irreversible (virucidal) mechanism only when self-assembled into a Two-dimmensional supramolecular polymer (2D-SupraPol). Monomeric analogs of the dendritic polymer can only inhibit SARS-CoV-2 reversibly, thus allowing for the virus to regain infectivity after dilution. Upon assembly, 2D-SupraPol shows a remarkable half-inhibitory concentration (IC50 30 nM) in vitro and in vivo in a Syrian Hamster model has a good efficacy. Using cryo-TEM, it is shown that the 2D-SupraPol has a controllable lateral size that can be tuned by adjusting the pH and use small angle X-ray and neutron scattering to unveil the architecture of the supramolecular assembly. This functional 2D-SupraPol, and its supramolecular architecture are proposed, as a prophylaxis nasal spray to inhibit the virus interaction with the respiratory tract.

Abiotic Acyl Transfer Cascades Driven by Aminoacyl Phosphate Esters and Self-Assembly

Biochemical acyl transfer cascades, such as those initiated by the adenylation of carboxylic acids, are central to various biological processes, including protein synthesis and fatty acid metabolism. Designing cascade reactions in aqueous media remains challenging due to the need to control multiple, sequential reactions in a single pot and manage the stability of reactive intermediates. Herein, we developed abiotic cascades using aminoacyl phosphate esters, the synthetic counterparts of biological aminoacyl adenylates, to drive sequential chemical reactions and self-assembly in a single pot. We demonstrated that the structural elements of amino acid side chains (aromatic versus aliphatic) significantly influence the reactivity and half-lives of aminoacyl phosphate esters, ranging from hours to days. This behavior, in turn, affects the number of couplings we can achieve in the network and the self-assembly propensity of activated intermediate structures. The cascades are constructed using bifunctional peptide substrates featuring side chain nucleophiles. Specifically, aromatic amino acids facilitate the formation of transient thioesters, which preorganized into spherical aggregates and further couple into chimeric assemblies composed of esters and thioesters. In contrast, aliphatic amino acids, which lack the ability to form such structures, predominantly undergo hydrolysis, bypassing further transformations after thioester formation. Additionally, in mixtures containing multiple aminoacyl phosphate esters and peptide substrates, we achieved selective product formation by following a distinct pathway that favors subsequent reactions through reactivity changes and self-assembly. By coupling chemical reactions with molecules of varying reactivity time scales, we can drive multiple reaction clocks with distinct lifetimes and self-assembly dynamics, facilitating precise temporal and structural regulation.

Novel aerogels based on supramolecular G-quadruplex assembly with intrinsic flame retardancy and thermal insulation

The construction of supramolecular aerogels still faces great challenges. Herein, we present a novel bio-based supramolecular aerogel derived from G-Quadruplex self-assembly of guanosine (G), boric acid (B) and sodium alginate (SA) and the obtained GBS aerogels exhibit superior flame-retardant and thermal insulating properties. The entire process involves environmentally friendly aqueous solvents and freeze-drying. Benefiting from the supramolecular self-assembly and interpenetrating dual network structures, GBS aerogels exhibit unique structures and sufficient self-supporting capabilities. The resulting GBS aerogels exhibit overall low densities (36.5-52.4 mg/cm3), and high porosities (>95 %). Moreover, GBS aerogels also illustrate excellent flame retardant and thermal insulating properties. With an oxygen index of 47.0-51.1 %, it can easily achieve a V-0 rating and low heat, smoke release during combustion. This work demonstrates the preparation of intrinsic flame-retardant aerogels derived from supramolecular self-assembly and dual cross-linking strategies, and is expected to provide an idea for the realization and application of novel supramolecular aerogel materials.

Supramolecular materials constructed from synthetic glycopeptides via aqueous self-assembly and their bioapplications in immunotherapy

Synthetic glycopeptides capable of self-assembly in aqueous environments form a range of supramolecular nanostructures, such as nanoparticles and nanofibers, owing to their amphiphilic nature and the diverse structures of the saccharides introduced. These glycopeptide-based supramolecular materials are promising for immunotherapy applications because of their biocompatibility and multivalent saccharide display, which enhances lectin-saccharide interactions. This review highlights recent advances in the molecular design of synthetic glycopeptide-based supramolecular materials and their use as immunomodulatory agents.

