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The dynamic behaviour of metal‐ligand bonding cultivates stimuli‐mediated structural transformations in self‐assembled molecular architectures. The propensity of synthetically designed self‐assembled systems to interchange between higher‐order architectures is increased multi‐fold when the building blocks have higher conformational degrees of freedom. Herein, we report a new ligand, (2,7‐bis(di(pyridin‐4‐yl)amino)‐9H‐fluoren‐9‐one) (L), which, upon self‐assembly with a cis‐[(ethylene‐1,2‐diamine)Pd(NO3)2] acceptor (M), resulted in the formation of a M6L3 trifacial barrel (C1) in water. Interestingly, during crystallization, a rare M12L6 triangular orthobicupola architecture (C2) was generated along with C1. C2 could also be generated in solution via the application of several stimuli. C1 in aqueous media could stabilize one trans‐stilbene (tS) or cis‐stilbene (cS) molecule in its cavity, with a selectivity for the former from their mixture. Moreover, C1 acted as an effective host to prevent the otherwise facile photoisomerization of tS to cS inside its hydrophobic cavity under UV irradiation. Conversely, the visible‐light‐induced reverse isomerization of encapsulated cS to encapsulated tS could be achieved readily due to the better stabilization of tS within the cavity of C1 and its transparency to visible light. A multi‐functional system was therefore designed, which at the same time is stimuli‐responsive, shows isomer selectivity, and photo‐protects trans‐stilbene. [ABSTRACT FROM AUTHOR]

Nanoscale molecular materials have emerged as a new class of compounds at the nanometer scale with well‐defined chemical structures, remarkable uniformity and high reproducibility. Among these materials, zirconium‐based metal‐organic cages (MOCs) have attracted significant attention due to their exceptional stability and applications in catalysis, recognition and separation and so on. However, their poor water solubility impedes their biomedical applications. In this study, decorating the ligand with Ru(II) complexes can not only improve the water solubility but also endow bright red fluorescence with large Stokes shift (180 nm). Notably, butyl‐modification of the cyclopentadiene rings can significantly enhance the cell uptake (100 folds) of nanocages via actin‐ and dynamin‐mediated endocytosis. The unique advantages and easy modifiability of these nanocages make them highly promising candidates for diverse biological applications. [ABSTRACT FROM AUTHOR]

Complexation of Pd(II) with a designer unsymmetrical bis‐monodentate ligand (2 : 4 ratio) yielded a specific Pd2L4 type “single‐cavity discrete coordination cage” (SCDCC), from a pool of 4 isomeric structures. The observed selctivity is attributed to inherent orientational preference of the ligand strands around the metal centers. Crafting a short coordinating arm at either ends of the bis‐monodentate ligand (i.e the longer‐arm) produced a pair of unsymmetrical isomeric tris‐monodentate ligands; whereas crafting the same short‐arm at both ends of the ligand gives an unsymmetrical tetrakis‐monodentate ligand. Complexation of Pd(II) with either of the isomeric tris‐monodenate ligands (3 : 4 ratio) resulted in corresponding low‐symmetry “multi‐cavity discrete coordination cage” MCDCC having two conjoined cavities, though the inherent relative orientational preference of the longer arms is not achievable in these cages. The enforced orientation is sustained by “Neighbouring Cage Participation” (NCP). However, one‐pot combination of Pd(II), with a mixture of isomeric tris‐monodentate ligands in 3 : 2 : 2 ratio produced an integratively self‐sorted mixed‐ligated MCDCC from a pool of 31 structures. Also, mixing Pd(II) with the tetrakis‐monodentate ligand produced a MCDCC having three conjoined cavities. The inherent orientational preference of longer‐arm of the ligand strands is retained in the mixed‐ligated double‐cavity and the homo‐ligated triple cavity cages. [ABSTRACT FROM AUTHOR]

Pd(II)‐based low‐symmetry coordination cages possessing anisotropic cavities are of great interest. The common strategies employed to achieve such cages utilize either more than one type of symmetrical ligands (e.g., Laa, Lbb etc.) or only one type of unsymmetrical ligand (e.g., Lab). To significantly enhance the anisotropy, we have designed two unsymmetrical bidentate ligands i.e., Lab and Lcd, aiming at a low‐symmetry Pd2Lab2Lcd2‐type cage. It was accomplished by high‐fidelity integrative self‐sorting of two different low‐symmetry cages having Pd2Lab4 and Pd4Lcd8‐type architectures (homoleptic complexes of the designed ligands). Structural constraints and geometry complementarity in the ligand design drive the non‐statistical exclusive self‐assembly of the Pd2Lab2Lcd2‐type cage. By taking advantage of the complemental geometries between ligands, a low‐symmetry Pd2Lab2Lcc2‐type cage was also obtained. Heteromeric completive self‐sorting of three homoleptic assemblies (Pd2Lab4, Pd4Lcc8 and Pd4Lcd8‐type cages) into an exclusive mixture of Pd2Lab2Lcd2 and Pd2Lab2Lcc2‐type mixed ligated assemblies was demonstrated through cage‐to‐cage transformations. [ABSTRACT FROM AUTHOR]

