Gold Catalysis in (Supra)Molecular Cages to Control Reactivity and Selectivity

β-Cyclodextrin-NHC-Au(I)-Catalyzed Enantioconvergent 1,5-Enyne Cycloisomerizations

Enantioconvergent transformations from racemic mixtures are attractive since they allow the generation of optically active products with full conversion despite the possibly adverse kinetic resolution process. When dealing with gold(I)-catalyzed cycloisomerizations, chirality transfer from the precursor is another possible diverting pathway, which renders enantioconvergence challenging. Not surprisingly, enantioconvergent Au(I)-catalyzed processes have remained extremely rare. Herein we show that cavity-driven catalysis using β-cyclodextrin-NHC-Au(I) complexes brings opportunities to conduct highly enantioconvergent cycloisomerizations of 1,5-enynes, -enynols, and, -enynyl esters.

Au(I) complexes installed on a self-assembled peptide efficiently catalyze intramolecular cyclization reactions

Self-assembled peptides are used for diverse applications in the biomedical and technological fields. The morphology and function of the assembled systems are dictated by the peptide sequence and length. In this work, a supramolecular catalyst was obtained upon self-assembly of the diphenylalanine peptide conjugated to a triphenylphosphine Au(I) complex in acetonitrile. The assembled molecules were characterized by spectroscopic techniques and by scanning electron microscopy. The activity of the catalyst was tested on two substrates in cyclization reactions. The morphology and the dimensions of the assembled systems vary depending on the presence of a carboxyl versus an amide C-terminal end. The catalyst efficiently promotes intramolecular cyclization reactions. Results obtained encourage the use of self-assembled peptides for the obtainment of new and efficient catalysts.

Nanogels with Metal-Organic Cages as Functional Crosslinks

A dinuclear metal-organic cage with four acrylate side chains was prepared by self-assembly. Precipitation polymerization of the cage with N-isopropylacrylamide yielded a thermoresponsive nanogel. The host properties of the cage were retained within the gel matrix, endowing the nanogel with the capability to serve as a sorbent for chloride ions in water. Moreover, a heteroleptic cage with the drug abiraterone as co-ligand was integrated into a nanogel. The addition of chloride ions induced a structural rearrangement of the metal-ligand assembly, resulting in the gradual release of abiraterone.

Active and Transfer Learning of High-Dimensional Neural Network Potentials for Transition Metals

Classical molecular dynamics (MD) simulations represent a very popular and powerful tool for materials modeling and design. The predictive power of MD hinges on the ability of the interatomic potential to capture the underlying physics and chemistry. There have been decades of seminal work on developing interatomic potentials, albeit with a focus predominantly on capturing the properties of bulk materials. Such physics-based models, while extensively deployed for predicting the dynamics and properties of nanoscale systems over the past two decades, tend to perform poorly in predicting nanoscale potential energy surfaces (PESs) when compared to high-fidelity first-principles calculations. These limitations stem from the lack of flexibility in such models, which rely on a predefined functional form. Machine learning (ML) models and approaches have emerged as a viable alternative to capture the diverse size-dependent cluster geometries, nanoscale dynamics, and the complex nanoscale PESs, without sacrificing the bulk properties. Here, we introduce an ML workflow that combines transfer and active learning strategies to develop high-dimensional neural networks (NNs) for capturing the cluster and bulk properties for several different transition metals with applications in catalysis, microelectronics, and energy storage, to name a few. Our NN first learns the bulk PES from the high-quality physics-based models in literature and subsequently augments this learning via retraining with a higher-fidelity first-principles training data set to concurrently capture both the nanoscale and bulk PES. Our workflow departs from status-quo in its ability to learn from a sparsely sampled data set that nonetheless covers a diverse range of cluster configurations from near-equilibrium to highly nonequilibrium as well as learning strategies that iteratively improve the fingerprinting depending on model fidelity. All the developed models are rigorously tested against an extensive first-principles data set of energies and forces of cluster configurations as well as several properties of bulk configurations for 10 different transition metals. Our approach is material agnostic and provides a methodology to transfer and build upon the learnings from decades of seminal work in molecular simulations on to a new generation of ML-trained potentials to accelerate materials discovery and design.

