Perfluorinated Ligands Induce Meridional Metal Stereochemistry to Generate M8L12, M10L15, and M12L18 Prisms

Low-Symmetry Face-Capped Fe(II) Tetrahedra Through Anisotropic Ligand Extension

Low-symmetry cages are attractive metallo-supramolecular targets, as they may possess different characteristics to their higher symmetry analogs. There are no current generalizable routes for the formation of low-symmetry face-capped tetrahedra. We report here a strategy using tritopic tris-bidentate ligands with arms of different lengths to access novel tetrahedra. The use of "isosceles" ligands (two arms the same, one different) gives tetragonal disphenoid structures, while a "scalene" ligand (all three arms different) gives a rhombic disphenoid structure. In this last case, diastereoselectivity is also achieved. Distortion away from a perfect tetrahedron resulted in alteration of the character of the respective cage. More distorted cages were more prone to loss of structural integrity upon introduction of highly coordinating dimethyl sulfoxide solvent into the cage in acetonitrile solution. As well, increasing distortion was shown to increase the ease of oxidation from Fe(II) to Fe(III) within the cages.

Recent progress for chiral stationary phases based on chiral porous materials in high-performance liquid chromatography and gas chromatography separation

Chirality is a fundamental property of nature. Separation and analysis of racemates are of great importance in the fields of medicine and the production of chiral biopharmaceutical intermediates. Chiral chromatography has the characteristics of a wide separation range, fast separation speed, and high efficiency. The development and preparation of novel chiral stationary phases with good chiral recognition and separation capacity is the core and key of chiral chromatographic separation and analysis. In this work, the representative research progress of novel chiral porous crystal materials including chiral covalent organic frameworks, chiral porous organic cages, chiral metal-organic frameworks, and chiral metal-organic cages used as chiral stationary phases of capillary gas chromatography and high-performance liquid chromatography over the last 4 years is reviewed in detail. The chiral recognition and separation properties of the representative studies in this review are also introduced and discussed.

Anion-encapsulating, discrete prism and extended frusta, from trimetallated triangular macrocycles and linkers

Reaction of a trinuclear triangular macrocyclic complex Pb3L(CF3SO3)6 with bidentate linkers in a ratio of 3 equiv. of linker per 2 equiv. of complex, produces a prismatic structure with 4,4'-dipyridyl, and two unprecedented, extended 3D frustum-like structures with 1,2-di(4-pyridyl)ethylene and 1,4-di(4-pyridyl)benzene. The cavities of these structures encapsulate triflate anions.

Chirality-Driven Self-Assembly of Discrete, Homochiral FeII 2 L3 Cages

Coordination chemistry is a powerful method to synthesize supramolecular cages with distinct features that suit specific applications. This work demonstrates the synthesis of discrete, homochiral Fe^II ₂ L₃ cages via chirality-driven self-assembly. Specifically, the installation of chirality - at both the vertices and ligand backbones - allows the formation of discrete, homochiral Fe^II ₂ L₃ cages of different sizes via stereochemical control of the iron(II) centers. We observed that larger cages require multiple chiral centra (chiral ligands and vertices). In contrast, the formation of smaller cages is stereoselective with solely chiral ligands. The latter cages can also be formed from two chiral subcomponents, but only when they have matching chirality. Single-crystal X-ray diffraction of these smaller Fe^II ₂ L₃ cages revealed several non-covalent interactions as a driving force for narcissistic chiral self-sorting. This expected behavior was confirmed utilizing the shorter ligands in racemic form, yielding discrete, homochiral Fe^II ₂ L₃ cages formed in enantiomeric pairs.