Ag+-Induced Supramolecular Polymers of Folic Acid: Reinforced by External Kosmotropic Anions Exhibiting Salting Out

Introducing kosmotropic salts enhances protein stability and reduces solubility by withdrawing water from the protein surface, leading to 'salting out', a phenomenon we have mimicked in supramolecular polymers (SPs). Under the guidance of Ag+, folic acid (FA) self-assembled in water through slipped-stacking and hydrophobic interactions into elongated, robust one-dimensional SPs, resulting in thermo-stable supergels. The SPs exhibited temperature and dilution tolerance, attributed to the stability of the FA-Ag+ complex and its hydrophobic stacking. Importantly, FA-Ag+ SP's stability has been augmented by the kosmotropic anions, such as SO42-, strengthening hydrophobic interactions in the SP, evident from the enhanced J-band, causing improvement of gel's mechanical property. Interestingly, higher kosmotrope concentrations caused a significant decrease in SP's solubility, leading to precipitation of the reinforced SPs─a 'salting out' effect. Conversely, chaotropes like ClO4- slightly destabilized hydrophobic stacking and promoted an extended conformation of individual SP chain with enhanced solubility, resembling a 'salting in' effect.

Balancing volumetric and gravimetric capacity for hydrogen in supramolecular crystals

The storage of hydrogen is key to its applications. Developing adsorbent materials with high volumetric and gravimetric storage capacities, both of which are essential for the efficient use of hydrogen as a fuel, is challenging. Here we report a controlled catenation strategy in hydrogen-bonded organic frameworks (RP-H100 and RP-H101) that depends on multiple hydrogen bonds to guide catenation in a point-contact manner, resulting in high volumetric and gravimetric surface areas, robustness and ideal pore diameters (~1.2-1.9 nm) for hydrogen storage. This approach involves assembling nine imidazole-annulated triptycene hexaacids into a secondary hexagonal superstructure containing three open channels through which seven of the hexagons interpenetrate to form a seven-fold catenated superstructure. RP-H101 exhibits high deliverable volumetric (53.7 g l-1) and gravimetric (9.3 wt%) capacities for hydrogen under a combined temperature and pressure swing (77 K/100 bar → 160 K/5 bar). This work illustrates the virtues of supramolecular crystals as promising candidates for hydrogen storage.

Supramolecular assembly of dendronized diacetylenes into thermoresponsive chiral fibers and their covalent fixation through topochemical polymerization

By combination of dendritic topological structures with photopolymerizable diacetylene, here we report on supramolecular chiral assembly of the dendronized diacetylenes in water. These dendronized diacetylenes are constituted with three-fold dendritic oligoethylene glycols (OEGs), bridged with a dipeptide from phenylalanine and glycine. These dendronized amphiphiles exhibit intensive propensity to aggregate in water and form helical fibers, which show characteristic thermoresponsive behavior with phase transition temperatures dominated by hydrophilicity of the dendritic OEGs. Topochemical polymerization of these supramolecular fibers through UV irradiation transfers them into the covalent helical dendronized polydiacetylenes. Chirality of these dendronized polydiacetylenes can be mediated through the thermally-induced phase transitions, but is also intriguingly dependent on vortex via stirring. Through stirring the solutions, chiralities of the dendronized polydiacetylenes are inverted, which can be reversibly recovered after keeping still the solution. Hydrogels are formed from these dendronized diacetylenes through concentration-enhanced interactions between the supramolecular fibers. Their mechanical properties can be greatly increased through thermally-enhanced interactions between the fibers with storage moduli increased from 20 Pa to a few hundred Pa. In addition, through photo-polymerization, the supramolecular fibers are transferred into covalent dendronized polydiacetylenes, and the corresponding hydrogels show much improved mechanical properties with storage moduli about 10 kPa.

Heat-activated growth of metastable and length-defined DNA fibers expands traditional polymer assembly

Biopolymers such as nucleic acids and proteins exhibit dynamic backbone folding, wherein site-specific intramolecular interactions determine overall structure. Proteins then hierarchically assemble into supramolecular polymers such as microtubules, that are robust yet dynamic, constantly growing or shortening to adjust to cellular needs. The combination of dynamic, energy-driven folding and growth with structural stiffness and length control is difficult to achieve in synthetic polymer self-assembly. Here we show that highly charged, monodisperse DNA-oligomers assemble via seeded growth into length-controlled supramolecular fibers during heating; when the temperature is lowered, these metastable fibers slowly disassemble. Furthermore, the specific molecular structures of oligomers that promote fiber formation contradict the typical theory of block copolymer self-assembly. Efficient curling and packing of the oligomers - or 'curlamers' - determine morphology, rather than hydrophobic to hydrophilic ratio. Addition of a small molecule stabilises the DNA fibers, enabling temporal control of polymer lifetime and underscoring their potential use in nucleic-acid delivery, stimuli-responsive biomaterials, and soft robotics.

