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Controlled preparation of ultrafine metal nanoclusters (<2 nm) is challenging, yet important as the properties of these clusters are inherently linked to their size and local microenvironment. In the present work, we report the utilization of supramolecular pre-organization of organometallic complexes within well-defined M 12 L 24 coordination spheres for the controlled synthesis of ultrafine Ir nanoclusters by reduction with molecular hydrogen. For this purpose, 24 sulfonate functionalized N-heterocyclic carbene (NHC) Ir complexes (Ir-s) were bound within a well-defined M 12 L 24 nanosphere that is equipped with 24 guanidinium binding sites (G-sphere). Reduction of these pre-organized metal complexes by hydrogenation led to the templated formation of nanoclusters with a narrow size distribution (1.8 ± 0.4 nm in diameter). It was demonstrated through 1 H-DOSY-NMR and HAADF-STEM-EDX experiments that the resulting nanoclusters reside within the nanospheres. The reduction of similar non-encapsulated metal complexes in the presence of nanosphere systems (Ir-s + M-sphere or Ir-p + G-sphere) resulted in larger particles with a broader size distribution (2.3 ± 2.1 nm and 6.6 ± 3.2 nm for Ir-s + M-sphere and Ir-p + G-sphere respectively). The encapsulated nanoclusters were used as a homogeneous catalyst in the selective hydrogenation of 4-nitrostyrene to 4-ethylnitrobenzene and display absolute selectivity, which is even maintained at full conversions, whereas the larger non-encapsulated clusters were less selective as these also showed reduction of the nitro functionality., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Supramolecular polymer networks contain non-covalent cross-links that enable access to broadly tunable mechanical properties and stimuli-responsive behaviors; the incorporation of multiple unique non-covalent cross-links within such materials further expands their mechanical responses and functionality. To date, however, the design of such materials has been accomplished through discrete combinations of distinct interaction types in series, limiting materials design logic. Here we introduce the concept of leveraging "nested" supramolecular crosslinks, wherein two distinct types of non-covalent interactions exist in parallel, to control bulk material functions. To demonstrate this concept, we use polymer-linked Pd 2 L 4 metal-organic cage (polyMOC) gels that form hollow metal-organic cage junctions through metal-ligand coordination and can exhibit well-defined host-guest binding within their cavity. In these "nested" supramolecular network junctions, the thermodynamics of host-guest interactions within the junctions affect the metal-ligand interactions that form those junctions, ultimately translating to substantial guest-dependent changes in bulk material properties that could not be achieved in traditional supramolecular networks with multiple interactions in series., (© 2024. The Author(s).)

