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Herein, we have successfully achieved the stereoselective synthesis of two chiral radial [5]catenanes in a single step through the self-assembly of bidentate ligands containing l-alanine residues and binuclear half-sandwich organometallic rhodium(III)/iridium(III) clips. Remarkably, these two chiral radial [5]catenanes exhibit complex stereochemical structures as revealed by single-crystal X-ray diffraction. The eight binuclear units and eight bidentate ligands in their solid-state structures all exhibit a single planar chirality, and the interlocking between molecular macrocycles exhibits a single co-conformational mechanical helical chirality. This indicates that the introduction of the point chirality in the ligands enables the efficient stereoselective construction of mechanically interlocked molecules. Furthermore, by using ligands containing d-alanine residues, radial [5]catenanes with the opposite planar chirality and opposite co-conformational mechanical helical chirality have also been obtained.

A Cp*-Rh based D-shaped binuclear metallacycle and a template-free molecular Borromean ring (BR) were obtained in high yield using the semi-rigid thioether dipyridyl ligand 1,4-bis[(pyridin-4-ylthio)methyl]benzene (Bptmb). The topological transformation from a binuclear metallacycle and a BR to tetranuclear metallacycles was realized via the controlled oxidation of thioethers. The strategy used in this work can be regarded as a new form of stimuli-responsive post-synthesis modification (PSM).

The controllable B-H bond activation of carboranes has long been a compelling challenge. However, as the symmetry of para-carborane places the same charge on all of its ten boron atoms, controlling the regiochemistry of B-H bond activation in these molecules has remained out of reach ever since their discovery. Herein, we describe how to use steric effects to achieve a regioselective process for B-H activation of para-carborane. In this strategy, B(2,8)-H or B(2,7)-H activation patterns were achieved by taking advantage of the π-π interactions between pyridine ligands. Interestingly, by employing host-guest interactions in metallacage compounds, B(2,8)-H bond activation could be avoided and exclusive B(2,9)-H bond activation can be achieved. Steric hindrance was also found to be beneficial for regioselective B(2,8)-H bond activation in metallacage species. In this work, we demonstrate that steric effects can be a promising driving force for controllable activation of the B-H bonds of carboranes and open new opportunities in this field.

Two molecular metalla-knots containing over 500 non-hydrogen atoms (especially 16 RhIII ions) and one molecular Borromean ring were obtained in high yields facilitated by multiple intermolecular interactions between their components. The syntheses rely on the strategic selection of the nonlinear dipyridyl ligand 2,7-di(pyridin-4-yl)-9H-fluorene (L1) as precursor, and the structures of the assemblies were confirmed by detailed X-ray crystallographic analysis. Subsequently, replacing L1 with the bulkier ligand 4,4'-(9,9-dimethyl-9H-fluorene-2,7-diyl)dipyridine (L2) led to the formation of three tetranuclear metallocycles in high yields on account of the weakened π-π stacking interactions between the naphthacene/anthracene and fluorene moieties, which in turn confirmed the significance of stacking interactions in the construction of the molecular 818 metalla-knots and the molecular Borromean ring.

Molecular figure-eight knot (notation: 41) is extremely rare and presents great synthetic challenge due to its essentially complicated entanglement. To solve this synthetic problem, a quadruple sta...

Herein, we describe how to utilize dihydrogen bond interactions to achieve alkane recognition and hexane isomer separation. A series of metallacycles based on carborane backbones are presented herein, revealing interdependent B-Hδ-···Hδ+-C proton-hydride interactions. The metallacycles take advantage of these dihydrogen bond interactions for the separation of hexane isomers. We show that the metallacycle 3a, bearing 1,4-di(4-pyridyl)benzene (DPB), can produce n-hexane with a purity of >99% in a single adsorption-desorption cycle from an equimolar mixture of all five isomers of hexane. The isomers 2-methylpentane and 3-methylpentane can be selectively absorbed by metallacycle 4a, which bears 1,2-di(4-pyridyl)ethylene (DPE). The size of the metallacycle, C-H···π interactions, and particularly B-Hδ-···Hδ+-C interactions are the main forces governing the extent of hexane recognition. This work provides a promising principle for the design of supramolecular coordination complexes (SCCs) for the separation of alkanes.