Controlled Supramolecular Polymerization via Bioinspired, Liquid-Liquid Phase Separation of Monomers

Dynamic supramolecular assemblies, driven by noncovalent interactions, pervade the biological realm. In the synthetic domain, their counterparts, supramolecular polymers, endowed with remarkable self-repair and adaptive traits, are often realized through bioinspired designs. Recently, controlled supramolecular polymerization strategies have emerged, drawing inspiration from protein self-assembly. A burgeoning area of research involves mimicking the liquid-liquid phase separation (LLPS) observed in proteins to create coacervate droplets and recognizing their significance in cellular organization and diverse functions. Herein, we introduce a novel perspective on synthetic coacervates, extending beyond their established role in synthetic biology as dynamic, membraneless phases to enable structural control in synthetic supramolecular polymers. Drawing parallels with the cooperative growth of amyloid fibrils through LLPS, we present metastable coacervate droplets as dormant monomer phases for controlled supramolecular polymerization. This is achieved via a π-conjugated monomer design that combines structural characteristics for both coacervation through its terminal ionic groups and one-dimensional growth via a π-conjugated core. This design leads to a unique temporal LLPS, resulting in a metastable coacervate phase, which subsequently undergoes one-dimensional growth via nucleation within the droplets. In-depth spectroscopic and microscopic characterization provides insights into the temporal evolution of disordered and ordered phases. Furthermore, to modulate the kinetics of liquid-to-solid transformation and to achieve precise control over the structural characteristics of the resulting supramolecular polymers, we invoke seeding in the droplets, showcasing living growth characteristics. Our work thus opens up new avenues in the exciting field of supramolecular polymerization, offering general design principles and controlled synthesis of precision self-assembled structures in confined environments.

Noncovalent Catalyst-cum-Inhibitor Directed Supramolecular Pathway Selection and Asymmetry Amplification by Aggregate Cross-Nucleation

The key to any controlled supramolecular polymerization (CSP) process lies in controlling the nucleation step, which is typically achieved by sequestering monomers in a kinetically trapped state. However, kinetic traps that are shallow cannot prevent spontaneous nucleation, thus limiting the applicability of the CSP in such systems. We use a molecular additive to overcome this limitation by modifying the energy landscape of a competitive self-assembly process and increasing the kinetic stability of an otherwise short-lived trap state. The additive achieves this by simultaneously catalyzing OFF-pathway nucleation and inhibiting ON-pathway aggregation. In the process, it guides the molecular assembly exclusively toward the OFF-pathway aggregate analogue. The mechanisms of OFF-pathway catalysis and ON-pathway inhibition are elucidated. By specifically targeting the nucleation step, it was possible to achieve pathway selection at an extremely low additive-to-monomer ratio of 1:100. The generality of our approach is also demonstrated for other related molecular systems. Finally, removing the additive triggers the cross-nucleation of the ON-pathway aggregate on the surface of a less stable, OFF-pathway aggregate analogue. The resultant supramolecular polymer not only exhibits a more uniform morphology but more importantly, a marked improvement in the structural order that leads to an amplification of chiral asymmetry and a high absorption dissymmetry factor (gAbs) of ∼0.05.

Pseudohalide Ions as Ligands to Tune Architecture and Luminescence of Polymetallic CU(I) Assemblies

The reaction of preassembled Cu(I) bimetallic units {Cu2(dppm)2} and {Cu2(dppa)2} (dppm: bis(diphenylphosphino)methane and dppa: bis(diphenylphosphino)amine) with pseudohalide linkers (azido, dicyanamide, and tricyanomethanide) allows for the quantitative and selective preparation of three discrete tetrametallic metallacycles of formula [Cu4(μ2-dppm)4(N3)2](PF6)2, [Cu4(μ2-dppm)4(N(CN)2)2](PF6)2, and [Cu4(μ2-dppm)4(C(CN)3)4]. To explore further the impact of the linker on the architecture and dimensionality of the molecular edifice, the study was extended to more sophisticated tetradentate cyanocarbanion ligands (tcnsMe-: 2-(methylthio)-1,1,3,3-propanetetracarbonitrile and tcnsEt-: 2-(ethylthio)-1,1,3,3-propanetetracarbonitrile). Three ladder-like one-dimensional coordination polymers and an octametallic metallacycle have been obtained. The careful comparison of the metric and geometrical intramolecular and intermolecular parameters observed in this series of seven derivatives allows for rationalization of their molecular architectures. The subtle balance between the length and steric hindrance of the ligand and the formation of noncovalent interaction networks greatly influences the topology and dimensionality of the resulting assemblies and will be discussed hereafter. The photophysical properties of these seven polymetallic Cu(I) compounds have also been also studied.