Substituent-Induced Control of fac/mer Isomerism in Azine-NHC Fe(II) Complexes

The stereoselective synthesis of geometrical iron(II) complexes bearing azine-NHC ligands is described. Facial and meridional selectivity is achieved as a function of the steric demand of the azine unit, with no remarkable influence of the carbene nature. More specifically, meridional complexes are obtained upon selecting bulky 5-mesityl-substituted pyridyl coordinating units. Unexpectedly, increase of the steric hindrance in the α position with respect to the N coordinating atom results in an exclusive facial configuration, which is in stark contrast to the meridional selectivity induced by other reported α-substituted bidentate ligands. Investigation of the structure and the optical and electrochemical properties of the here-described complexes has revealed the non-negligible effect of the fac/mer ligand configuration around the metal center.

Beyond Platonic: How to Build Metal-Organic Polyhedra Capable of Binding Low-Symmetry, Information-Rich Molecular Cargoes

The field of metallosupramolecular chemistry has advanced rapidly in recent years. Much work in this area has focused on the formation of hollow self-assembled metal-organic architectures and exploration of the applications of their confined nanospaces. These discrete, soluble structures incorporate metal ions as 'glue' to link organic ligands together into polyhedra.Most of the architectures employed thus far have been highly symmetrical, as these have been the easiest to prepare. Such high-symmetry structures contain pseudospherical cavities, and so typically bind roughly spherical guests. Biomolecules and high-value synthetic compounds are rarely isotropic, highly-symmetrical species. To bind, sense, separate, and transform such substrates, new, lower-symmetry, metal-organic cages are needed. Herein we summarize recent approaches, which taken together form the first draft of a handbook for the design of higher-complexity, lower-symmetry, self-assembled metal-organic architectures.

Tailored metal–organic tetrahedral nanocages with aggregation-induced emission for an anti-counterfeiting ink and stimulus-responsive luminescence

Tailored metal–organic tetrahedral nanocages with aggregation-induced emission for an anti-counterfeiting ink and stimulus-responsive luminescence.

Supramolecular catalysis: the role of H-bonding interactions in substrate orientation and activation

Hydrogen bonding plays significant roles in various biological processes during substrate orientation and binding and therefore assists in assorted organic transformations. However, replicating the intricate selection of hydrogen bonds, as observed in nature, in synthetic complexes has met with only limited success. Despite this fact, recent times have seen the emergence of several notable examples where hydrogen bonds have been introduced in synthetic complexes. A few such examples have also illustrated the substantial role played by the hydrogen bonds in influencing and often controlling the catalytic outcome. This perspective presents selected examples illustrating the significance of hydrogen bonds offered by the coordination and the organometallic complexes that aid in providing the desired orientation to a substrate adjacent to a catalytic metal center and remarkably assisting in the catalysis.

Self-Assembly of a Purely Covalent Cage with Homochirality by Imine Formation in Water

Self-assembly of host molecules in aqueous media via metal-ligand coordination is well developed. However, the preparation of purely covalent counterparts in water has remained a formidable task. An anionic tetrahedron cage was successfully self-assembled in a [4+4] manner by condensing a trisamine and a trisformyl in water. Even although each individual imine bond is rather labile and apt to hydrolyze in water, the tetrahedron is remarkably stable or inert due to multivalence. The tetrahedral cages, as well as its neutral counterparts dissolved in organic solvent, have homochirality, namely that their four propeller-shaped trisformyl residues adopt the same rotational conformation. The cage is able to take advantage of hydrophobic effect to accommodate a variety of guest molecules in water. When a chiral guest was recognized, the formation of one enantiomer of the cage became more favored relative to the other. As a consequence, the cage could be produced in an enantioselective manner. The tetrahedron is able to maintain its chirality after removal of the chiral guest-probably on account of the cooperative occurrence of intramolecular forces that restrict the intramolecular flipping of phenyl units in the cage framework.