Separation of light hydrocarbons (C

We report a design strategy for integrative assembly of heteromeric [2]catenanes. The design focuses on the shape and functional group match of two different metalla-rectangles. A series of dipyridyl ligands with different lengths, widths and functional groups were designed and used for assembly experiments. Six heteromeric [2]catenanes were obtained both by direct mixture of two pre-assembled metalla-rectangles and one-pot three-component self-assembly. Multiple analytic methods were employed to characterize the catenanes, including single crystal X-ray diffraction analysis, NMR spectroscopy, mass spectroscopy and elemental analysis.

Although a large number of novel supramolecular topologies featuring half-sandwich [Cp*Rh] units have been reported, investigations into the properties of these architectures are astoundingly rare. In addition, the bidentate ligands employed to prepare these species have remained relatively homogeneous (i.e., symmetrical bis(pyri-4-dyl) ligands). To address these paucities in the field, the novel unsymmetrical ligand L2 and the rarely reported pyri-3-dyl ligand L3, all bearing aromatic phenazine groups (an N-heterocyclic analog of anthracene), were synthesized in addition to the common symmetrical pyri-4-dyl L1. [3]Catenane, [2]catenane, and Borromean rings assemblies were constructed successfully by the self-assembly of L1 with different building blocks. Afterward, ligand L2 was applied to prepare two novel molecular-tweezer-like compounds. Lastly, a twisted [2]catenane (relative to the [2]catenane constructed using L1) and a sandwiched metallarectangle were obtained using L3. π-π stacking interactions were observed to play a significant role in stabilizing these topologies, which also promoted nonradiative migration and triggered photothermal conversion in both the solution and the solid state. In the solution state, a clear rule of thumb was derived whereby the NIR photothermal conversion efficiency increased as the π-π stacking increased, and a very high photothermal conversion efficiency (35.5-62.4%) was observed. In addition, this family of half-sandwich-based assemblies also exhibited good photothermal conversion properties in the crystalline and noncrystal powder states. This research provides a novel method to synthesize excellent NIR photothermal conversion materials featuring half-sandwich [Cp*Rh] units and points to potential applications in the near future.

The formation of two types of heterobimetallic molecular knots, double trefoil and trefoil knots, induced by s-block metal ions, is presented. Coordination of K+, Ca2+, Sr2+ or Ba2+ ions with amide groups plays a crucial role in the formation of these trefoil knots. Remarkably, the reversible topological transformation between a figure-eight knot and double trefoil or trefoil knots can be induced by coordination of s-block metal ions to amide groups. X-ray crystallographic data and NMR experiments support the structural assignments.

Herein, we report a hierarchical assembly strategy for constructing heterogeneous half-sandwich organometallic D–A (D = π-donor, A = π-acceptor) interlocked structures, and their application in near-infrared (NIR) photothermal conversion. Thienothiophene and diketopyrrolopyrrole groups were selected as the D and A units, leading to two homogeneous metalla[2]catenanes with D–D–D–D and A–A–A–A stacks, respectively. By the ordered secondary assembly of homogeneous metalla[2]catenanes, two unprecedented heterogeneous D–A metalla[2]catenanes comprising an unusual mixed D–A–D–D and unconventional D–A–A–A stacks were realized by the combination of multiple noncovalent interactions, as all demonstrated by a detailed X-ray crystallographic study. Benefiting from the mixed D–A stacking modes, NIR absorption of heterogeneous D–A metalla[2]catenanes is significantly enhanced in contrast to homogeneous metalla[2]catenanes. Thanks to the enhanced NIR absorption and the fluorescence quenching effect from half-sandwich organometallic fragments, heterogeneous D–A metalla[2]catenanes displayed high-performance NIR photothermal conversion properties (η = 27.3%)., Herein, we report a hierarchical assembly strategy for constructing heterogeneous half-sandwich organometallic D–A (D = π-donor, A = π-acceptor) interlocked structures, and their application in near-infrared (NIR) photothermal conversion.