Orientational Self-Sorting in Octahedral Palladium Cages: Scope and Limitations of the "cis Rule"

Octahedral coordination cages of the general formula [Pd6L12](BF4)12 were obtained by combining [Pd(CH3CN)4](BF4)2 with heteroditopic N-donor ligands. Four different ligands were employed. These ligands have 3-pyridyl donor groups at one end and 4-pyridyl, imidazolyl, or triazolyl donor groups at the other end. According to a geometric analysis, cages with a cis configuration at the six metal centers should be preferred ("cis rule"). This prediction was corroborated by spectroscopic data and crystallographic analyses. Limitations of the "cis rule" were also encountered, and possible explanations are discussed.

Hydration of Propargyl Esters Catalyzed by Gold(I) Complexes with Phosphoramidite Calix[4]pyrrole Cavitands as Ligands

We report the synthesis and characterization of two diastereomeric phosphoramidite calix[4]pyrrole cavitands and their corresponding gold(I) complexes, 2in•Au(I)•Cl and 2out•Au(I)•Cl, featuring the metal center directed inward and outward with respect to their aromatic cavity. We studied the catalytic activity of the complexes in the hydration of a series of propargyl esters as the benchmarking reaction. All substrates were equipped with a six-membered ring substituent either lacking or including a polar group featuring different hydrogen bond acceptor (HBA) capabilities. We designed the substrates with the polar group to form 1:1 inclusion complexes of different stabilities with the catalysts. In the case of 2in•Au(I)•OTf, the 1:1 complex placed the alkynyl group of the bound substrate close to the metal center. We compared the obtained results with those of a model phosphoramidite gold(I) complex lacking a calix[4]pyrrole cavity. We found that for all catalysts, the presence of an increasingly polar HBA group in the substrate provoked a decrease in the hydration rate constants. We attributed this result to the competing coordination of the HBA group of the substrate for the Au(I) metal center of the catalysts.

Recent advances in porous molecular cages for photocatalytic organic conversions

Photocatalytic organic conversion is considered an efficient, environmentally friendly, and energy-saving strategy for organic synthesis. In recent decades, the molecular cage has emerged as a creative functional material with broad applications in host-guest recognition, drug delivery, catalysis, intelligent materials and other fields. Based on the unique properties of porous molecular cage materials, they provide an ideal platform for leveraging pre-structuring in catalytic reactions and show great potential in various photocatalytic organic reactions. As a result, they have emerged as promising alternatives to conventional molecules or inorganic photocatalysts in redox processes. In this Review, the synthesis strategies based on coordination cages and organic cages, as well as their recent progress in photocatalytic organic conversion, are comprehensively summarized. Finally, we deliver the persistent challenges associated with porous molecular cage compounds that need to be overcome for further development in this field.

A photoresponsive gold catalyst based on azobenzene-functionalized NHC ligands

An azobenzene-bearing N-heterocyclic carbene-based gold catalyst is reported of which the reactivity in a cyclization reaction depends on the isomeric state of the azobenzene. The configurations of the catalyst can be reversibly switched by light and are stable during the reaction, effectively leading to a switchable catalyst system.

Substrate Switchable Pathway for Selective Construction of Bridged Dibenzo[b,f][1,5]diazocines and Bridged Spiromethanodibenzo[b,e]azepines

An operationally simple method for the synthesis of bridged dibenzo[b,f][1,5]diazocines and bridged spiromethanodibenzo[b,e]azepines exhibiting bridged eight-membered and seven-membered molecular architecture is reported. This unique approach is based on substrate selective mechanistic pathway, including an unprecendented aerial oxidation-driven mechanism for the synthesis of bridged spiromethanodibenzo[b,e]azepines. The reaction is highly atom economic, and in addition, it allows the construction of two rings and four bonds in a single operation under metal-free condition. The easy availability of β enaminone and ortho phathalaldehyde as starting materials and the simple operation make this approach suitable for the preparation of important dibenzo[b,f][1,5]diazocine and spiromethanodibenzo[b,e]azepine cores.