Triple Adaptation of Constitutional Dynamic Networks of Imines in Response to Micellar Agents: Internal Uptake-Interfacial Localization-Shape Transition

Understanding the behavior of complex chemical reaction networks and how environmental conditions can modulate their organization as well as the associated outcomes may take advantage of the design of related artificial systems. Microenvironments with defined boundaries are of particular interest for their unique properties and prebiotic significance. Dynamic covalent libraries (DCvLs) and their underlying constitutional dynamic networks (CDNs) have been shown to be appropriate for studying adaptation to several processes, including compartmentalization. However, microcompartments (e.g., micelles) provide specific environments for the selective protection from interfering reactions such as hydrolysis and an enhanced chemical promiscuity due to the interface, governing different processes of network modulation. Different interactions between the micelles and the library constituents lead to dynamic sensing, resulting in different expressions of the network through pattern generation. The constituents integrated into the micelles are protected from hydrolysis and hence preferentially expressed in the network composition at the cost of constitutionally linked members. In the present work, micellar integration was observed for two processes: internal uptake based on hydrophobic forces and interfacial localization relying on attractive electrostatic interactions. The latter drives a complex triple adaptation of the network with feedback on the shape of the self-assembled entity. Our results demonstrate how microcompartments can enforce the expression of constituents of CDNs by reducing the hydrolysis of uptaken members, unravelling processes that govern the response of reactions networks. Such studies open the way toward using DCvLs and CDNs to understand the emergence of complexity within reaction networks by their interactions with microenvironments.

What can molecular assembly learn from catalysed assembly in living organisms?

Molecular assembly is the process of organizing individual molecules into larger structures and complex systems. The self-assembly approach is predominantly utilized in creating artificial molecular assemblies, and was believed to be the primary mode of molecular assembly in living organisms as well. However, it has been shown that the assembly of many biological complexes is "catalysed" by other molecules, rather than relying solely on self-assembly. In this review, we summarize these catalysed-assembly (catassembly) phenomena in living organisms and systematically analyse their mechanisms. We then expand on these phenomena and discuss related concepts, including catalysed-disassembly and catalysed-reassembly. Catassembly proves to be an efficient and highly selective strategy for synergistically controlling and manipulating various noncovalent interactions, especially in hierarchical molecular assemblies. Overreliance on self-assembly may, to some extent, hinder the advancement of artificial molecular assembly with powerful features. Furthermore, inspired by the biological catassembly phenomena, we propose guidelines for designing artificial catassembly systems and developing characterization and theoretical methods, and review pioneering works along this new direction. Overall, this approach may broaden and deepen our understanding of molecular assembly, enabling the construction and control of intelligent assembly systems with advanced functionality.

Nonclassical Crystal Growth of Supramolecular Polymers in Aqueous Medium

A mechanistic understanding of the principles governing the hierarchical organization of supramolecular polymers offers a paradigm for tailoring synthetic molecular architectures at the nano to micrometric scales. Herein, the unconventional crystal growth mechanism of a supramolecular polymer of superbenzene(coronene)-diphenylalanine conjugate (Cr-FFOEt ) is demonstrated. 3D electron diffraction (3D ED), a technique underexplored in supramolecular chemistry, is effectively utilized to gain a molecular-level understanding of the gradual growth of the initially formed poorly crystalline hairy, fibril-like supramolecular polymers into the ribbon-like crystallites. The further evolution of these nanosized flat ribbons into microcrystals by oriented attachment and lateral fusion is probed by time-resolved microscopy and electron diffraction. The gradual morphological and structural changes reveal the nonclassical crystal growth pathway, where the balance of strong and weak intermolecular interactions led to a structure beyond the nanoscale. The role of distinct π-stacking and H-bonding interactions that drive the nonclassical crystallization process of Cr-FFOEt supramolecular polymers is analyzed in comparison to analogous molecules, Py-FFOEt and Cr-FF forming helical and twisted fibers, respectively. Furthermore, the Cr-FFOEt crystals formed through nonclassical crystallization are found to improve the functional properties.