Grafting molecular complexes on solid supports is a facile strategy to synthesize advanced materials. Here, we present a general and simple method for noncovalent grafting on charge-neutral surfaces. Our method is based on the generic principle of counterion confinement in surface micropores. We demonstrate the power of this approach using a set of three platinum complexes: Pt 1 (Pt 1 L 4 (BF 4 ) 2 , L = p -picoline), Pt 2 (Pt 2 L 4 (BF 4 ) 4 , L = 2,6-bis(pyridine-3-ylethynyl)pyridine), and Pt 12 (Pt 12 L 24 (BF 4 ) 24 , L = 4,4'-(5-methoxy-1,3-phenylene)dipyridine). These complexes share the same counterion (BF 4 - ) but differ vastly in their size, charge, and structure. Imaging of the grafted materials by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) and energy-dispersive X-ray (EDX) showed that our method results in a homogeneous distribution of both complexes and counterions. Nitrogen sorption studies indicated a decrease in the available surface area and micropore volume, providing evidence for counterion confinement in the surface micropores. Following the adsorption of the complexes over time showed that this is a two-step process: fast surface adsorption by van der Waals forces was followed by migration over the surface and surface binding by counterion confinement. Regarding the binding of the complexes to the support, we found that the surface-adsorbate binding constant ( K S ) increases quadratically with the number of anions per complex up to K S = 1.6 × 10 6 M -1 equaling Δ G ° ads = -35 kJ mol -1 for the surface binding of Pt 12 . Overall, our method has two important advantages: first, it is general, as you can anchor different complexes (with different charges, counterions, and/or sizes); second, it promotes the distribution of the complexes on the support surface, creating well-distributed sites that can be used in various applications across several areas of chemistry., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Controlling the coordination sphere of heterogeneous single-metal-site catalysts is a powerful strategy for fine-tuning their catalytic properties but is fairly difficult to achieve. To address this problem, we immobilized supramolecular cages where the primary- and secondary coordination sphere are controlled by ligand design. The kinetics of these catalysts were studied in a model reaction, the hydrolysis of ammonia borane, over a temperature range using fast and precise online measurements generating high-precision Arrhenius plots. The results show how catalytic properties can be enhanced by placing a well-defined reaction pocket around the active site. Our fine-tuning yielded a catalyst with such performance that the reaction kinetics are diffusion-controlled rather than chemically controlled., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Metal-organic cages/polyhedra (MOCs) are versatile building blocks for advanced polymer networks with properties that synergistically blend those of traditional polymers and crystalline frameworks. Nevertheless, constructing polyMOCs from very stable Pt(II)-based MOCs or mixtures of metal ions such as Pd(II) and Pt(II) has not, to our knowledge, been demonstrated, nor has exploration of how the dynamics of metal-ligand exchange at the MOC level may impact bulk polyMOC energy dissipation. Here, we introduce a new class of polymer metal-organic cage (polyMOC) gels featuring polyethylene glycol (PEG) strands of varied length cross-linked through bis-pyridyl-carbazole-based M 6 L 12 cubes, where M is Pd(II), Pt(II), or mixtures thereof. We show that, while polyMOCs with varied Pd(II) content have similar network structures, their average stress-relaxation rates are tunable over 3 orders of magnitude due to differences in Pd(II)- and Pt(II)-ligand exchange rates at the M 6 L 12 junction level. Moreover, mixed-metal polyMOCs display relaxation times indicative of intrajunction cooperative interactions, which stands in contrast to previous materials based on point metal junctions. Altogether, this work (1) introduces a novel MOC architecture for polyMOC design, (2) shows that polyMOCs can be prepared from mixtures of Pd(II)/Pt(II), and (3) demonstrates that polyMOCs display unique relaxation behavior due to their multivalent junctions, offering a strategy for controlling polyMOC properties independently of their polymer components.

In this contribution, we describe a post-assembly modification approach to selectively coordinate transition metals in Pd 12 L 24 cuboctahedra. The herein reported approach involves the preparation of Pd 12 L 24 nanospheres with protonated nitrogen donor ligands that are covalently linked at the interior. The so obtained Pd 12 (LH + ) 24 nanospheres are shown to be suitable for coordinative post-modification after deprotection by deprotonation. Selective formation of tetra-coordinated M B in Pd 12 M B 6 L 24 , tri-coordinated M B in Pd 12 M B 8 L 24 nanospheres and two-coordinated M B in Pd 12 M B 12 L 24 nanospheres is achieved as a result of different nitrogen donor ligands. A combination of pulsed EPR spectroscopy (DEER) to measure Cu-Cu distances in the different spheres, NMR studies and computational investigations, support the presence of the complexes at precise locations of the Pd 12 M B 6 L 24 nanosphere. The general post-assembly modification methodology can be extended using other transition metal precursors or supramolecular systems and can guide precise formation and investigation of novel transition metal-complex containing nanospheres with well-defined composition., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Supramolecular cages have received tremendous attention as they can contain catalysts that exhibit confinement effects in the cavity, leading to excellent performances. Herein, we report an example wherein the catalytic region is extended from the cage cavity to the windows, and investigate its confinement effect by utilizing the Pd 6 L Au 12 cage that contains rigidly fixed and isolated gold complexes at the windows. Pd 6 L Au 12 exhibit three features of particular interest while assessing their properties in gold-catalyzed cyclization reactions. First, the catalysts experience a cage effect as they display higher reactivity and selectivity compared to the monomeric analogue, as a result of substrate pre-organization at the windows. Second, the metal complexes are physically separated by the cage structure, preventing the formation of less active dinuclear gold complexes making it more stable under hydrous conditions. Third, the cage windows present the characteristics of enzymatic catalysis via Michaelis-Menten-type mechanism analysis. This contribution presents an alternative way to engineer supramolecular catalysts through extending the catalytic region., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The concentrations of reactive oxygen species (ROS), e.g., H 2 O 2 , are often elevated in diseased tissue microenvironments. Therefore, the selective detection of ROS could enable new diagnostic methods or tools for chemical biology. Here, we report the synthesis of boronic ester-bis-norbornene core-cross-linked brush-arm star polymers (BASPs) with polyethylene glycol (PEG) or PEG- branch -spirocyclohexyl nitroxide (chex) shells. Size exclusion chromatography (SEC) and dynamic light scattering (DLS) showed that these BASPs have narrowly dispersed molar masses and average hydrodynamic diameters of 23 ± 2 nm, respectively. Moreover, due to their core-shell structures, these BASPs disassemble into bottlebrush fragments with improved selectivity for H 2 O 2 over ROS such as peroxynitrite (ONOO - ) and hypochlorite ( - OCl). Finally, H 2 O 2 induced disassembly of chex-containing BASPs induces a change in transverse magnetic relaxivity that can be detected via magnetic resonance imaging (MRI). Chex-BASPs may represent a valuable new diagnostic tool for H 2 O 2 sensing.