The crystalline sponge method has proven invaluable in the preparation and analysis of supramolecular host/guest complexes if the host can be obtained in a suitable crystalline form, allowing the analysis of guest binding modes inside host cavities which can inform other studies into processes such as catalysis. Here, we report the structures of a set of ten host/guest complexes using an octanuclear coordination cage host with a range of small-molecule neutral organic guests including four aromatic aldehydes and ketones, three cyclic lactams, and three epoxides. In all cases, the cavity-bound guests are anchored by a collection of CH•••O hydrogen-bonding interactions between an O atom on the guest and a convergent set of CH protons at a pocket on the cage interior surface. Depending on guest size and the presence of solvent molecules as additional guests, there may be one or two cavity-bound guests, with small aromatic guests forming π-stacked pairs. Some guests (the lactams) participate in additional NH•••F H-bonding interactions with surface-bound fluoroborate anions, which indicate the type of anion/guest interactions thought to be responsible for solution-phase catalytic reactions of bound guests. [ABSTRACT FROM AUTHOR]

Polyradical cages are of great interest because they show very fascinating physical and chemical properties, but many challenges remain, especially for their synthesis and characterization. Herein, we present the synthesis of a polyradical cation cage 14⋅+ through post‐synthetic oxidation of a redox‐active phenothiazine‐based Pd2L4‐type coordination cage 1. It′s worth noting that 1 exhibits excellent reversible electrochemical and chemical redox activity due to the introduction of a bulky 3,5‐di‐tert‐butyl‐4‐methoxyphenyl substituent. The generation of 14⋅+ through reversible electrochemical oxidation is investigated by in situ UV/Vis‐NIR and EPR spectroelectrochemistry. Meanwhile, chemical oxidation of 1 can also produce 14⋅+ which can be reversibly reduced back to the original cage 1, and the process is monitored by EPR and NMR spectroscopies. Eventually, we succeed in the isolation and single crystal X‐ray diffraction analysis of 14⋅+, whose electronic structure and conformation are distinct to original 1. The magnetic susceptibility measurements indicate the predominantly antiferromagnetic interactions between the four phenothiazine radical cations in 14⋅+. We believe that our study including the facile synthesis methodology and in situ spectroelectrochemistry will shed some light on the synthesis and characterization of novel polyradical systems, opening more perspectives for developing functional supramolecular cages. [ABSTRACT FROM AUTHOR]

1,2,4-Oxadiazole based unsymmetric bidentate ligand, 3,5-bis-(4-pyridyl)-1,2,4-oxadiazole has been employed for complexation with silver nitrate; this ligand has been used for the first time for preparation of any coordination complex. A polymeric array of one-dimensional silver-ligand complex is formed where each metal ion is coordinated to two 4-pyridyl groups of two different ligands and two O-atoms of a nitrate ion. Single crystal X-ray data shows presence of hydrogen bonding and π–π stacking between each one-dimensional array which leads to formation of channels in its solid state. The hydrogen bonding interactions have also been verified by Hirsfeld surface analysis plots. Antimicrobial property study of ligand 3,5-bis-(4-pyridyl)-1,2,4-oxadiazole has been performed with Lactobacillus plantarum and it inhibits the growth at 12.5 μg/mL. [ABSTRACT FROM AUTHOR]

Controlling supramolecular systems between different functional forms by utilizing acids/bases as stimuli is a formidable challenge, especially where labile coordination bonds are involved. A pair of acid/base responsive, interconvertible 1,5‐enedione/pyrylium based Pd2L4‐type cages are prepared that exhibit differential guest binding abilities towards disulfonates of varied sizes. A three‐state switch has been achieved, where (i) a weakly coordinating base induced cage‐to‐cage transformation in the first step, (ii) a strongly coordinating base triggered cage disassembly as the second step, and (iii) the third step shows acid(strong) promoted generation of initial cage, thereby completing the cycle. To our surprise, binding of a specific disulfonate guest facilitated cage‐to‐cage transformations by inducing strain on the cage assembly thereby opening the labile pyrylium rings of the cage. Through a competitive guest binding study, we demonstrated the superior guest binding capability of the octacationic pyrylium‐based cage over a similar‐sized tetracationic cage. These results provide a reliable approach to reversibly modulate the guest binding properties of acid/base‐responsive self‐assembled coordination cages. [ABSTRACT FROM AUTHOR]

Coordination cages sustained by metal–ligand interactions feature polyhedral architectures and well-defined hollow structures, which have attracted significant attention in recent years due to a variety of structure-guided promising applications. Sulfonylcalix[4]arenes-based coordination cages, termed metal–organic supercontainers (MOSCs), that possess unique multi-pore architectures containing an endo cavity and multiple exo cavities, are emerging as a new family of coordination cages. The well-defined built-in multiple binding domains of MOSCs allow the efficient encapsulation of guest molecules, especially for drug delivery. Here, we critically discuss the design strategy, and, most importantly, the recent advances in research surrounding cavity-specified host–guest chemistry and biomedical applications of MOSCs. [ABSTRACT FROM AUTHOR]