Dynamic covalent synthesis

Dynamic covalent synthesis aims to precisely control the assembly of simple building blocks linked by reversible covalent bonds to generate a single, structurally complex, product. In recent years, considerable progress in the programmability of dynamic covalent systems has enabled easy access to a broad range of assemblies, including macrocycles, shape-persistent cages, unconventional foldamers and mechanically-interlocked species (catenanes, knots, etc.). The reversibility of the covalent linkages can be either switched off to yield stable, isolable products or activated by specific physico-chemical stimuli, allowing the assemblies to adapt and respond to environmental changes in a controlled manner. This activatable dynamic property makes dynamic covalent assemblies particularly attractive for the design of complex matter, smart chemical systems, out-of-equilibrium systems, and molecular devices.

Controlling Supramolecular Fiber Formation of Nucleopeptide by Guanosine Triphosphate

Cells use dynamic self-assembly to construct functional structures for maintaining cellular homeostasis. However, using a natural biological small molecule to mimic this phenomenon remains challenging. This work reports the dynamic microfiber formation of nucleopeptide driven by guanosine triphosphate, the small molecule that controls microtubule polymerization in living cells. Deactivation of GTP by enzyme dissociates the fibers, which could be reactivated by adding GTP. Molecular dynamic simulation unveils the mystery of microfiber formation of GBM-1 and GTP. Moreover, the microfiber formation can also be controlled by diffusion-driven GTP gradients across a semipermeable membrane in bulk conditions and the microfluidic method in the defined droplets. This study provides a new platform to construct dynamic self-assembly materials of molecular building blocks driven by GTP.

Spontaneous and Selective Peptide Elongation in Water Driven by Aminoacyl Phosphate Esters and Phase Changes

Nature chose phosphates to activate amino acids, where reactive intermediates and complex machinery drive the construction of polyamides. Outside of biology, the pathways and mechanisms that allow spontaneous and selective peptide elongation in aqueous abiotic systems remain unclear. Herein we work to uncover those pathways by following the systems chemistry of aminoacyl phosphate esters, synthetic counterparts of aminoacyl adenylates. The phosphate esters act as solubility tags, making hydrophobic amino acids and their oligomers soluble in water and enabling selective elongation and different pathways to emerge. Thus, oligomers up to dodecamers were synthesized in one flask and on the minute time scale, where consecutive additions activated autonomous phase changes. Depending on the pathway, the resulting phases initially carry nonpolar peptides and amphiphilic oligomers containing phosphate esters. During elongation and phosphate release, shorter oligomers dominate in solution, while the aggregated phase favors the presence of longer oligomers due to their self-assembly propensity. Furthermore we demonstrated that the solution phases can be isolated and act as a new environment for continuous elongation, by adding various phosphate esters. These findings suggest that the systems chemistry of aminoacyl phosphate esters can activate a selection mechanism for peptide bond formation by merging aqueous synthesis and self-assembly.

Artificial Molecular Ratchets: Tools Enabling Endergonic Processes

Non-equilibrium chemical systems underpin multiple domains of contemporary interest, including supramolecular chemistry, molecular machines, systems chemistry, prebiotic chemistry, and energy transduction. Experimental chemists are now pioneering the realization of artificial systems that can harvest energy away from equilibrium. In this tutorial Review, we provide an overview of artificial molecular ratchets: the chemical mechanisms enabling energy absorption from the environment. By focusing on the mechanism type-rather than the application domain or energy source-we offer a unifying picture of seemingly disparate phenomena, which we hope will foster progress in this fascinating domain of science.

Controlled Noncovalent Synthesis of Secondary Supramolecular Polymers

Dynamic supramolecular polymers, with their functional similarities to classical covalent polymers and their adaptive and self-repairing nature reminiscent of biological assemblies, have emerged as highly promising systems for the design of smart soft materials. Recent advancements in mechanistic investigations and novel synthetic strategies, such as living supramolecular polymerization, have significantly enhanced our ability to control the primary structure of these supramolecular polymers. However, realizing their full functional potential requires expanding their topological diversity in a manner akin to classical polymers as well as achieving precise molecular organization at higher hierarchical levels of self-assembly. In this paper, we present a remarkable advancement in this field, introducing an unprecedented and controlled synthesis of secondary supramolecular polymers. Our innovative strategy combines chirality-controlled surface-catalyzed secondary nucleation and a bioinspired peptide design, effectively stabilizing higher-order assembly. Furthermore, by harnessing this stereoselective nucleation process, we demonstrate the successful synthesis of racemic supramolecular polymers featuring parallelly stacked conglomerate microstructures─a previously unreported topology in synthetic self-assembled systems. Additionally, we elucidate that the extent of secondary supramolecular polymers can be regulated by modulating the enantiomeric excess of the chiral monomers. Consequently, our study unveils new topologies that exhibit enhanced higher-order structural complexity in the realm of supramolecular polymers.