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.

The enantioselective hydrogenation of cyclic enamides has been achieved using an earth-abundant cobalt-bisphosphine catalyst. Using CoCl 2 /(S,S)-Ph-BPE, several trisubstituted carbocyclic enamides were reduced with high activity and excellent enantioselectivity (up to 99 %) to the corresponding saturated amides. The methodology can be extended to the synthesis of chiral amines by base hydrolysis of the hydrogenation products. Preliminary mechanistic investigations reveal the presence of a high spin cobalt (II) species in the catalytic cycle. We propose that the hydrogenation of the carbon-carbon double bond proceeds via a sigma-bond-metathesis pathway., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

There is an increasing interest in the application of metal-organic cages (MOCs) in a biomedicinal context, as they can offer non-classical distribution in organisms compared to molecular substrates, while revealing novel cytotoxicity mechanisms. Unfortunately, many MOCs are not sufficiently stable under in vivo conditions, making it difficult to study their structure-activity relationships in living cells. As such, it is currently unclear whether MOC cytotoxicity stems from supramolecular features or their decomposition products. Herein, we describe the toxicity and photophysical properties of highly-stable rhodamine functionalized platinum-based Pt 2 L 4 nanospheres as well as their building blocks under in vitro and in vivo conditions. We show that in both zebrafish and human cancer cell lines, the Pt 2 L 4 nanospheres demonstrate reduced cytotoxicity and altered biodistribution within the body of zebrafish embryos compared to the building blocks. We anticipate that the composition-dependent biodistribution of Pt 2 L 4 spheres together with their cytotoxic and photophysical properties provides the fundament for MOC application in cancer therapy., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

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 L 3 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 L 3 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 L 3 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 L 3 cages formed in enantiomeric pairs., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Metabolic pathways are highly regulated by effector molecules that influences the rate of enzymatic reactions. Inspired by the catalytic regulation found in living cells, we report a Pt 2 L 4 cage of which the activity can be controlled by effectors that bind inside the cage. The cage shows catalytic activity in the lactonization of alkynoic acids, with the reaction rates dependent on the effector guest bound in the cage. Some effector guests enhance the rate of the lactonization by up to 19-fold, whereas one decreases it by 5-fold. When mixtures of specific substrates are used, both starting materials and products act as guests for the Pt 2 L 4 cage, enhancing its catalytic activity for one substrate while reducing its activity for the other. The reported regulatory behavior obtained by the addition of effector molecules paves the way to the development of more complex, metabolic-like catalyst systems., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Spherical three-dimensional (3D) cages composed of palladium(II) and pyridyl ligands are a mainstay of supramolecular chemistry with demonstrated catalytic and optoelectronic applications. The widely reported self-assembly of these palladium-based cages exhibits sensitivity to the solvents, reagents, and/or reactants employed. This sensitivity, and the resulting inconsistency between synthetic protocols, hinders the development of desirable palladium-based cages. We have found that pyridyl ligand substitution─the rate-limiting step of self-assembly─is facilitated by endogenous supporting ligands derived from the solvents, reagents, and reactants employed in synthetic protocols of palladium- and platinum-based assemblies. Here, we present a systematic investigation combining 1 H-NMR, electrospray ionization mass spectrometry (ESI─MS), and absorption spectroscopy to characterize the intermediates to support the mechanism of pyridyl ligand substitution on a model complex, M ( py ) 2 ( M = ( N,N,N ', N '-tetramethylethylenediamine)palladium(II), py = pyridine), under simulated synthetic conditions for self-assembly. Our investigation exposes mechanisms for pyridyl ligand substitution, featuring intermediates stabilized by solvent, anion, or ( in situ formed) alkoxide moieties. Interrogation of destabilizing agents (2,2,2-trifluoroethanol and tetra( n -butyl)ammonium chloride) reveal similar mechanisms that ultimately facilitate the self-assembly of coordination cages. These findings rationalize widely reported solvent and anion effects in the self-assembly of coordination cages (and similar constructs) while highlighting methodologies to understand the role of supporting ligands in coordination chemistry.