Supramolecular Coordination Cages for Artificial Photosynthesis and Synthetic Photocatalysis

Because sunlight is the most abundant energy source on earth, it has huge potential for practical applications ranging from sustainable energy supply to light driven chemistry. From a chemical perspective, excited states generated by light make thermodynamically uphill reactions possible, which forms the basis for energy storage into fuels. In addition, with light, open-shell species can be generated which open up new reaction pathways in organic synthesis. Crucial are photosensitizers, which absorb light and transfer energy to substrates by various mechanisms, processes that highly depend on the distance between the molecules involved. Supramolecular coordination cages are well studied and synthetically accessible reaction vessels with single cavities for guest binding, ensuring close proximity of different components. Due to high modularity of their size, shape, and the nature of metal centers and ligands, cages are ideal platforms to exploit preorganization in photocatalysis. Herein we focus on the application of supramolecular cages for photocatalysis in artificial photosynthesis and in organic photo(redox) catalysis. Finally, a brief overview of immobilization strategies for supramolecular cages provides tools for implementing cages into devices. This review provides inspiration for future design of photocatalytic supramolecular host-guest systems and their application in producing solar fuels and complex organic molecules.

Square-Planar and Octahedral Gyroscope-Like Metal Complexes Consisting of Dipolar Rotators Encased in Dibridgehead Di(triaryl)phosphine Stators: Syntheses, Structures, Dynamic Properties, and Reactivity

For a variety of purposes, it is of interest to embed metals in cagelike trans-spanning di(triaryl)phosphine ligands. Toward this end, a combination of P(p-C₆H₄O(CH₂)_mCH═CH₂)₃ [3; m = 4 (a), 5 (b), 6 (c), and 7 (d)], [Rh(COD)(μ-Cl)]₂, and CO gives square-planar trans-Rh(CO)(Cl)[P(p-C₆H₄O(CH₂)_mCH═CH₂)₃]₂ (4a-4d). Reactions of 4b-4d with Grubbs' catalyst (first generation) and then H₂ (catalyst PtO₂) yield the title compounds trans-Rh(CO)(Cl)[P(p-C₆H₄O(CH₂)_nO-p-C₆H₄)₃P] (n = 2m + 2, 6b-6d; 26-41% from 4b-4d). Two are crystallographically characterized. The Cl-Rh-CO moieties rapidly rotate on the NMR time scale at -120 °C, per the ample clearance provided by the (CH₂)_n segments. Steric interactions with the PC₆H₄O linkages are analyzed. LiC≡CAr displaces the chloride ligand from 6b to give RhC≡CAr adducts (Ar = C₆H₅/p-C₆H₄CH₃, 7b/8b). The ArC≡C-Rh-CO rotator of 7b rapidly rotates on the NMR time scale (-70 °C), but with 8b, the longer p-CH₃C₆H₄C≡C group is confined between two (CH₂)₁₂ bridges, even at 120 °C. Reactions of Re(CO)₅(X) and 3c (140 °C) give octahedral mer,trans-Re(CO)₃(X)[P(p-C₆H₄O(CH₂)₆CH═CH₂)₃]₂ (X = Cl/Br), and metathesis/hydrogenation sequences yield mer,trans-Re(CO)₃(X)[P(p-C₆H₄O(CH₂)₁₄O-p-C₆H₄)₃P]. Reactions of 6c and 6d and excess PMe₃ give the free diphosphines P(p-C₆H₄O(CH₂)_nO-p-C₆H₄)₃P (14c and 14d, 83-75%). The addition of 14d to [Rh(CO)₂(μ-Cl)]₂ reconstitutes 6d (87%). Both in,in and out,out isomers of 14c and 14d are possible, but low-temperature NMR spectra show one set of signals, consistent with rapid homeomorphic isomerizations that turn the molecules inside out. Thermolyses (C₆D₅Br, 140 °C) effect phosphorus inversion to give in,out isomers.