The crystalline sponge method has proven invaluable in the preparation and analysis of supramolecular host/guest complexes if the host can be obtained in a suitable crystalline form, allowing the analysis of guest binding modes inside host cavities which can inform other studies into processes such as catalysis. Here, we report the structures of a set of ten host/guest complexes using an octanuclear coordination cage host with a range of small-molecule neutral organic guests including four aromatic aldehydes and ketones, three cyclic lactams, and three epoxides. In all cases, the cavity-bound guests are anchored by a collection of CH•••O hydrogen-bonding interactions between an O atom on the guest and a convergent set of CH protons at a pocket on the cage interior surface. Depending on guest size and the presence of solvent molecules as additional guests, there may be one or two cavity-bound guests, with small aromatic guests forming π-stacked pairs. Some guests (the lactams) participate in additional NH•••F H-bonding interactions with surface-bound fluoroborate anions, which indicate the type of anion/guest interactions thought to be responsible for solution-phase catalytic reactions of bound guests.

Metal‐organic cages (MOCs) are popular host architectures assembled from ligands and metal ions/nodes. Assembling structurally complex, low‐symmetry MOCs with anisotropic cavities can be limited by the formation of statistical isomer libraries. We set out to investigate the use of primary coordination‐sphere engineering (CSE) to bias isomer selectivity within homo‐ and heteroleptic PdnL2n cages. Unexpected differences in selectivities between alternative donor groups led us to recognise the significant impact of the second coordination sphere on isomer stabilities. From this, molecular‐level insight into the origins of selectivity between cis and trans diastereoisomers was gained, highlighting the importance of both host–guest and host‐solvent interactions, in addition to ligand design. This detailed understanding allows precision engineering of low‐symmetry MOC assemblies without wholesale redesign of the ligand framework, and fundamentally provides a theoretical scaffold for the development of stimuli‐responsive, shape‐shifting MOCs. [ABSTRACT FROM AUTHOR]

A strategy to engineer the stacking of diketopyrrolopyrrole (DPP) dyes based on non‐statistical metallosupramolecular self‐assembly is introduced. For this, the DPP backbone is equipped with nitrogen‐based donors that allow for different discrete assemblies to be formed upon the addition of Pd(II), distinguished by the number of π‐stacked chromophores. A Pd3L6 three‐ring, a heteroleptic Pd2L2L′2 ravel composed of two crossing DPPs (flanked by two carbazoles), and two unprecedented self‐penetrated motifs (a Pd2L3 triple and a Pd2L4 quadruple stack), were obtained and systematically investigated. With increasing counts of stacked chromophores, UV/Vis absorptions red‐shift and emission intensities decrease, except for compound Pd2L2L′2, which stands out with an exceptional photoluminescence quantum yield of 51 %. This is extraordinary for open‐shell metal containing assemblies and explainable by an intra‐assembly FRET process. The modular design and synthesis of soluble multi‐chromophore building blocks offers the potential for the preparation of nanodevices and materials with applications in sensing, photo‐redox catalysis and optics. [ABSTRACT FROM AUTHOR]

Numerous indole alkaloids such as the iboga‐ and aspidosperma‐type are believed to be biosynthesized via a common hypothetical intermediate, dehydrosecodine. The highly reactive nature of dehydrosecodine‐type compounds has hampered their isolation and structural elucidation. In this study, we achieved the first X‐ray structural determination of a dehydrosecodine‐type compound by integrating synthetic optimization of the reactivity and stabilizing the fragile molecule by encapsulation into a supramolecular host. Formation of a 1 : 1 complex of the dehydrosecodine‐type labile guest bearing both vinyl indole and dihydropyridine units with the host was observed. This integrated approach not only provides insights into the biosynthetic conversions but also allows stabilization and storage of the reactive and otherwise short‐lived intermediate within the confined hydrophobic cavity. [ABSTRACT FROM AUTHOR]

Coordination cages can be used for enantio‐ and regioselective catalysis and for the selective sensing and separation of isomeric guest molecules. Here, stereoisomers of a family of coordination cages are resolved using ultra‐high‐resolution cyclic ion‐mobility mass spectrometry (cIM‐MS). The observed ratio of diastereomers is dependent on both the metal ion and counter ion. Moreover, the point groups can be assigned through complementary NMR experiments. This method enables the identification and interrogation of the individual isomers in complex mixtures of cages which cannot be performed in solution. Furthermore, these techniques allow the stability of individual isomers within the mixture to be probed, with the T‐symmetric isomers in this case shown to be more robust than the C3 and S4 analogues. [ABSTRACT FROM AUTHOR]