Polyureas have widespread applications due to their unique material properties. Because of the toxicity of isocyanates, sustainable isocyanate-free routes to prepare polyureas are a field of active research. Current routes to isocyanate-free polyureas focus on constructing the urea moiety in the final polymerizing step. In this study we present a new isocyanate-free method to produce polyureas by Ru-catalyzed carbene insertion into the N-H bonds of urea itself in combination with a series of bis-diazo compounds as carbene precursors. The mechanism was investigated by kinetics and DFT studies, revealing the rate-determining step to be nucleophilic attack on a Ru-carbene moiety by urea. This study paves the way to use transition-metal-catalyzed reactions in alternative routes to polyureas., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Singlet oxygen is a potent oxidant with major applications in organic synthesis and medicinal treatment. An efficient way to produce singlet oxygen is the photochemical generation by fullerenes which exhibit ideal thermal and photochemical stability. In this contribution we describe readily accessible M 6 L 12 nanospheres with unique binding sites for fullerenes located at the windows of the nanospheres. Up to four C 70 can be associated with a single nanosphere, presenting an efficient method for fullerene extraction and application. Depending on the functionality located on the outside of the sphere, they act as vehicles for 1 O 2 generation in organic or in aqueous media using white LED light. Excellent productivity in 1 O 2 generation and consecutive oxidation of 1 O 2 acceptors using C 70 ⊂[Pd 6 L 12 ], C 60 ⊂[Pd 6 L 12 ] or fullerene soot extract was observed. The methodological design principles allow preparation and application of highly effective multifullerene binding spheres.