Solvent-dependent fac/mer-isomerization and self-assembly of triply helical complexes bearing a pivot part

Tris-chelate metal complexes of unsymmetrical bidentate ligands can form two geometric stereoisomers, facial (fac) and meridional (mer) isomers. Due to the small difference in their properties, the highly-selective synthesis of one of the isomers is challenging. We now designed a series of tripodal ligands with a tris(3-(2-(methyleneoxy)ethoxy)phenyl)methane pivot. Surprisingly, the ratio of the fac/mer isomers of the triply helical Fe^II complexes significantly changed depending on the solvents. To the best of our knowledge, this is the first example of fac/mer isomerism of a labile tris(2,2'-bipyridine) Fe^II complex governed by the solvent. Furthermore, well-defined self-assemblies were quantitatively produced by imine bond formation with a suitable diamine. The supramolecular assemblies contained only the fac isomer even though a mixture of the two isomers existed in solution before the condensation reaction. Namely, the self-assembly formation effectively adjusted the geometries of the building unit that results in the suitable supramolecular structure.

Exclusive formation of a meridional complex of a tripodand and perfect suppression of guest recognition

Tripodal ligands have been utilized for complexation-induced structural change, but all the tripodal complexes reported so far are facial isomers, which do not completely reduce the recognition ability by closing the binding pocket. We now report the first example of the selective synthesis of a meridional tripodal complex. The tripodal ligand with a 1,3,5-triethyl-2,4,6-tris(methylene)benzene pivot possessing 2,2'-bipyridine on each arm exclusively formed a mononuclear complex with the mer-[Fe(bpy)]2+ unit. The meridional tripodal complex has a unique structure in which one bipyridine unit is self-penetrated. As a result of cavity blockage, the ion recognition property of the tripodand has been successfully suppressed.

Self-assembly of a Mixed Valence Copper Triangular Prism and Transformation to Cage Triggered by an External Stimulus

A triangular prismatic metal-organic cage based on mixed valence copper ions has been designed and synthesized by using metallocycle panels and pillar ligands. The triangular prism will be quickly transformed to a 10-nuclear cage upon an external chemical stimulus, which features a bicapped square antiprism structure. This prismatic cage can act as a catalyst for oxidation of aromatic alcohols to their corresponding aromatic aldehydes with high yields at room temperature under O₂ atmosphere.

Oxidation triggers guest dissociation during reorganization of an FeII 4L6 twisted parallelogram

A three-dimensional FeII 4L6 parallelogram was prepared from ferrocene-containing ditopic ligands. The steric preference of the bulky ferrocene cores towards meridional vertex coordination brought about this new structure type, in which the ferrocene units adopt three distinct conformations. The structure possesses two distinct, bowl-like cavities that host anionic guests. Oxidation of the ferrocene FeII to ferrocenium FeIII causes rotation of the ferrocene hinges, converting the structure to an FeII 1L1 + species with release of anionic guests, even though the average charge per iron increases in a way that would ordinarily increase guest binding strength. The degrees of freedom exhibited by these new structures - derived from the different configurations of the three ligands surrounding a meridional FeII center and the rotation of ferrocene cores - thus underpin their ability to reconfigure and eject guests upon oxidation.

Metal-Organic Frameworks and Metal-Organic Cages - A Perspective

The fields of metal-organic cages (MOCs) and metal-organic frameworks (MOFs) are both highly topical and continue to develop at a rapid pace. Despite clear synergies between the two fields, overlap is rarely observed. This article discusses the peculiarities and similarities of MOCs and MOFs in terms of synthetic strategies and approaches to system characterisation. The stability of both classes of material is compared, particularly in relation to their applications in guest storage and catalysis. Lastly, suggestions are made for opportunities for each field to learn and develop in partnership with the other.

Balancing Ligand Flexibility versus Rigidity for the Stepwise Self-Assembly of M12 L24 via M6 L12 Metal-Organic Cages

Non-covalent interactions are important for directing protein folding across multiple intermediates and can even provide access to multiple stable structures with different properties and functions. Herein, we describe an approach for mimicking this behavior in the self-assembly of metal-organic cages. Two ligands, the bend angles of which are controlled by non-covalent interactions and one ligand lacking the above-mentioned interactions, were synthesized and used for self-assembly with Pd²⁺ . As these weak interactions are easily broken, the bend angles have a controlled flexibility giving access to M₂ (L1)₄ , M₆ (L2)₁₂ , and M₁₂ (L2)₂₄ cages. By controlling the self-assembly conditions this process can be directed in a stepwise fashion. Additionally, the multiple endohedral hydrogen-bonding sites on the ligand were found to play a role in the binding and discrimination of neutral guests.