Orientational self-sorting in cuboctahedral Pd cages

Cuboctahedral coordination cages of the general formula [Pd12L24]24+ (L = low-symmetry ligand) were analyzed theoretically and experimentally. With 350 696 potential isomers, the structural space of these assemblies is vast. Orientational self-sorting refers to the preferential formation of particular isomers within the pool of potential structures. Geometric and computational analyses predict the preferred formation of cages with a cis arrangement at the metal centers. This prediction was corroborated experimentally by synthesizing a [Pd12L24]24+ cage with a bridging 3-(4-(pyridin-4-yl)phenyl)pyridine ligand. A crystallographic analysis of this assembly showed exclusive cis coordination of the 3- and the 4-pyridyl donor groups at the Pd2+ ions.

Diametric calix[6]arene gold(I) catalysts for intramolecular cyclopropanations of 1,6-dienynes

We report a solid-state structural investigation of diametric calix[6]arene-based phosphine gold(I) cavitands which are characterised by two specific, different 1,2,3-alternate conformations in solution and in the solid state. The effect of the specific orientation of phosphines, with respect to macrocycles, was studied in intramolecular cyclopropanation of 1,6-dienynes. The general applicability of these catalysts was disclosed, delivering a family of polycycles with high yields and functional group tolerance.

Mimicking Enzymes: Taking Advantage of the Substrate-Recognition Properties of Metalloporphyrins in Supramolecular Catalysis

The present review describes the most relevant advances dealing with supramolecular catalysis in which metalloporphyrins are employed as substrate-recognition sites in the second coordination sphere of the catalyst. The kinetically labile interaction between metallo­porphyrins (typically, those derived from zinc) and nitrogen- or oxygen-containing substrates is energetically comparable to the non-covalent interactions (i.e., hydrogen bonding) found in enzymes enabling substrate preorganization. Much inspired from host–guest phenomena, the catalytic systems described in this account display unique activities, selectivities and action modes that are difficult to reach by applying purely covalent strategies.

Supramolecular Strategies for the Recycling of Homogeneous Catalysts

Supramolecular approaches are increasingly used in the development of homogeneous catalysts and they also provide interesting new tools for the recycling of metal-based catalysts. Various non-covalent interactions have been utilized for the immobilization homogeneous catalysts on soluble and insoluble support. By non-covalent anchoring the supported catalysts obtained can be recovered via (nano-) filtration or such catalytic materials can be used in continuous flow reactors. Specific benefits from the reversibility of catalyst immobilization by non-covalent interactions include the possibility to re-functionalize the support material and the use as "boomerang" type catalyst systems in which the catalyst is captured after a homogeneous reaction. In addition, new reactor design with implemented recycling strategies becomes possible, such as a reverse-flow adsorption reactor (RFA) that combines a homogeneous reactor with selective catalyst adsorption/desorpion. Next to these non-covalent immobilization strategies, supramolecular chemistry can also be used to generate the support, for example by generation of self-assembled gels with catalytic function. Although the stability is a challenging issue, some self-assembled gel materials have been successfully utilized as reusable heterogeneous catalysts. In addition, catalytically active coordination cages, which are frequently used to achieve specific activity or selectivity, can be bound to support by ionic interactions or can be prepared in structured solid materials. These new heterogenized cage materials also have been used successfully as recyclable catalysts.

Just Add Water: Modulating the Structure-Derived Acidity of Catalytic Hexameric Resorcinarene Capsules

The hexameric undecyl-resorcin[4]arene capsule (C11R6) features eight discrete structural water molecules located at the vertices of its cubic suprastructure. Combining NMR spectroscopy with classical molecular dynamics (MD), we identified and characterized two distinct species of this capsule, C11R6-A and C11R6-B, respectively featuring 8 and 15 water molecules incorporated into their respective hydrogen-bonded networks. Furthermore, we found that the ratio of the C11R6-A and C11R6-B found in solution can be modulated by controlling the water content of the sample. The importance of this supramolecular modulation in C11R6 capsules is highlighted by its ability to perform acid-catalyzed transformations, which is an emergent property arising from the hydrogen bonding within the suprastructure. We show that the conversion of C11R6-A to C11R6-B enhances the catalytic rate of a model Diels-Alder cyclization by 10-fold, demonstrating the cofactor-derived control of a supramolecular catalytic process that emulates natural enzymatic systems.