The synthesis of complicated supramolecular architectures and the study of their reversible structural transformations remains a fascinating challenge in the field of supramolecular chemistry. Herein, two types of novel coordination compounds, a non-intertwined ring-in-ring assembly and an abnormal trefoil knot were constructed from a strategically selected Cp*Rh building block and a semi-rigid N,N′-bis(4-pyridylmethyl)diphthalic diimide ligand via coordination-driven self-assembly. Remarkably, the reversible transformation between the abnormal trefoil knot and the ring-in-ring assembly or the corresponding tetranuclear macrocycle could be achieved by the synergistic effects of Ag+ ion coordination and alteration of the solvent. Single-crystal X-ray crystallographic data and NMR spectroscopic experiments support the structural assignments., The chemical reactivity of Ag+ ions and solvent effects induce reversible structural transformations between an abnormal trefoil knot, a tetranuclear macrocycle and a ring-in-ring architecture.

By taking advantage of self-complementary π-π stacking and CH-π interactions, a series of discrete quadruple stacks were constructed through the self-aggregation of U-shaped dirhodium metallotweezer complexes featuring various planar polyaromatic ligands. By altering the conjugate stacking strength and bridging ligands, assemblies with a range of topologies were obtained, including a binuclear D-shaped macrocycle, tetranuclear open-ended cagelike frameworks, and duplex metallotweezer stacking structures. Furthermore, a rare stacking interaction resulting in selective C-H activation was observed during the self-assembly process of these elaborate architectures.

A novel template-free Cp*Rh-based molecular Solomon link has been established through selection of the flexible ligand L as a linker and the half-sandwich rhodium(III) dinuclear fragment B1 as a rigid capping unit. Furthermore, we demonstrate that the self-assembly of the Solomon link based on the flexible ligand is both solvent- and concentration-dependent: the Solomon link is formed in concentrated methanolic solutions, whereas formation of a dinuclear trapezoidal rectangle is favored at low concentrations or in acetonitrile or DMF solutions. Remarkably, alteration of the solvent or concentration can promote a unique and dynamic interconversion between the two molecular species, accompanying conformational change of the ligand. The synthetic outcomes are supported by single-crystal X-ray diffraction analysis.

A stepwise self-assembly protocol has been used to synthesize [2]- and [3]catenanes. Firstly, binuclear Cp*Rh/Ir-directed (Cp*=pentamethylcyclopentadienyl) pseudorotaxanes were prepared through self-assembly, driven by donor-acceptor interactions between electron-deficient naphthalenediimide (NDI) units and an electron-rich crown ether. Subsequently, the pre-organized pseudorotaxanes were applied as tectons for self-assembly of [2]- and [3]catenanes by combination with very simple linkers. The structures of the catenanes were confirmed by NMR spectroscopy, ESI mass spectrometry, single-crystal X-ray diffraction analysis, and elemental analysis.

A template-free Cp*Ir-based molecular Solomon link and an unusual trefoil knot induced by stacking interactions were realized via selection of the nonrigid dipyridyl ligand 4,4'-bis(pyridin-4-ylmethyl)-1,1'-biphenyl (BpmBp). In addition, a novel heterobimetallic tetranuclear (IrIII2 + AgI2) complex featuring argentophilic interaction was synthesized in high yield. Remarkably, the reversible topological transformation between the Solomon link and an unusual trefoil knot can be achieved by utilizing the chemical reactivity of silver(I) ions under mild conditions, as demonstrated by a detailed X-ray crystallographic study.

Herein, we present a new synthetic approach to achieve selective supramolecular transformations and construct different interlocked metallacycles featuring a π-electron-deficient thiazolo[5,4-d]thiazole-derived ligand. We demonstrate that the formation of mono-rings, interlocked rings ([2]catenanes) and Borromean rings can be controlled by adjusting the length of the binuclear half-sandwich RhIII and IrIII building blocks. Furthermore, a concentration effect or D-A stacking interaction between the pyrene guest and the thiazolo[5,4-d]thiazole-based ligand promotes a unique and reversible conversion between catenane structures and metalla-rectangles. The synthetic results are supported by single-crystal X-ray diffraction analysis.