Guest Binding Drives Host Redistribution in Libraries of CoII 4 L4 Cages

Two CoII 4 L4 tetrahedral cages prepared from similar building blocks showed contrasting host-guest properties. One cage did not bind guests, whereas the second encapsulated a series of anions, due to electronic and geometric effects. When the building blocks of both cages were present during self-assembly, a library of five CoII LA x LB 4-x cages was formed in a statistical ratio in the absence of guests. Upon incorporation of anions able to interact preferentially with some library members, the products obtained were redistributed in favor of the best anion binders. To quantify the magnitudes of these templation effects, ESI-MS was used to gauge the effect of each template upon library redistribution.

No, Not That Way, the Other Way: Creating Active Sites in Self-Assembled Host Molecules

This Account describes our efforts over the last decade to synthesize self-assembled metal–ligand cage complexes that display reactive functional groups on their interiors. This journey has taken us down a variety of research avenues, including studying the mechanism of reversible self-assembly, analyzing ligand self-sorting properties, post-assembly reactivity, molecular recognition, and binding studies, and finally reactivity and catalysis. Each of these individual topics are discussed here, as are the lessons learned along the way and the future research outlook. These self-assembled hosts are the closest mimics of enzymes to date, as they are capable of size- and shape-selective molecular recognition, substrate activation and turnover, as well as showing less common ‘biomimetic’ properties such as the ability to employ cofactors in reactivity, and alter the prevailing mechanism of the catalyzed reactions.

1 Introduction

2 Paddlewheels and Self-Sorting Behavior

3 First-Row Transition-Metal-Mediated Assembly: Sorting and Stereochemical Control

4 Post-Assembly Reactivity

5 Molecular Recognition and Catalysis

6 Conclusions and Outlook

Pyrroloindole-Based Dynamic Combinatorial Chemistry

We report a new class of building blocks for Dynamic Combinatorial Chemistry (DCC) based on the pyrroloindole scaffold. The attachment of l-cysteine on the α, α′ positions of the core makes the molecule suitable for disulfide exchange in aqueous dynamic combinatorial libraries (DCLs). The synthesis of the core follows a modified version of the Knoevenagel–Hemetsberger approach. The new building block (l-PI) is fluorescent (Φ = 48%) and relatively stable towards thermal and photodegradation. The chirality of the cysteine is transferred to the electron-rich pyrroloindole core. Homo- and heterochiral DCLs of l-PI with electron-deficient l- and d-naphthalenediimide (NDI) lead to similar library distributions regardless of the enantiomer used. When no salt is present, the major component is a dimer, while dimers and tetramers are obtained at increased ionic strength.

Assembling Pentatopic Terpyridine Ligands with Three Types of Coordination Moieties into a Giant Supramolecular Hexagonal Prism: Synthesis, Self-Assembly, Characterization, and Antimicrobial Study

Three dimensional (3D) supramolecules with giant cavities are attractive due to their wide range of applications. Herein, we used pentatopic terpyridine ligands with three types of coordination moieties to assemble two giant supramolecular hexagonal prisms with a molecular weight up to 42 608 and 43 569 Da, respectively. Within the prisms, two double-rimmed Kandinsky Circles serve as the base surfaces as well as the templates for assisting the self-sorting during the self-assembly. Additionally, hierarchical self-assembly of these supramolecular prisms into tubular-like nanostructures was fully studied by scanning tunneling microscopy (STM) and small-angle X-ray scattering (SAXS). Finally, these supramolecular prisms show good antimicrobial activities against Gram-positive pathogen methicillin-resistant Staphylococcus aureus (MRSA) and Bacillus subtilis (B. subtilis).