The self-assembly of palladium-based cages is frequently rationalized via the cumulative enthalpy (Δ H ) of bonds between coordination nodes (M, i.e. , Pd) and ligand (L) components. This focus on enthalpic rationale limits the complete understanding of the Gibbs free energy (Δ G ) for self-assembly, as entropic (Δ S ) contributions are overlooked. Here, we present a study of the M 2 lin L 3 intermediate species (M = dinitrato( N , N , N ', N '-tetramethylethylenediamine)palladium(ii), lin L = 4,4'-bipyridine), formed during the synthesis of triangle-shaped (M 3 lin L 3 ) and square-shaped (M 4 lin L 4 ) coordination macrocycles. Thermochemical analyses by variable temperature (VT) 1 H-NMR revealed that the M 2 lin L 3 intermediate exhibited an unfavorable (relative) Δ S compared to M 3 lin L 3 (triangle, Δ T Δ S = +5.22 kcal mol -1 ) or M 4 lin L 4 (square, Δ T Δ S = +2.37 kcal mol -1 ) macrocycles. Further analysis of these constructs with molecular dynamics (MD) identified that the self-assembly process is driven by Δ G losses facilitated by increases in solvation entropy (Δ S solv , i.e. , depletion of solvent accessible surface area) that drives the self-assembly from "open" intermediates toward "closed" macrocyclic products. Expansion of our computational approach to the analysis of self-assembly in Pd n ben L 2 n cages ( ben L = 4,4'-(5-ethoxy-1,3-phenylene)dipyridine), demonstrated that Δ S solv contributions drive the self-assembly of both thermodynamic cage products ( i.e. , Pd 12 ben L 24 ) and kinetically-trapped intermediates ( i.e. , Pd 8 c L 16 )., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Square-planar cobalt(II) systems have emerged as powerful carbene transfer catalysts for the synthesis of numerous (hetero)cyclic compounds via cobalt(III)-carbene radical intermediates. Spectroscopic detection and characterization of reactive carbene radical intermediates is limited to a few scattered experiments, centered around monosubstituted carbenes. Here, we reveal the formation of disubstituted cobalt(III)-carbene radicals derived from a cobalt(II)-tetraphenylporphyrin complex and acceptor-acceptor λ 3 -iodaneylidenes (iodonium ylides) as carbene precursors and their catalytic application. Iodonium ylides generate biscarbenoid species via reversible ligand modification of the paramagnetic cobalt(II)-tetraphenylporphyrin complex catalyst. Two interconnected catalytic cycles are involved in the overall mechanism, with a monocarbene radical and an N-enolate-carbene radical intermediate at the heart of each respective cycle. Notably, N-enolate formation is not a deactivation pathway but a reversible process, enabling transfer of two carbene moieties from a single N-enolate-carbene radical intermediate. The findings are supported by extensive experimental and computational studies., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Novel seven-membered cyclic imine-based 1,3-P,N ligands were obtained by capturing a Beckmann nitrilium ion intermediate generated in situ from cyclohexanone with benzotriazole, and then displacing it by a secondary phosphane under triflic acid promotion. These "cycloiminophosphanes" possess flexible non-isomerizable tetrahydroazepine rings with a high basicity; this sets them apart from previously reported iminophophanes. The donor strength of the ligands was investigated by using their P-κ 1 - and P,N-κ 2 -tungsten(0) carbonyl complexes, by determining the IR frequency of the trans-CO ligands. Complexes with [RhCp*Cl 2 ] 2 demonstrated the hemilability of the ligands, giving a dynamic equilibrium of κ 1 and κ 2 species; treatment with AgOTf gives full conversion to the κ 2 complex. The potential for catalysis was shown in the Ru II -catalyzed, solvent-free hydration of benzonitrile and the Ru II - and Ir I -catalyzed transfer hydrogenation of cyclohexanone in isopropanol. Finally, to enable access to asymmetric catalysts, chiral cycloiminophosphanes were prepared from l-menthone, as well as their P,N-κ 2 -Rh III and a P-κ 1 -Ru II complexes., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The sialic acid N-acetylneuraminic acid (Neu5Ac) and its derivatives are involved in many biological processes including cell-cell recognition and infection by influenza. Molecules that can recognize Neu5Ac might thus be exploited to intervene in or monitor such events. A key obstacle in this development is the sparse availability of easily prepared molecules that bind to this carbohydrate in its natural solvent; water. Here, we report that the carbohydrate binding pocket of an organic soluble [Pd 2 L 4 ] 4+ cage could be equipped with guanidinium-terminating dendrons to give the water soluble [Pd 2 L 4 ][NO 3 ] 16 cage 7. It was shown by means of NMR spectroscopy that 7 binds selectively to anionic monosaccharides and strongest to Neu5Ac with K a =24 M -1 . The cage had low to no affinity for the thirteen neutral saccharides studied. Aided by molecular modeling, the selectivity for anionic carbohydrates such as Neu5Ac could be rationalized by the presence of charge assisted hydrogen bonds and/or the presence of a salt bridge with a guanidinium solubilizing arm of 7. Establishing that a simple coordination cage such as 7 can already selectively bind to Neu5Ac in water paves the way to improve the stability, affinity and/or selectivity properties of M 2 L 4 cages for carbohydrates and other small molecules., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Supramolecular coordination-based self-assembled nanostructures have been widely studied, and currently various applications are being explored. For several applications, the stability of the nanostructure is of key importance, and this strongly depends on the metal used in the self-assembly process. Herein, design strategies and synthetic protocols to access desirable kinetically stable Pt 12 L 24 nanospheres are reported, and it is demonstrated that these are stable under conditions under which the palladium counterparts decompose. Descriptors previously used for palladium nanospheres are insufficient for platinum analogues, as the stronger metal-ligand bond results in a mixture of kinetically trapped structures. We report that next to the dihedral angle, the rigidity of the ditopic ligand is also a key parameter for the controlled formation of Pt 12 L 24 nanospheres. Catalytic amounts of coordinating additives to labilise the platinum-pyridyl bond to some extent are needed to selectively form Pt 12 L 24 assemblies. The formed Pt 12 L 24 nanospheres were demonstrated to be stable in the presence of chloride, amines and acids, unlike the palladium analogues., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The dynamics of metal organic polyhedra (MOP) play a crucial role for their application in catalysis and host-guest chemistry and as functional materials. In this contribution, we study the influence of possible contaminations of different metal precursors on the kinetic properties of MOP. Exemplary five different MOP are studied with metal precursors of varying quality. The metal precursors are either obtained from commercial sources or prepared by various literature procedures. Studies into the self-assembly process using 1 H NMR and MS analyses were performed on Pt 2 L 4 , Pd 2 L 4 , Pd 6 L 12 , Pd 12 L 24 , and Ni 4 L 6 assemblies. Commonly found impurities are shown to play a prominent role guiding selective formation of MOP, as they allow for an escape from otherwise kinetically trapped intermediates. The energy requirement for selective sphere formation is significantly lowered in many examples providing evidence for a catalytic role of halide impurities/additives in the self-assembly process. Furthermore, even though most analytical features such as 1 H NMR and MS analyses show identical results for assemblies with different types of metal precursors, the dynamics of formed assemblies differs significantly if slightly less pure starting materials are used. Tiny amounts of halide contaminations make the MOP more dynamic, which can play an important role for substrate diffusion especially if bulky substrates are used. We believe that this study on the influence of impurities (which were shown to be present in some commercial sources) on the kinetic properties of MOP together with procedures of obtaining high purity metal precursors provides important information for future material preparation and provides a better understanding of already known examples.