Coordination cages with intrinsic enzyme-like activity are a class of promising catalysts for improving the efficiency of organic reactions. We present herein a viable strategy to conveniently construct multimetallic active sites into a coordination cage via self-assembly of a pre-formed sulfonylcalix[4]arene-based tetranuclear copper(II) precursor and an amino-functionalized dicarboxylate linker. The cage exhibits a "defective", partially open cylindrical structure and features coordinatively labile dimetallic Cu(II) sites. Modulated by this unique inner cavity environment, promising catalytic activity toward selective oxidation of primary alcohols to carboxylic acids at room temperature is achieved. Mechanistic studies reveal that the coordinatively labile dimetallic Cu(II) sites can efficiently capture and activate the substrate and oxidant to catalyze the reaction, while the confined nano-cavity environment modulates substrate binding and enhances the catalytic turnover. This study provides a new approach to designing biomimetic multifunctional coordination cages and environmentally friendly supramolecular catalysts. [ABSTRACT FROM AUTHOR]

Coordination cages sustained by metal–ligand interactions feature polyhedral architectures and well-defined hollow structures, which have attracted significant attention in recent years due to a variety of structure-guided promising applications. Sulfonylcalix[4]arenes-based coordination cages, termed metal–organic supercontainers (MOSCs), that possess unique multi-pore architectures containing an endo cavity and multiple exo cavities, are emerging as a new family of coordination cages. The well-defined built-in multiple binding domains of MOSCs allow the efficient encapsulation of guest molecules, especially for drug delivery. Here, we critically discuss the design strategy, and, most importantly, the recent advances in research surrounding cavity-specified host–guest chemistry and biomedical applications of MOSCs.

Amino acids provide a convenient, economical, and non-toxic route for the synthesis of chiral metallosupramolecular architectures, including coordination cages and metal–organic cages, metallocycles, and metallocatenanes. In this review, we collate recent works on supramolecular coordination complexes assembled with amino acid derivatives, while highlighting the role of the amino acid on the chirality, coordination chemistry, and supramolecular chemistry of these complexes. [Display omitted] • Amino acids are cheap but versatile sources of chirality in supramolecular systems. • Monodentate, bridging and chelating modes are possible with amino acid derivatives. • Amino acids have been used to assemble chiral metallocycles, catenanes and cages. • Often, amino acids are incorporated into ligands with amide, imide or imine groups. • Amino acids steer stereoselective self-assembly and provide hydrogen-bonding sites. [ABSTRACT FROM AUTHOR]

Metallosupramolecular hosts of nanoscopic dimensions, which are able to serve as selective receptors and catalysts, are usually composed of only one type of organic ligand, restricting diversity in terms of cavity shape and functional group decoration. We report a series of heteroleptic [Pd2A2B2] coordination cages that self‐assemble from a library of shape complementary bis‐monodentate ligands in a non‐statistical fashion. Ligands A feature an inward pointing NH function, able to engage in hydrogen bonding and amenable to being functionalized with amide and alkyl substituents. Ligands B comprise tricyclic aromatic backbones of different shape and electronic situation. The obtained heteroleptic coordination cages were investigated for their ability to bind phosphate diesters as guests. All‐atom molecular dynamics (MD) simulations in explicit solvent were conducted to understand the mechanistic relationships behind the experimentally determined guest affinities. [ABSTRACT FROM AUTHOR]

The dynamic behaviour of metal-ligand bonding cultivates stimuli-mediated structural transformations in self-assembled molecular architectures. The propensity of synthetically designed self-assembled systems to interchange between higher-order architectures is increased multi-fold when the building blocks have higher conformational degrees of freedom. Herein, we report a new ligand, (2,7-bis(di(pyridin-4-yl)amino)-9H-fluoren-9-one) (L), which, upon self-assembly with a cis-[(ethylene-1,2-diamine)Pd(NO 3 ) 2 ] acceptor (M), resulted in the formation of a M 6 L 3 trifacial barrel (C1) in water. Interestingly, during crystallization, a rare M 12 L 6 triangular orthobicupola architecture (C2) was generated along with C1. C2 could also be generated in solution via the application of several stimuli. C1 in aqueous media could stabilize one trans-stilbene (tS) or cis-stilbene (cS) molecule in its cavity, with a selectivity for the former from their mixture. Moreover, C1 acted as an effective host to prevent the otherwise facile photoisomerization of tS to cS inside its hydrophobic cavity under UV irradiation. Conversely, the visible-light-induced reverse isomerization of encapsulated cS to encapsulated tS could be achieved readily due to the better stabilization of tS within the cavity of C1 and its transparency to visible light. A multi-functional system was therefore designed, which at the same time is stimuli-responsive, shows isomer selectivity, and photo-protects trans-stilbene., (© 2024 Wiley-VCH GmbH.)