Solvent-assisted coordination driven assembly of a supramolecular architecture featuring two types of connectivity from discrete nanocages

A 3D nanocage architecture with two types of connectivity was successfully assembled from discrete supramolecular nanocages.

The rapid development of supramolecular chemistry provides a powerful bottom-up approach to construct various well-defined nano-architectures with increasing complexity and functionality. Compared to that of small and simple nanometric objects, the self-assembly of larger and more complex nanometric objects, such as nanocages, remains a significant challenge. Herein, we used a discrete nanocage as the monomer to successfully construct a novel three-dimensional (3D) supramolecular architecture, which comprises two types of nanocage building units with different connectivity, using the solvent-assisted coordination-driven assembly approach. The mechanism of this supramolecular assembly process was investigated by electrospray ionization mass spectrometry (ESI-MS) studies, which identified for the first time the formation of a nanocage dimer intermediate during the assembly process. The assembly of discrete nanocages into a 3D supramolecular architecture led to remarkable enhancement of stability and gas adsorption properties.

Waterproof architectures through subcomponent self-assembly

Construction of metal–organic containers that are soluble and stable in water can be challenging – we present diverse strategies that allow the synthesis of kinetically robust water-soluble architectures via subcomponent self-assembly.

Metal–organic containers are readily prepared through self-assembly, but achieving solubility and stability in water remains challenging due to ligand insolubility and the reversible nature of the self-assembly process. Here we have developed conditions for preparing a broad range of architectures that are both soluble and kinetically stable in water through metal(ii)-templated (M^II = Co^II, Ni^II, Zn^II, Cd^II) subcomponent self-assembly. Although these structures are composed of hydrophobic and poorly-soluble subcomponents, sulfate counterions render them water-soluble, and they remain intact indefinitely in aqueous solution. Two strategies are presented. Firstly, stability increased with metal–ligand bond strength, maximising when Ni^II was used as a template. Architectures that disassembled when Co^II, Zn^II and Cd^II templates were employed could be directly prepared from NiSO₄ in water. Secondly, a higher density of connections between metals and ligands within a structure, considering both ligand topicity and degree of metal chelation, led to increased stability. When tritopic amines were used to build highly chelating ligands around Zn^II and Cd^II templates, cryptate-like water-soluble structures were formed using these labile ions. Our synthetic platform provides a unified understanding of the elements of aqueous stability, allowing predictions of the stability of metal–organic cages that have not yet been prepared.

Supramolecular Polymer Cross-Linked by Discrete Tris-[2]pseudorotaxane Metallacycles and Its Redox-Responsive Behavior

A new discrete hexagonal metallacycle M containing tris-[2]pseudorotaxane moiety has been successfully designed and synthesized via coordination-driven self-assembly. The newly designed tris-[2]pseudorotaxane metallacycle was well characterized with nuclear magnetic resonance and mass spectra analysis. Such tris-[2]pseudorotaxane metallacycle M and pillar[5]arene dimer (PD) could further form a new family of cross-linked redox-responsive supramolecular polymer M⊃(PD)₃ through a host-guest interaction. Interestingly, the polymer M⊃(PD)₃ displayed redox-responsive behavior and showed tuned weight-average diffusion coefficients D upon redox stimuli, which is attributed to the changed coordination geometries of [Cu(phen)₂]⁺ and [Cu(phen)₂]²⁺ in such system.