Dual-Responsive Supramolecular Chiral Assemblies from Amphiphilic Dendronized Tetraphenylethylenes

Supramolecular assembly of amphiphilic molecules in aqueous solutions to form stimuli-responsive entities is attractive for developing intelligent supramolecular materials for bioapplications. Here we report on the supramolecular chiral assembly of amphiphilic dendronized tetraphenylethylenes (TPEs) in aqueous solutions. Hydrophobic TPE moieties were connected to the hydrophilic three-fold dendritic oligoethylene glycols (OEGs) through a tripeptide proline-hydroxyproline-glycol (POG) to afford the characteristic topological structural effects of dendritic OEGs and the peptide linker. Both ethoxyl- and methoxyl-terminated dendritic OEGs were used to modulate the overall hydrophilicity of the dendronized TPEs. Their supramolecular aggregates exhibited thermoresponsive behavior that originated from the dehydration and collapse of the dendritic OEGs, and their cloud point temperatures (Tcps) were tailored by solution pH conditions. Furthermore, aggregation-induced fluorescent emission (AIE) from TPE moieties was used as an indicator to follow the assembly, which was reversibly tuned by temperature variation at different pH conditions. Supramolecular assemblies from these dendronized amphiphiles exhibited enhanced supramolecular chirality, which was dominated mainly by the interaction balance between TPE with dendritic OEG and TPE with POG moieties and was modulated through different solvation by changing solution temperature or pH conditions. More interestingly, ethoxyl-terminated dendritic OEG provided a much stronger shielding effect than its methoxyl-terminated counterpart to prevent amino groups within the peptide from protonation, even in strong acidic conditions, resulting in different responsive behavior to the solution temperature and pH conditions for these supramolecular aggregates.

Multistep, site-selective noncovalent synthesis of two-dimensional block supramolecular polymers

Although the principles of noncovalent bonding are well understood and form the basis for the syntheses of many intricate supramolecular structures, supramolecular noncovalent synthesis cannot yet achieve the levels of precision and complexity that are attainable in organic and/or macromolecular covalent synthesis. Here we show the stepwise synthesis of block supramolecular polymers from metal-porphyrin derivatives (in which the metal centre is Zn, Cu or Ni) functionalized with fluorinated alkyl chains. These monomers first undergo a one-dimensional supramolecular polymerization and cyclization process to form a toroidal structure. Subsequently, successive secondary nucleation, elongation and cyclization steps result in two-dimensional assemblies with concentric toroidal morphologies. The site selectivity endowed by the fluorinated chains, reminiscent of regioselectivity in covalent synthesis, enables the precise control of the compositions and sequences of the supramolecular structures, as demonstrated by the synthesis of several triblock supramolecular terpolymers.

Crown ether-like discrete clusters for sodium binding and gas adsorption

Hexanuclear polyoxomolybdenum-based discrete supermolecules Na_x[Mo^V₆O₆(μ₂-O)₉(Htrz)_6-x(trz)_x]·nH₂O (x = 0, n = 15, 1; x = 1, n = 12, 2; x = 2, n = 10, 3; x = 2, n = 49, 4; Htrz = 1H-1,2,3-triazole) have been prepared and fully characterized with different amounts of sodium cations inside and outside the intrinsic holes. Structural analyses demonstrate that they all exist a triangular channel constructed by six molybdenum-oxygen groups with inner diameters of 2.86 (1), 2.48 (2), and 3.04 (3/4) Å, respectively. Zero, one, or two univalent enthetic guest Na⁺ have been hosted around the structural centers, which reflect the expansion and contraction effects at microscopic level. Water-soluble species can serve as crown ether-like metallacycles before and after the sodium binding. Diverse nanoscale pores are further formed through intermolecular accumulations with hydrogen bonding. Gas adsorption studies indicate that 2-4 can selectively adsorb CO₂ and O₂ but have little or even no affinities toward H₂, N₂, and CH₄. Theoretical calculations corroborate the roles of Na⁺ and auxiliary ligand with different states in bond distances, molecular orbitals, electrostatic potentials, and lattice energies in these discrete clusters. The binding orders of sodium cations in 2-4 are similar with the classical crown ethers, where 2 is the strongest one with 2.226(4)_av Å for sodium cation bonded to six O atoms.