Multicomponent metallo‐supramolecular assembly allows the rational combination of different building blocks. Discrete multifunctional hosts with an accessible cavity can be prepared in a non‐statistical fashion. We employ our shape‐complementary assembly (SCA) method to achieve for the first time integrative self‐sorting of heteroleptic PdII cages showing guest‐tunable circularly polarized luminescence (CPL). An enantiopure helicene‐based ligand (M or P configuration) is coupled with a non‐chiral emissive fluorenone‐based ligand (A or B) to form a series of Pd2L2L′2 assemblies. The modular strategy allows to impart the chiral information of the helicenes to the overall supramolecular system, resulting in CPL from the non‐chiral component. Guest binding results in a 4‐fold increase of CPL intensity. The principle offers potential to generate libraries of multifunctional materials with applications in molecular recognition, enantioselective photo‐redox catalysis and information processing. [ABSTRACT FROM AUTHOR]

Controllable arrangement of different ligands in a single assembly will not only bring increased complexity but also offers a new route to fine‐tune the function of the designed architecture. We report here a combinatorial self‐assembly with enPd(NO3)2 and three different ligands (L1–3), which gave rise to a family of six palladium‐organic cages (C1‐6) with systematically varied shapes and cavities, including three new heteroleptic (Pd5L12L2, Pd5L12L3, Pd4L2L3), one new homoleptic (Pd4L32) cages, and two known homoleptic (Pd6L14, Pd4L22) cages. Emergent functions due to the fusion of two half cavities on the heteroleptic cages from their parent homoleptic cages have been observed: the heteroleptic cages can form ternary complexes by co‐encapsulation of both aromatic and aliphatic guests, while their homoleptic counterparts can only form binary complexes. Such a forced co‐encapsulation effect endows the heteroleptic cages with enhanced catalytic power for the Knoevenagel condensation. [ABSTRACT FROM AUTHOR]

• Coordination finite species based on thiacalix[4]arene macrocyclic backbones are reviewed. • The coordination abilities of calixarene based ligands towards metals are presented. • The effect of additional ligands on the nuclearity and shape of the finite species is discussed. • The useful properties of the resulting intriguing architectures are highlighted. The preparation and rational design of nanosized clusters (M n) and cages based on the macrocyclic thiacalix[4]arene backbone in cone conformation has been analysed in the presence/absence of O and N donor atoms from different additional ligands. The coordination abilities of this class of macrocyclic ligands is reviewed leading to supramolecular species like: (1) metallic (Ag, Au) core Nanoparticles decorated with an organic thiacalix[4]arene derivatives shell; (2) different types of high nuclearity clusters (up to M 32); (3) metallamacrocycles (up to M 30); (4) pocket-like (M 6 or M 8) or square-like species (M 16) presenting internal and external porosity (5) octahedral cages involving 8 or 12 external ligands paving the faces or edges of the octahedron (6) species of higher nuclearity (up to M 72). For the pocket-like, square-like and octahedral species, their formation has been rationalized by the use of judiciously chosen organic ligands, as shown by the systematic analysis. A special attention has been drawn to the structure/properties relationships of these finite species: magnetic, luminescence, gas sorption, molecular recognition and catalytic properties. Perspectives and future challenges in this emerging field are also discussed. [ABSTRACT FROM AUTHOR]

Nonaqueous emulsions are crucial for a range of applications based on water‐sensitive systems such as controlled polymerizations requiring anhydrous reaction conditions and the stabilization of readily hydrolyzable reagents or pharmacologically active components. However, defined molecular surfactants to stabilize such nonaqueous emulsions are scarce. We introduce a self‐assembled coordination cage, decorated with cholesterol functionalities, to serve as a molecular surfactant for various oil‐in‐oil emulsions of immiscible organic solvents. While the positively charged cage forms the amphiphile's polar moiety, the non‐polar cholesterol appendices can bend in a common direction to stabilize the emulsion. Templated by the droplets, polycondensation reactions were carried out to produce microstructured polyurethane and polyurea materials of different particle sizes and morphologies. Further, the amphiphilic cage can encapsulate a guest molecule and the resulting host‐guest assembly was also examined as a surfactant. In addition, the aggregation behavior of the amphiphilic cage in an aqueous medium was examined. [ABSTRACT FROM AUTHOR]

Pd(II)-based low-symmetry coordination cages possessing anisotropic cavities are of great interest. The common strategies employed to achieve such cages utilize either more than one type of symmetrical ligands (e.g., L aa , L bb etc.) or only one type of unsymmetrical ligand (e.g., L ab ). To significantly enhance the anisotropy, we have designed two unsymmetrical bidentate ligands i.e., L ab and L cd , aiming at a low-symmetry Pd 2 L ab 2 L cd 2 -type cage. It was accomplished by high-fidelity integrative self-sorting of two different low-symmetry cages having Pd 2 L ab 4 and Pd 4 L cd 8 -type architectures (homoleptic complexes of the designed ligands). Structural constraints and geometry complementarity in the ligand design drive the non-statistical exclusive self-assembly of the Pd 2 L ab 2 L cd 2 -type cage. By taking advantage of the complemental geometries between ligands, a low-symmetry Pd 2 L ab 2 L cc 2 -type cage was also obtained. Heteromeric completive self-sorting of three homoleptic assemblies (Pd 2 L ab 4 , Pd 4 L cc 8 and Pd 4 L cd 8 -type cages) into an exclusive mixture of Pd 2 L ab 2 L cd 2 and Pd 2 L ab 2 L cc 2 -type mixed ligated assemblies was demonstrated through cage-to-cage transformations., (© 2024 Wiley-VCH GmbH.)