Two dipyridyl ligands were synthesized, where the pyridyl donor fragments were separated by an isophthalamide (1) or a dipicolinamide moiety (2). Both ligands formed [Pd2(Ligand)4][BF4]4 complexes in CD2Cl2 containing 5% dmso-d6. It was found that while [Pd2(1)4][BF4]4 readily binds to n-octyl glycosides and to nitrate anions, [Pd2(2)4][BF4]4 did not. The difference in binding properties could be rationalized based on the reduced flexibility and size of the [Pd2(2)4]2+ cage and/or stronger interior binding of a BF4- counter anion.

Designing compounds for the selective molecular recognition of carbohydrates is a challenging task for supramolecular chemists. Macrocyclic compounds that incorporate isophtalamide or bisurea spacers linking two aromatic moieties have proven effective for the selective recognition of all-equatorial carbohydrates. Here, we explore the molecular recognition properties of an octa-urea [Pd 2 L 4 ] 4+ cage complex (4). It was found that small anions like NO 3 - and BF 4 - bind inside 4 and inhibit binding of n-octyl glycosides. When the large non-coordinating anion 'BAr F ' was used, 4 showed excellent selectivity towards n-octyl-α-D-Mannoside with binding in the order of K a ≈16 M -1 versus non-measurable affinities for other glycosides including n-octyl-β-D-Glucoside (in CH 3 CN/H 2 O 91 : 9)., (© 2021 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