Synthesis and Characterization of Self-Assembled Chiral FeII 2 L3 Cages

We present here the synthesis of chiral BINOL-derived (BINOL=1,1'-bi-2-naphthol) bisamine and bispyridine-aldehyde building blocks that can be used for the self-assembly of novel chiral FeII 2 L3 cages when mixed with an iron(II) precursor. The properties of a series of chiral cages were studied by NMR and circular dichroism (CD) spectroscopy, cold-spray ionization MS, and molecular modeling. Upon formation of the M2 L3 cages, the iron corners can adopt various isomeric forms: mer, fac-Δ, or fac-Λ. We found that the coordination geometry around the metal centers in R-Cages 1 and 2 were influenced by the chiral BINOL backbone only to a limited extent, as a mixture of cages was formed with fac and mer configurations at the iron corners. However, single cage species (fac-RR-Cage and fac-RS-Cage) that are enantiopure and highly symmetric were obtained by generating these chiral M2 L3 cages by using the bispyridine-aldehyde building blocks in combination with chiral amine moieties to form pyridylimine ligands for coordination to iron. Next to consistent NMR spectra, the CD spectra confirm the configurations fac-(Λ,Λ) and fac-(Δ,Δ) corresponding to RR- and RS-Cage, respectively.

Highlights from the 53rd EUCHEM conference on stereochemistry, Bürgenstock, Switzerland, May 2018

When we first heard of the Bürgenstock conference it was described as a guarded meeting in a remote location, undisturbed by modern diversions, with mysterious customs and a secret handshake. All of these rumors turned out to be completely true. We arrived at an undisclosed location and three young men, who knew our names upon sight, greeted us and gave us an agenda in which we discovered the identity of the speakers, moderators and other participants. We then had a few moments to bask in their glory before being treated to a delicious dose of chemistry. During the banquet, before the first lecture, this year's president, Prof. Ilan Marek, gave the opening address from a balcony reserved only for these meetings, rumors hold that it stands vacant all year in anticipation. He mentioned several of the traditions of the meeting, which we are not allowed to share of course, and described the joy of putting together this year's exciting program with the help of an exceptional organizing committee that included Prof. Cristina Nevado, Prof. Christian Bochet, Dr Fabrice Gallou and Dr Alain De Mesmaeker. He also introduced this year's guest of honor, Prof. Yitzhak Apeloig, and wished the best luck to the current Vice President and future President, Prof. Véronique Gouverneur, not only for preparing the 54th Bürgenstock Conference, but also with her duty this year, maintaining the good weather for the whole week. Although the official title of the conference is the EUCHEM conference on stereochemistry, the topics covered span a broad range of cutting edge chemical transformations and insights, which can appeal to anyone working in chemistry and its interfaces with other disciplines. We will briefly describe each of the talks following one of our favorite citable quotes from these inspiring speakers.

Luminescent Tetrahedral Molecular Cages Containing Ruthenium(II) Chromophores

We have designed linear metalloligands which contain a central photoactive [Ru(N^∧N)₃]²⁺ unit bordered by peripheral metal binding sites. The combination of these metalloligands with Zn(II) and Fe(II) ions leads to heterometallic tetrahedral cages, which were studied by NMR spectroscopy, mass spectrometry, and photophysical methods. Like the parent metalloligands, the cages remain emissive in solution. This approach allows direct incorporation of the favorable properties of ruthenium(II) polypyridyl complexes into larger self-assembled structures.

The crystal structure of [Fe2(PIMIC6)(AnthCO2)(CH3CN)]·[Fe2(PIMIC6)(AnthCO2)(CH3CN)0.9(CH2Cl2)0.1]·[Fe2(PIMIC6)(AnthCO2)(OH2)]·0.75CH3CN: a crystallographer's nightmare or a fascinating case of disorder?

Refinement of large crystal structures as well as that of disordered structures can be challenging. If both features come together, structure refinement has the potential of becoming a crystallographer's nightmare. Here, the refinement of the large and highly disordered structure of [Fe₂(PIMIC6)(AnthCO₂)(CH₃CN)]·[Fe₂(PIMIC6)(AnthCO₂)(CH₃CN)_0.9(CH₂Cl₂)_0.1]·[Fe₂(PIMIC6)(AnthCO₂)(OH₂)]·0.75CH₃CN [(1), PIMIC6 is a phenol-imine-based macrocycle, AnthCO₂ is an anthracene acid anion] is described and discussed. A total of 5311 parameters had to be refined to generate a model that allows for 14 400 possible arrangements of (1) in the asymmetric unit, making this structure one of the most complex structures in the Cambridge Structural Database to date. All disorders are exceptionally well resolved and exhaustive parameterizing affords a refinement model that is unique with respect to the detail of disorder refinement.