Polyradical cages are of great interest because they show very fascinating physical and chemical properties, but many challenges remain, especially for their synthesis and characterization. Herein, we present the synthesis of a polyradical cation cage 1 4 ⋅ + through post-synthetic oxidation of a redox-active phenothiazine-based Pd 2 L 4 -type coordination cage 1. It's worth noting that 1 exhibits excellent reversible electrochemical and chemical redox activity due to the introduction of a bulky 3,5-di-tert-butyl-4-methoxyphenyl substituent. The generation of 1 4 ⋅ + through reversible electrochemical oxidation is investigated by in situ UV/Vis-NIR and EPR spectroelectrochemistry. Meanwhile, chemical oxidation of 1 can also produce 1 4 ⋅ + which can be reversibly reduced back to the original cage 1, and the process is monitored by EPR and NMR spectroscopies. Eventually, we succeed in the isolation and single crystal X-ray diffraction analysis of 1 4 ⋅ + , whose electronic structure and conformation are distinct to original 1. The magnetic susceptibility measurements indicate the predominantly antiferromagnetic interactions between the four phenothiazine radical cations in 1 4 ⋅ + . We believe that our study including the facile synthesis methodology and in situ spectroelectrochemistry will shed some light on the synthesis and characterization of novel polyradical systems, opening more perspectives for developing functional supramolecular cages., (© 2024 Wiley-VCH GmbH.)

Metallo‐supramolecular self‐assembly has yielded a plethora of discrete nanosystems, many of which show competence in capturing guests and catalyzing chemical reactions. However, the potential of low‐molecular bottom‐up self‐assemblies in the development of structured inorganic materials has rarely been methodically explored so far. Herein, we present a new type of metallo‐supramolecular surfactant with the ability to stabilize non‐aqueous emulsions for a significant period. The molecular design of the surfactant is based on a heteroleptic coordination cage (CGA‐3; CGA=Cage‐based Gemini Amphiphile), assembled from two pairs of organic building blocks, grouped around two Pd(II) cations. Shape‐complementarity between the differently functionalized components generates discrete amphiphiles with a tailor‐made polarity profile, able to stabilize non‐aqueous emulsions, such as hexadecane‐in‐DMSO. These emulsions were used as a medium for the synthesis of spherical metal oxide microcapsules (titanium oxide, zirconium oxide, and niobium oxide) from soluble, water‐sensitive alkoxide precursors by allowing a controlled dosage of water to the liquid‐liquid phase boundary. Synthesized materials were analyzed by a combination of electron microscopic techniques. In situ liquid cell transmission electron microscopy (LC‐TEM) was utilized for the first time to visualize the dynamics of the emulsion‐templated formation of hollow inorganic titanium oxide and zirconium oxide microspheres. [ABSTRACT FROM AUTHOR]

In recent years, increasing efforts have been devoted to designing new functional stimuli-responsive supramolecular assemblies. Here, we present three isomeric supramolecular coordination complexes consisting of a Pd2L4 stoichiometry. As shown by NMR, CD and X-ray studies, as well as DFT calculations, these complexes form cage-like structures by chiral self-sorting. Photochromic ligands derived from first generation molecular motors enable light-driven interconversion between the three isomers. Two of the isomers were able to form host–guest complexes opening up new prospects toward stimuli-controlled substrate binding and release.

Arylazopyrazoles represent a new family of molecular photoswitches characterized by a near-quantitative conversion between two states and long thermal half-lives of the metastable state. Here, we investigated the behavior of a model arylazopyrazole in the presence of a self-assembled cage based on Pd–imidazole coordination. Owing to its high water solubility, the cage can solubilize the E isomer of arylazopyrazole, which, by itself, is not soluble in water. NMR spectroscopy and X-ray crystallography have independently demonstrated that each cage can encapsulate two molecules of E-arylazopyrazole. UV-induced switching to the Z isomer was accompanied by the release of one of the two guests from the cage and the formation of a 1:1 cage/Z-arylazopyrazole inclusion complex. DFT calculations suggest that this process involves a dramatic change in the conformation of the cage. Back-isomerization was induced with green light and resulted in the initial 1:2 cage/E-arylazopyrazole complex. This back-isomerization reaction also proceeded in the dark, with a rate significantly higher than in the absence of the cage.