Orientational self-sorting: formation of structurally defined Pd4L8 and Pd6L12 cages from low-symmetry dipyridyl ligands

Tetra- and hexanuclear coordination cages were obtained in reactions of [Pd(CH₃CN)₄](BF₄)₂ with low-symmetry dipyridyl ligands. In both cases, only one structurally defined complex was formed out of a vast pool of potential isomers.

Main Avenues in Gold Coordination Chemistry

In this contribution, we provide an overview of the main avenues that have emerged in gold coordination chemistry during the last years. The unique properties of gold have motivated research in gold chemistry, and especially regarding the properties and applications of gold compounds in catalysis, medicine, and materials chemistry. The advances in the synthesis and knowledge of gold coordination compounds have been possible with the design of novel ligands becoming relevant motifs that have allowed the preparation of elusive complexes in this area of research. Strong donor ligands with easily modulable electronic and steric properties, such as stable singlet carbenes or cyclometalated ligands, have been decisive in the stabilization of gold(0) species, gold fluoride complexes, gold hydrides, unprecedented π complexes, or cluster derivatives. These new ligands have been important not only from the fundamental structure and bonding studies but also for the synthesis of sophisticated catalysts to improve activity and selectivity of organic transformations. Moreover, they have enabled the facile oxidative addition from gold(I) to gold(III) and the design of a plethora of complexes with specific properties.

Catalytic Gold Chemistry: From Simple Salts to Complexes for Regioselective C-H Bond Functionalization

Gold coordinated to neutral phosphines (R₃ P), N-heterocyclic carbenes (NHCs) or anionic ligands is catalytically active in functionalizing various C-H bonds with high selectivity. The sterics/electronic nature of the studied C-H bond, oxidation state of gold and stereoelectronic capacity of the coordinated auxiliary ligand are some of the associated selectivity factors in gold-catalyzed C-H bond functionalization reactions. Hence, in this review a comprehensive update about the action of different types of gold catalysts, from simple to sophisticated ones, on C-H bond reactions and their regiochemical outcome is disclosed. This review also highlights the catalytic applications of Au(I)- and Au(III)-species in creating new opportunities for the regio- and site-selective activation of challenging C-H bonds. Finally, it also intends to stress the potential applications in selective C-H bond activation associated with a variety of heterocycles recently described in the literature.

Merging Molecular Recognition and Gold(I) Catalysis with Triphoscalix[6]arene Ligands

We report the synthesis and characterization of novel triphosphine calix[6]arene ligands. These supramolecular wheels, with recognition features governed by the hydrogen-bonding domain, were employed to synthesize multitasking trinuclear gold(I) complexes as a new platform for the synthesis of interwoven (pseudo)rotaxane species. In parallel, the multivalent, metal-bonded upper rim displayed catalytic features promoting highly selective gold-catalyzed cycloisomerization reactions of 1,6-enynes.

New horizons for catalysis disclosed by supramolecular chemistry

The adoption of a supramolecular approach in catalysis promises to address a number of unmet challenges, ranging from activity (unlocking of novel reaction pathways) to selectivity (alteration of the innate selectivity of a reaction, e.g. selective functionalization of C-H bonds) and regulation (switch ON/OFF, sequential catalysis, etc.). Supramolecular tools such as reversible association and recognition, pre-organization of reactants and stabilization of transition states upon binding offer a unique chance to achieve the above goals disclosing new horizons whose potential is being increasingly recognized and used, sometimes reaching the degree of ripeness for practical use. This review summarizes the main developments that have opened such new frontiers, with the aim of providing a guide to researchers approaching the field. We focus on artificial supramolecular catalysts of defined stoichiometry which, under homogeneous conditions, unlock outcomes that are highly difficult if not impossible to attain otherwise, namely unnatural reactivity or selectivity and catalysis regulation. The different strategies recently explored in supramolecular catalysis are concisely presented, and, for each one, a single or very few examples is/are described (mainly last 10 years, with only milestone older works discussed). The subject is divided into four sections in light of the key design principle: (i) nanoconfinement of reactants, (ii) recognition-driven catalysis, (iii) catalysis regulation by molecular machines and (iv) processive catalysis.