A series of supramolecular transformation cascades are presented here, employing ligand exchange reactions, concentration-dependent Borromean ring (BR) linking and unlinking, and inverse electron-demand Diels-Alder (IEDDA) reactions. The new family of template-free, tetrazine-edged BRs are constructed by using ligand exchange reactions, and their concentration-dependent linking and unlinking reactions have been observed. Moreover, Borromean precursors have been demonstrated to further undergo supramolecular structural transformations induced by rapid and efficient IEDDA reactions to afford corresponding post-assembly modified architectures. Remarkably, subtle steric increases of the pyridazine fragments obtained by IEDDA reactions is regarded to induce controlled topological transformations in the cascade, unlinking the Borromean structures by using electron-rich dienophiles as triggering signals.

Two Cp*-RhIII based trefoil knots were obtained in high yield under ambient conditions via the coordination-driven self-assembly of semi-rigid thioether dipyridyl ligand 1,4-bis[(pyridin-4-ylthio)methyl]benzene (L1 ), ligand chloranilic acid (H2 -CA) and 6,11-dihydroxytetracene-5,12-dione (H2 -TtDo) with Cp*RhIII metal corner units, respectively. Furthermore, using the bulkier 4,4'-{[(2,5-dimethyl-1,4-phenylene)bis(methylene)]bis(sulfanediyl)}dipyridine (L2 ) in the place of ligand L1 in the construction process resulted in the formation of a teranuclear metallacycle and a template-free Borromean ring in high yields thanks to significantly altered intermolecular forces between the constituent ligands induced by the sterically-hindering methyl groups of L2 , as demonstrated via a detailed X-ray crystallographic analysis and NMR spectroscopy.

Herein, we describe the design and synthesis of three tetranuclear complexes, [(Cp*Rh)(L1)]4(OTf)4 (1a, HL1 = 2-(pyridin-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline), [(Cp*Ir)(L1)]4(OTf)4 (1b), and [(Cp*Rh)(L2)]4(OTf)4 (2, HL2 = 2-(4-(pyridin-4-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline). Owing to the precise design of the phenanthroline-derived ligands, these complexes exhibit perfect square-shaped structures with side lengths of 13.53, 13.57, and 17.95 A, respectively. These molecules orderly align and assemble into square-shaped, one-dimensional nanotubes. The molecular structures and arrangement of the nanotubes were evidenced by single-crystal X-ray diffraction. Solution behavior was studied by NMR spectroscopy. Fourier transform infrared spectroscopy and elemental analysis were also employed to characterize these complexes.

A series of Cp*Rh-based molecular Borromean rings (BRs) are prepared from naphthazarine or metallaligand. Some of as-synthesized BRs display high stability and are formed in high yields in solution. The reason is related to the length ratio of the long-arm linker and short-arm linker, where smaller aspect ratios of the metallarectangles promote improved stability and yields of the BRs in solution. Increasing the width of the metallaligand or pyridyl ligand hinders the formation of BRs and leads to unoccupied monomeric rectangles, which were further used as catalysts for the acyl transfer reaction between N-acetylimidazole and (4-(pyridin-4-yl)phenyl) methanol.

For the first time, carborane complexes containing a B(4)–S bond were obtained directly by heating mononuclear Pd-B(4)-bound carborane complexes. A possible mechanism involved in sulfur atom migration is presented in which the leaving group, pyridine, benzyl isocyanide or PPh3, is demonstrated to be the trigger of the reaction process. In this work, efficient routes are developed through one-pot reactions to prepare B(4)-S carborane derivatives.

Different types of multinuclear half-sandwich rhodium macrocycles and cages were designed and synthesized by using two similar multifunctional hydroxamate ligands (pyrazine-2-hydroxamic acid (NaHL1 ) and 4,4'-bipyridine-2-hydroxamic acid (KHL2 )) featuring one monodentate site and two pairs of chelating sites. The RhIII -PdII heterometallic macrocycles were constructed by using the semi-open palladium(II) source [Pd(en)Cl2 ] with two free acceptor sites. However, only one kind of macrocycle was found when the shorter ligand L1 was used, while in for the larger ligand, various spectroscopic techniques demonstrated the coexistence of hexanuclear and octanuclear macrocycles in solution and the proportions of both components depended on concentration and temperature. The palladium salt Pd(NO3 )2 , as a source of "naked" Pd2+ , was introduced to assemble the cuboid-shaped cage composed of two types of metal ions and three types of organic ligands. In addition, two silver(I)-containing mixed-metal complexes bridged by pyrazine were obtained, in which two forms of decanuclear complex with C2v and C2h point symmetry cocrystallized-one is a polymeric structure and the other is a discrete cage. However, the third form, with D2 point symmetry, was found in the larger cage.