Spherical assemblies of the type [PdnL2n]2n+ can be obtained from PdII 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 [PdnLnL′n]2n+, for which a similar correlation between the ligand bent angle and the nuclearity is observed. Tetranuclear cages were obtained by combining [Pd(CH3CN)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 [Pd8L8L′8]16+ were obtained. The predictable formation of heteroleptic PdII 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. [ABSTRACT FROM AUTHOR]

We report the synthesis of a novel metal–organic capsule constructed from six pyrogallol[4]arene macrocycles, which are switched together by 16 FeIII and 16 CoII ions. This supramolecular structure is the first instance of a spheroidal heterometallic nanocage assembled through a one‐step metal–ligand coordination approach. This new assembly also demonstrates an important proof of concept through the formation of multiple heterometallic metal–metal interactions within the capsule framework. Photophysical and electrochemical studies of self‐assembled capsule films indicate their potential as semiconductors. These materials display unexpected photoelectric conversion properties, thus representing an emergent phenomenon in discrete metal–organic supramolecular assemblies. [ABSTRACT FROM AUTHOR]

The combination of shape‐complementary bis‐monodentate ligands LA and LB with PdII cations yields heteroleptic cages cis‐[Pd2LA2LB2] by self‐sorting. Herein, we report how such assemblies can be diversified by introduction of covalent backbone bridges between two LA units. Together with solvent and guest effects, the flexibility of these linkers can modulate nuclearity, topology, and number of cavities in a family of four structurally diverse assemblies. Ligand LA1, with flexible linker, reacts in CH3CN with its LB counterpart to a tetranuclear dimer D1. In DMSO, however, a trinuclear pseudo‐tetrahedron T1 is formed. The product of LA2, with rigid linker, looks similar to D1, but with a rotated ligand arrangement. In presence of an anionic guest, this dimer D2 transforms and a hexanuclear prismatic barrel P2 crystallizes. We demonstrate how controlling a ligand's coordination mode can trigger structural differentiation and increase complexity in metallo‐supramolecular assembly. [ABSTRACT FROM AUTHOR]

A strategy to implement four members of the classic coal‐tar dye family, Michler's ketone, methylene blue, rhodamine B, and crystal violet, into [Pd2L4] self‐assemblies is introduced. Chromophores were incorporated into bis‐monodentate ligands using piperazine linkers that allow to retain the auxochromic dialkyl amine functionalities required for intense colors deep in the visible spectrum. Upon palladium coordination, ligands with pyridine donors form lantern‐shaped dinuclear cages while quinoline donors lead to strongly twisted [Pd2L4] helicates in solution. In one case, single crystal X‐ray diffraction revealed rearrangement to a [Pd3L6] ring structure in the solid state. For nine examined derivatives, showing colors from yellow to deep violet, CD spectroscopy discloses different degrees of chiral induction by an enantiomerically pure guest. Ion mobility mass spectrometry allows to distinguish two binding modes. Self‐assemblies based on this new ligand class promise application in chiroptical recognition, photo‐redox catalysis and optical materials. [ABSTRACT FROM AUTHOR]

Molecules with permanent porosity in the solid state have been studied for decades. Porosity in these systems is governed by intrinsic pore space, as in cages or macrocycles, and extrinsic void space, created through loose, intermolecular solid‐state packing. The development of permanently porous molecular materials, especially cages with organic or metal–organic composition, has seen increased interest over the past decade, and as such, incredibly high surface areas have been reported for these solids. Despite this, examples of these materials being explored for gas storage applications are relatively limited. This minireview outlines existing molecular systems that have been investigated for gas storage and highlights strategies that have been used to understand adsorption mechanisms in porous molecular materials. [ABSTRACT FROM AUTHOR]

The self‐assembly of highly stable zirconium(IV)‐based coordination cages with aggregation induced emission (AIE) molecular rotors for in vitro bio‐imaging is reported. The two coordination cages, NUS‐100 and NUS‐101, are assembled from the highly stable trinuclear zirconium vertices and two flexible carboxyl‐decorated tetraphenylethylene (TPE) spacers. Extensive experimental and theoretical results show that the emissive intensity of the coordination cages can be controlled by restricting the dynamics of AIE‐active molecular rotors though multiple external stimuli. Because the two coordination cages have excellent chemical stability in aqueous solutions (pH stability: 2–10) and impressive AIE characteristics contributed by the molecular rotors, they can be employed as novel biological fluorescent probes for in vitro live‐cell imaging. [ABSTRACT FROM AUTHOR]

The ability to control structure and function of metal-organic cages by external stimuli offers many possibilities. For example, preventing product inhibition in catalysis, releasing a drug at a specific site, or altering material properties. This Highlight Review describes the different strategies that have been developed to make light-responsive metal-organic cages able to undergo a structural change in response to a light stimulus and furthermore, major challenges and future perspectives are discussed. [ABSTRACT FROM AUTHOR]

A hexameric metal–organic nanocapsule is assembled from pyrogallol[4]arene units, which are stitched together with indium ions. This indium‐seamed capsule is the first instance of a M24L6 type hexameric coordination cage held together exclusively by trivalent metal ions. Explicitly, unlike previously reported pyrogallol[4]arene‐based metal‐seamed capsules, the current In3+ seamed capsule is entirely supported by O→In coordinate bonds. This work demonstrates the important proof of concept of the ability of pyrogallol[4]arene to react with metals in higher oxidation states to assemble into atomically‐precise hexameric coordination cages. As such, these results open up exciting avenues toward the assembly of previously unanticipated metal–organic capsules, for example offering inspiration for tackling metals exhibiting high valence states such as in the lanthanide and actinide series. [ABSTRACT FROM AUTHOR]