Base-Catalyzed, Solvent-Free Synthesis of Rigid V-Shaped Epoxydibenzo[b,f][1,5]diazocines

A novel method for the synthesis of epoxydibenzo[b,f][1,5]diazocines exhibiting a V-shaped molecular architecture is reported. The unique approach is based on unprecedented base-catalyzed, solvent-free autocondensation and cross-condensation of fluorinated o-aminophenones. The structure of the newly synthesized diazocines was confirmed independently by X-ray analysis and chiroptical methods. The rigidity of the diazocine scaffold allowed for the separation of the racemate into single enantiomers that proved to be thermally stable up to 140 °C. Furthermore, the inertness of the diazocine scaffold was demonstrated by performing a series of typical transformations, including transition metal-catalyzed reactions, proceeding without affecting the bis-hemiaminal subunit.

Tuning the Size and Geometry of Heteroleptic Coordination Cages by Varying the Ligand Bent Angle

Spherical assemblies of the type [Pd_n L_2n ]²ⁿ⁺ can be obtained from Pd^II salts and curved N-donor ligands, L. It is well established that the bent angle, α, of the ligand is a decisive factor in the self-assembly process, with larger angles leading to complexes with a higher nuclearity, n. Herein, we report heteroleptic coordination cages of the type [Pd_n L_n L'_n ]²ⁿ⁺ , for which a similar correlation between the ligand bent angle and the nuclearity is observed. Tetranuclear cages were obtained by combining [Pd(CH₃ CN)₄ ](BF₄ )₂ with 1,3-di(pyridin-3-yl)benzene and ligands featuring a bent angle of α=120°. The use of a dipyridyl ligand with α=149° led to the formation of a hexanuclear complex with a trigonal prismatic geometry; for linear ligands, octanuclear assemblies of the type [Pd₈ L₈ L'₈ ]¹⁶⁺ were obtained. The predictable formation of heteroleptic Pd^II cages from 1,3-di(pyridin-3-yl)benzene and different dipyridyl ligands is evidence that there are entire classes of heteroleptic cage structures that are privileged from a thermodynamic point of view.

Cycloisomerization of π-Coupled Heteroatom Nucleophiles by Gold Catalysis: En Route to Regiochemically Defined Heterocycles

Since the dawn of millennium, catalytic gold chemistry is at the forefront to set off diverse organic reactions via unique activation of π-bonded molecules. Within this purview, cycloisomerization of heteroatom nucleophiles linked to a π-system is one of the well recognized chemistry for the construction of numerous heterocyclic cores. Though the rudimentary aspects of this transformation are reviewed by several groups in different timeline, a holistic view on regiochemistry of such reactions went largely overlooked. Hence, this account emphasizes the gold catalyzed regioselective cycloisomerization of structurally distinctive π-connected hetero-nucleophiles leading to different heterocycles documented in the last two decades. From an application perspective, this account also highlights those methodologies which find a role in the total synthesis of natural products. Wherever appropriate, mechanistic details and contributing factors for selectivity are also discussed.

Enantioselective Alkoxycyclization of 1,6-Enynes with Gold(I)-Cavitands: Total Synthesis of Mafaicheenamine C

Chiral gold(I)-cavitand complexes have been developed for the enantioselective alkoxycyclization of 1,6-enynes. This enantioselective cyclization has been applied for the first total synthesis of carbazole alkaloid (+)-mafaicheenamine C and its enantiomer, establishing its configuration as R. The cavity effect was also evaluated in the cycloisomerization of dienynes. A combination of experiments and theoretical studies demonstrates that the cavity of the gold(I) complexes forces the enynes to adopt constrained conformations, which results in the high observed regio- and stereoselectivities.