Recent advances in supramolecular self-assembly derived materials for high-performance supercapacitors

The key preponderance of supramolecular self-assembly strategy is its ability to precisely assemble various functional units at the molecular level through non-covalent bonds to form multifunctional materials. Supramolecular materials have the merits of diverse functional groups, flexible structure, and unique self-healing properties, which make them of great value in the field of energy storage. This paper reviews the latest research progress of the supramolecular self-assembly strategy for the advanced electrode materials and electrolytes for supercapacitors, including supramolecular self-assembly for the preparation of high-performance carbon materials, metal-based materials and conductive polymer materials, and its beneficial effects on the performance of supercapacitors. The preparation of high performance supramolecular polymer electrolytes and their application in flexible wearable devices and high energy density supercapacitors are also discussed in detail. In addition, at the end of this paper, the challenges of the supramolecular self-assembly strategy are summarized and the development of supramolecular-derived materials for supercapacitors is prospected.

Tensor network construction for lattice gas models: Hard-core and triangular lattice models

The representation of complex lattice models in the form of a tensor network is a promising approach to the analysis of the thermodynamics of such systems. Once the tensor network is built, various methods can be used to calculate the partition function of the corresponding model. However, it is possible to build the initial tensor network in different ways for the same model. In this work, we have proposed two ways of constructing tensor networks and demonstrated that the construction process affects the accuracy of calculations. For demonstration purposes, we have done a brief study of the 4 nearest-neighbor (NN) and 5NN models, where adsorbed particles exclude all sites up to the fourth and fifth nearest neighbors from being occupied by another particle. In addition, we have studied a 4NN model with finite repulsions with a fifth neighbor. In a sense, this model is intermediate between 4NN and 5NN models, so algorithms designed for systems with hard-core interactions may experience difficulties. We have obtained adsorption isotherms, as well as graphs of entropy and heat capacity for all models. The critical values of the chemical potential were determined from the position of the heat capacity peaks. As a result, we were able to improve our previous estimate of the position of the phase transition points for the 4NN and 5NN models. And in the model with finite interactions, we found the presence of two first-order phase transitions and made an estimate of the critical values of the chemical potential for them.

Supramolecular Shish Kebabs: Higher Order Dimeric Structures from Ring-in-Rings Complexes with Conformational Adaptivity

Use of abiotic chemical systems for understanding higher order superstructures is challenging. Here we report a ring-in-ring(s) system comprising a hydrogen-bonded macrocycle and cyclobis(paraquat-o-phenylene) tetracation (o-Box) or cyclobis(paraquat-p-phenylene) tetracation (CBPQT⁴⁺ , p-Box) that assembles to construct discrete higher order structures with adaptive conformation. As indicated by mass spectrometry, computational modeling, NMR spectroscopy, and single-crystal X-ray diffraction analysis, this ring-in-ring(s) system features the box-directed aggregation of multiple macrocycles, leading to generation of several stable species such as H4G (1 a/o-Box) and H5G (1 a/o-Box). Remarkably, a dimeric shish-kebab-like ring-in-rings superstructure H7G2 (1 a/o-Box) or H8G2 (1 a/p-Box) is formed from the coaxial stacking of two ring-in-rings units. The formation of such unique dimeric superstructures is attributed to the large π-surface of this 2D planar macrocycle and the conformational variation of both host and guest.

Pathway Complexity in Supramolecular Copolymerization and Blocky Star Copolymers by a Hetero-Seeding Effect

This study unravels the intricate kinetic and thermodynamic pathways involved in the supramolecular copolymerization of the two chiral dipolar naphthalene monoimide (NMI) building blocks (O-NMI and S-NMI), differing merely by a single heteroatom (oxygen vs sulfur). O-NMI exhibits distinct supramolecular polymerization features as compared to S-NMI in terms of its pathway complexity, hierarchical organization, and chiroptical properties. Two distinct self-assembly pathways in O-NMI occur due to the interplay between the competing dipolar interactions among the NMI chromophores and amide-amide hydrogen (H)-bonding that engenders distinct nanotapes and helical fibers, from its antiparallel and parallel stacking modes, respectively. In contrast, the propensity of S-NMI to form only a stable spherical assembly is ascribed to its much stronger amide-amide H-bonding, which outperforms other competing interactions. Under the thermodynamic route, an equimolar mixture of the two monomers generates a temporally controlled chiral statistical supramolecular copolymer that autocatalytically evolves from an initially formed metastable spherical heterostructure. In contrast, the sequence-controlled addition of the two monomers leads to the kinetically driven hetero-seeded block copolymerization. The ability to trap O-NMI in a metastable state allows its secondary nucleation from the surface of the thermodynamically stable S-NMI spherical "seed", which leads to the core-multiarmed "star" copolymer with reversibly and temporally controllable length of the growing O-NMI "arms" from the S-NMI "core". Unlike the one-dimensional self-assembly of O-NMI and its random co-assembly with S-NMI, which are both chiral, unprecedentedly, the preferred helical bias of the nucleating O-NMI fibers is completely inhibited by the absence of stereoregularity of the S-NMI "seed" in the "star" topology.