This work demonstrates a new nonconventional ligand design, imidazole/pyridine‐based nonsymmetrical ditopic ligands (1 and 1S), to construct a dynamic open coordination cage from nonsymmetrical building blocks. Upon complex formation with Pd2+ at a 1:4 molar ratio, 1 and 1S initially form mononuclear PdL4 complexes (Pd2+(1)4 and Pd2+(1S)4) without formation of a cage. The PdL4 complexes undergo a stoichiometrically controlled structural transition to Pd2L4 open cages ((Pd2+)2(1)4 and (Pd2+)2(1S)4) capable of anion binding, leading to turn‐on anion binding. The structural transitions between the Pd2L4 open cage and the PdL4 complex are reversible. Thus, stoichiometric addition (2 equiv) of free 1S to the (Pd2+)2(1S)4 open cage holding a guest anion ((Pd2+)2(1S)4⋅G−) enables the structural transition to the Pd2+(1S)4 complex, which does not have a cage and thus causes the release of the guest anion (Pd2+(1S)4+G−). [ABSTRACT FROM AUTHOR]

For metal‐mediated host compounds, the development of strategies to reduce symmetry and introduce multiple functionalities in a non‐statistical way is a challenging task. We show that the introduction of steric stress around the coordination environment of square‐planar PdII cations and bis‐monodentate nitrogen donor ligands allows to control the size and shape of the assembled product, from [Pd2L4] cages over [Pd2L3] bowl‐shaped structures to [Pd2L2] rings. Therefore, banana‐shaped ligand backbones were equipped with pyridines, two different quinoline isomers and acridine, the latter three introducing steric congestion through hydrogen substituents on annelated benzene rings. Differing behavior of the four resulting hosts towards the binding of C60 and C70 fullerenes was studied and related to structural differences by NMR spectroscopy, mass spectrometry and single crystal X‐ray diffraction. The three cages based on pyridine, 6‐quinoline or 3‐quinoline donors were found to either bind C60, C70 or no fullerene at all. [ABSTRACT FROM AUTHOR]

Metallosupramolecular assemblies of the general formula M2nLn can adopt prismatic or cage‐like structures. The factors controlling the aggregation number n and the geometry of the final assembly are still not fully understood. Here, we describe the synthesis and the structural characterization of PtII8L4 complexes, which adopt tetragonal prismatic structures. The bridging ligand L features four pyridyl groups and an inert FeII clathrochelate complex at its core. Furthermore, the ligand has three phenanthrene groups, which are attached to the FeII complex in a divergent fashion. These polyaromatic side groups control the self‐assembly process by promoting the formation of a structure, which allows for an energetically favorable packing of the aromatic groups. Replacing the phenanthrene groups on the ligand by aliphatic n‐butyl groups results in a complete change of geometry: instead of tetragonal prisms, PtII8L4 complexes with cage‐like structures are observed. [ABSTRACT FROM AUTHOR]

A new series of [Pd2(L)4] cages based on photochromic dithienylethene (DTE) ligands allowed us to gain insight into the successive photoswitching of multiple DTE moieties in a confined metallo‐supramolecular assembly. Three new X‐ray structures of [Pd2(o‐L4)4], [Pd2(o‐L1)2(c‐L1)2] and [Pd2(c‐L1)4] (o‐L and c‐L = open and closed forms of DTE ligands, respectively) were obtained. The structures deliver snapshots of three different combinations of DTE photoisomeric states within the cage, facilitating a comparison of the all‐open with the all‐closed, and most notably, an intermediate form where open and closed switches co‐exist in the same cage. Moreover, a series of spherical anionic borate clusters was introduced in order to study their roles in the light‐controllable host–guest chemistry. The binding guests show higher affinities with the flexible open cage [Pd2(o‐L1)4] than with the rigid closed cage [Pd2(c‐L1)4]. For the [B12F12]2− guest, thermodynamic data obtained from NMR experiments was compared to results from isothermal titration calorimetry (ITC). [ABSTRACT FROM AUTHOR]

Porous molecular cages have a characteristic processability arising from their solubility, which allows their incorporation into porous materials. Attaining solubility often requires covalently bound functional groups that are unnecessary for porosity and which ultimately occupy free volume in the materials, decreasing their surface areas. Here, a method is described that takes advantage of the coordination bonds in metal–organic polyhedra (MOPs) to render insoluble MOPs soluble by reversibly attaching an alkyl‐functionalized ligand. We then use the newly soluble MOPs as monomers for supramolecular polymerization reactions, obtaining permanently porous, amorphous polymers with the shape of colloids and gels, which display increased gas uptake in comparison with materials made with covalently functionalized MOPs. [ABSTRACT FROM AUTHOR]