A non-ionic surfactant based catalyst tablet: a reusable gold–NHC catalyst system for alkyne hydration reactions

Herein, we report the encapsulation of IPrAuCl (Au-1) in Synperonic®F108 (Syn), acting as both a catalyst tablet medium and surfactant for dispersion of hydrophobic alkyne substrates and gold–NHC complexes in aqueous media.

Topological prediction of palladium coordination cages

The preparation of functionalized, heteroleptic Pd_xL_2x coordination cages is desirable for catalytic and optoelectronic applications. Current rational design of these cages uses the angle between metal-binding (∠B) sites of the di(pyridyl)arene linker to predict the topology of homoleptic cages obtained via non-covalent chemistry. However, this model neglects the contributions of steric bulk between the pyridyl residues—a prerequisite for endohedrally functionalized cages, and fails to rationalize heteroleptic cages. We describe a classical mechanics (CM) approach to predict the topological outcomes of Pd_xL_2x coordination cage formation with arbitrary linker combinations, accounting for the electronic effects of coordination and steric effects of linker structure. Initial validation of our CM method with reported homoleptic Pd₁₂LFu₂₄ (LFu = 2,5-bis(pyridyl)furan) assembly suggested the formation of a minor topology Pd₁₅LFu₃₀, identified experimentally by mass spectrometry. Application to heteroleptic cage systems employing mixtures of LFu (∠B = 127°) and its thiophene congener LTh (∠B = 149° ∠B_exp = 152.4°) enabled prediction of Pd₁₂L₂₄ and Pd₂₄L₄₈ coordination cages formation, reliably emulating experimental data. Finally, the topological outcome for exohedrally (LEx) and endohedrally (LEn) functionalized heteroleptic Pd_xL_2x coordination cages were predicted to assess the effect of steric bulk on both topological outcomes and coordination cage yields, with comparisons drawn to experimental data.

A molecular mechanics approach enables the accurate prediction of polyhedral topology for homoleptic and heteroleptic palladium M_xL_2x coordination cages, allowing for new insight and design when considering endo- and exo-hedral functionalization.

Au-Cavitands: Size governed arene-alkyne cycloisomerization

With an inwardly directed reactive center and a well-defined binding pocket, Au(I) functionalized resorcin[4]arene cavitands have been shown to catalyze molecular transformations. The reactivity profiles that emerge differ from other Au(I) catalysts. The added constraint of a binding pocket gives rise to the possibility that the substrates might have to fit into the resorcinarene pocket; our hypothesis is that substrates that match the available space have different reaction outcomes than those that do not. Herein we report on the intramolecular cyclization of alkyne-aromatic substrates with variable alkynes and aromatic composition. We see that scaffold size most drastically dictates reactivity, especially when the substrate's features are particularly designed. The results of these experiments add to the veritable goldmine of information about the selectivity in catalysis that cavitands offer.

Photochromic organic cage-encapsulated Au nanoparticles: light-regulated cavities for catalytic reduction of 4-nitrophenol

Encapsulated Au nanoparticles in a diarylethene-based photochromic cage with adjustable particle sizes under UV and visible light exhibited different catalytic rates for the reduction of 4-nitrophenol.

Confinement of a Au–N-heterocyclic carbene in a Pd6L12 metal–organic cage

A Au(i)–N-heterocyclic-carbene (NHC)-edged Pd₆L₁₂ molecular metal–organic cage is assembled from a Au(i)–NHC-based bipyridyl bent ligand and Pd²⁺. The octahedral cage structure is unambiguously established by NMR, electrospray ionization-mass spectrometry and single crystal X-ray crystallography. The electrochemical behaviour was analyzed by cyclic voltammetry. The octahedral cage has a central cavity for guest binding, and is capable of encapsulating PF₆⁻ and BF₄⁻ anions within the cavity.

A Au(i)–NHC-edged Pd₆L₁₂ molecular cage is assembled from a Au(i)–NHC-based bipyridyl bent ligand and Pd²⁺.