Design of supramolecular hybrid nanomaterials comprising peptide-based supramolecular nanofibers and in situ generated DNA nanoflowers through rolling circle amplification

The artificial construction of multicomponent supramolecular materials comprising plural supramolecular architectures that are assembled orthogonally from their constituent molecules has attracted growing attention. Here, we describe the design and development of multicomponent supramolecular materials by combining peptide-based self-assembled fibrous nanostructures with globular DNA nanoflowers constructed by the rolling circle amplification reaction. The orthogonally constructed architectures were dissected by fluorescence imaging using the selective fluorescence staining procedures adapted to this study. The present, unique hybrid materials developed by taking advantage of each supramolecular architecture based on their peptide and DNA functions may offer distinct opportunities to explore their bioapplications as a soft matrix.

Metal-organic frameworks as chemical nanoreactors for the preparation of catalytically active metal compounds

Since the emergence of metal-organic frameworks (MOFs), a myriad of thrilling properties and applications, in a wide range of fields, have been reported for these materials, which mainly arise from their porous nature and rich host-guest chemistry. However, other important features of MOFs that offer great potential rewards have been only barely explored. For instance, despite the fact that MOFs are suitable candidates to be used as chemical nanoreactors for the preparation, stabilization and characterization of unique functional species, that would be hardly accessible outside the functional constrained space offered by MOF channels, only very few examples have been reported so far. In particular, we outline in this feature recent advances in the use of highly robust and crystalline oxamato- and oxamidato-based MOFs as reactors for the in situ preparation of well-defined catalytically active single atom catalysts (SACS), subnanometer metal nanoclusters (SNMCs) and supramolecular coordination complexes (SCCs). The robustness of selected MOFs permits the post-synthetic (PS) in situ preparation of the desired catalytically active metal species, which can be characterised by single-crystal X-ray diffraction (SC-XRD) taking advantage of its high crystallinity. The strategy highlighted here permits the always challenging large-scale preparation of stable and well-defined SACs, SNMCs and SCCs, exhibiting outstanding catalytic activities.

Introduction of Ferrocene as a Facilitator for the Construction of Supramolecular Polymers

Proper monomer design is the key to enhancing the strength of noncovalent interactions between the molecules toward the efficient formation of supramolecular polymers (SPs). We have designed and synthesized 1,n'-disubstituted ferrocene-azobenzene-long alkyl chains, Fc(CONH-Azo-TDP)₂ , to afford SPs with a high probability. The design exploits the ''molecular ball-bearing'' property of the ferrocene core, which allows two azobenzene arms to rotate in the planes of cyclopentadienyl rings, generating the most suitable molecular conformation required for SP formation. This ferrocene monomer formed a supergel consisting of SPs supported by strong intermolecular (H-bonding and π-π stacking) interactions and higher enthalpy gain than the reference molecules, where the central ferrocene core was replaced by flexible aliphatic as well as rigid benzene linkers. The molecular conformation involved in SPs, the strength of noncovalent interactions, and the process of supramolecular polymerization were investigated through NMR, UV-Vis, XRD and TEM studies. The results demonstrate that ferrocene may act as a good modulator for constructing efficient SPs.

How Subtle Changes Can Make a Difference: Reproducibility in Complex Supramolecular Systems

The desire to construct complex molecular systems is driven by the need for technological (r)evolution and our intrinsic curiosity to comprehend the origin of life. Supramolecular chemists tackle this challenge by combining covalent and noncovalent reactions leading to multicomponent systems with emerging complexity. However, this synthetic strategy often coincides with difficult preparation protocols and a narrow window of suitable conditions. Here, we report on unsuspected observations of our group that highlight the impact of subtle "irregularities" on supramolecular systems. Based on the effects of pathway complexity, minute amounts of water in organic solvents or small impurities in the supramolecular building block, we discuss potential pitfalls in the study of complex systems. This article is intended to draw attention to often overlooked details and to initiate an open discussion on the importance of reporting experimental details to increase reproducibility in supramolecular chemistry.