Interconversion of molecular face-rotating polyhedra through turning inside out

We report the post-synthesis interconversion of two enantiomeric organic cages through turning inside out. By scrutinizing the thermodynamics and kinetics, we are able to control the racemization rate by various reaction conditions and reveal that the turning-inside-out interconversion is realized through a partial disassembly pathway. The kinetics investigation also provides insight into the dynamic essence of imine chemistry using different solvents and catalysts.

Multiple Pathways in the Self-Assembly Process of a Pd4L8 Coordination Tetrahedron

The self-assembly of a Pd₄1₈ coordination tetrahedron (Tet) from a ditopic ligand, 1, and palladium(II) ions, [PdPy*₄]²⁺ (Py* = 3-chloropyridine), was investigated by a ¹H NMR-based quantitative approach (quantitative analysis of self-assembly process, QASAP), which allows one to monitor the average composition of the intermediates not observed by NMR spectroscopy. The self-assembly of Tet takes place mainly through three pathways and about half of the Tet structures were produced through the reaction of a kinetically produced Pd₃L₆ double-walled triangle (DWT) and 200-nm-sized large intermediates (Int^L). In two of the three pathways, the leaving ligand (Py*), which is not a component of Tet, catalytically assisted the self-assembly. Such a multiplicity of the self-assembly process of Tet suggests that molecular self-assembly takes place on an energy landscape like a protein-folding funnel.

Quantified structural speciation in self-sorted CoII6L4 cage systems

The molecular components of biological systems self-sort in different ways to function cooperatively and to avoid interfering with each other. Understanding the driving forces behind these different sorting modes enables progressively more complex self-assembling synthetic systems to be designed. Here we show that subtle ligand differences engender distinct M₆L₄ cage geometries - an S₄-symmetric scalenohedron, or pseudo-octahedra having T point symmetry. When two different ligands were simultaneously employed during self-assembly, a mixture of homo- and heteroleptic cages was generated. Each set of product structures represents a unique sorting regime: biases toward specific geometries, preferential incorporation of one ligand over another, and the amplification of homoleptic products were all observed. The ligands' geometries, electronic properties, and flexibility were found to influence the sorting regime adopted, together with templation effects. A new method of using mass spectrometry to quantitatively analyse mixtures of self-sorted assemblies was developed to assess individual outcomes. Product distributions in complex, dynamic mixtures were thus quantified by non-chromatographic methods.

Coordination-driven self-assembly of chiral palladium(ii)-based supramolecular triangle structures

Chiral structures of palladium(ii)-based triangular supramolecular complexes, with achiral corners and edges, have been characterized in solution.

"Breathing" Motion of a Modulable Molecular Cavity

A class of hemicryptophane cages that adopt imploded conformations in solution and in the solid state has been described and studied by NMR spectroscopy and X-ray crystallography. It is reported that the degree of collapse of the molecular cavity can be controlled by changing the stereochemistry of the chiral elements of the hemicryptophanes, leading to a modulation of their physical and chemical properties. Upon the binding of an oxidovanadium unit, the collapsed molecular cavity can inflate to give an expanded conformation. Removal of the vanadium core by an ancillary complexing ligand restores the initial folded structure. Thus, coordination/de-coordination of the metal ion controls the dynamic motions of the cage, leading to a reversible nanomechanical process. This controlled motion between a collapsed and expanded cavity can be seen as that of a breathable molecular cage.

Topological transformation of a trefoil knot into a [2]catenane

Kinetic and thermodynamic investigation of topological transformation of a trefoil knot into a [2]catenane in water.