Confinement of a catalyst can have a significant impact on catalytic performance and can lead to otherwise difficult to achieve catalyst properties. Herein, we report the design and synthesis of a novel caged catalyst system Co-G@Fe 8 (Zn-L ⋅ 1) 6 , which is soluble in both polar and apolar solvents without the necessity of any post-functionalization. This is a rare example of a metal-coordination cage able to bind catalytically active porphyrins that is soluble in solvents spanning a wide variety of polarity. This system was used to investigate the combined effects of the solvent and the cage on the catalytic performance in the cobalt catalyzed cyclopropanation of styrene, which involves radical intermediates. Kinetic studies show that DMF has a protective influence on the catalyst, slowing down deactivation of both [Co(TPP)] and Co-G@Fe 8 (Zn-L ⋅ 1) 6 , leading to higher TONs in this solvent. Moreover, DFT studies on the [Co(TPP)] catalyst show that the rate determining energy barrier of this radical-type transformation is not influenced by the coordination of DMF. As such, the increased TONs obtained experimentally stem from the stabilizing effect of DMF and are not due to an intrinsic higher activity caused by axial ligand binding to the cobalt center ([Co(TPP)(L)]). Remarkably, encapsulation of Co-G led to a three times more active catalyst than [Co(TPP)] (TOF ini ) and a substantially increased TON compared to both [Co(TPP)] and free Co-G. The increased local concentration of the substrates in the hydrophobic cage compared to the bulk explains the observed higher catalytic activities., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Supramolecular self-assemblies are used across various fields for different applications including their use as containers for catalysts, drugs and fluorophores. M 12 L 24 spheres are among the most studied, as they offer plenty of space for functionalization, yielding systems with unique properties in comparison to their single components. Detailed studies on the formation of M 12 L 24 structures using palladium cornerstones (that have generally dynamic coordination chemistry) aided in the development of synthetic protocols. The more robust platinum-based systems received thus far much less attention. The general use of platinum-based assemblies remains elusive as parameters and design principles of the ligand building blocks are not fully established. As platinum-based nanospheres are more robust due to the kinetically more stable nitrogen-platinum bond, we studied the sphere formation process in detail in order to develop descriptors for the formation of platinum-based nanospheres. In a systematic study, using time-dependent mass spectrometry, 1 H-NMR and DOSY NMR, we identified new kinetically trapped intermediates during the formation of Pt 12 L 24 spheres and we developed key parameters for selective formation of Pt 12 L 24 spheres. Molecular mechanics calculations and experimental result support the importance of charge and steric bulk placed at the endo -site of the ditopic linker for selective sphere formation. Applicability of these principles is demonstrated by employing various ditopic ligands with different bend-angles for the synthesis of a range of Pt 2 L 4 , Pt 3 L 6 , Pt 4 L 8 and Pt 12 L 24 polyhedra with platinum cornerstones in excellent yields, thus paving the way for future applications of well-defined robust platinum nanospheres of different shapes and sizes with the general composition Pt n L 2 n ., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The preparation of functionalized, heteroleptic Pd x L 2 x 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 x L 2 x 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 Pd 12 LFu 24 ( LFu = 2,5-bis(pyridyl)furan) assembly suggested the formation of a minor topology Pd 15 LFu 30 , 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 Pd 12 L 24 and Pd 24 L 48 coordination cages formation, reliably emulating experimental data. Finally, the topological outcome for exohedrally ( LEx ) and endohedrally ( LEn ) functionalized heteroleptic Pd x L 2 x 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., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

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 Pd 2+ . As these weak interactions are easily broken, the bend angles have a controlled flexibility giving access to M 2 (L1) 4 , M 6 (L2) 12 , and M 12 (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., (© 2020 Wiley-VCH GmbH.)

The cage complex [Pd294]4+ (3') binds n-octyl glycosides in DCM/DMSO (9 : 1) solution with Ka ≈ 51 M-1 for n-Oct-β-d-Glc and Ka ≈ 29 M-1 for n-Oct-β-d-Gal.

Catalysis in confined spaces, such as those provided by supramolecular cages, is quickly gaining momentum. It allows for second coordination sphere strategies to control the selectivity and activity of transition metal catalysts, beyond the classical methods like fine-tuning the steric and electronic properties of the coordinating ligands. Only a few electrocatalytic reactions within cages have been reported, and there is no information regarding the electron transfer kinetics and thermodynamics of redox-active species encapsulated into supramolecular assemblies. This contribution revolves around the preparation of M 6 L 12 and larger M 12 L 24 (M = Pd or Pt) nanospheres functionalized with different numbers of redox-active probes encapsulated within their cavity, either in a covalent fashion via different types of linkers (flexible, rigid and conjugated or rigid and nonconjugated) or by supramolecular hydrogen bonding interactions. The redox probes can be addressed by electrochemical electron transfer across the rim of nanospheres, and the thermodynamics and kinetics of this process are described. Our study identifies that the linker type and the number of redox probes within the cage are useful handles to fine-tune the electron transfer rates, paving the way for the encapsulation of electroactive catalysts and electrocatalytic applications of such supramolecular assemblies.