Summary A series of Cp*Rh- and Cp*Ir-based molecular Borromean rings (BRs) have been prepared with dihalogenated ligands (fluoranilic acid, chloranilic acid, and bromianilic acid) and 4,4′-bipyridylacetylene. The halogen atoms play a crucial role in forming BRs. The strength of the interaction among the rings for different BRs is not the same and can be adjusted by changes in the halogen atoms on the precursor. We took advantage of this dissimilarity in the interactions to realize selective reversible conversion between BRs and a monomeric rectangle by the use of different p -dihalobenzenes. Subsequently, a stepwise separation method for p -dichlorobenzene, p -dibromobenzene, and p -diiodobenzene at ambient temperature was developed. The BRs used in the separation are recoverable and recyclable.

Understanding and controlling the topology of self-assembled structures plays a fundamental role in supramolecular chemistry. Herein, the preparation of a series of tetranuclear metallarectangles and hexanuclear trefoil knots featuring Cp*Rh building blocks by template-free self-assembly with four different rigid and flexible ligands is described. Transformations between the trefoil knots and the corresponding macrocycles can be induced by using concentration effects. Remarkably, the hexanuclear trefoil knot 5 was shown to assemble further to provide rare examples of [12+1] heteronuclear double trefoil knots (5 a/5 b/5 c/5 d) through coordination of the amide oxygen atoms to the secondary metal ions Na+ /K+ /Ca2+ /Cd2+ . The synthetic results are supported by single-crystal XRD.

The use of geminal di(guanidinium) and acridin-9(10H)-one-derived di(carboxylate) derivatives (1a-c and 2a-e, respectively) allows stabilization of heterodimers characterized by high binding affinities in water (maximum ΔG 105 M-1) as inferred from UV-vis spectroscopic titrations and ITC measurements, therefore rivaling or surpassing the interaction energy between the strongest DNA or RNA triplet pairs. These duplexes are readily accessible and are structurally modifiable, rendering them attractive as building blocks for creating heteroduplex constructs. Incorporating poly(ethylene glycol)-decorated benzyl groups into the dicarboxylate, allows formation of hydrogels in the case of 1b-2c.

Over the past decades, molecular knots and links have captivated the chemical community due to their promising mimicry properties in molecular machines and biomolecules and are being realized with increasing frequency with small molecules. Herein, we describe how to utilize stacking interactions and hydrogen-bonding patterns to form trefoil knots, figure-eight knots and [2]catenanes. A transformation can occur between the unique trefoil knot and its isomeric boat-shaped tetranuclear macrocycle by the complementary concentration effect. Remarkably, the realization and authentication of the molecular figure-eight knot with four crossings fills the blank about 41 knot in knot tables. The [2]catenane topology is obtained because the selective naphthalenediimide (NDI)-based ligand, which can engender favorable aromatic donor-acceptor π interactions due to its planar, electron-deficient aromatic surface. The stacking interactions and hydrogen-bond interactions play important roles in these self-assembly processes. The advantages provide an avenue for the generation of structurally and topologically complex supramolecular architectures., Molecular knots and links continue to fascinate synthetic chemists. Here, the authors use stacking and hydrogen-bonding interactions between a set of similar building blocks to construct several complex molecular topologies, including a figure-eight knot and a trefoil knot.

In this work, a pincer-type complex [Cp*Ir-(SNPh)(SNHPh)(C2 B10 H9 )] (2) was synthesized and its reactivity studied in detail. Interestingly, molecular hydrogen can induce the transformation between the metalloradical [Cp*Ir-(SNPh)2 (C2 B10 H9 )] (5. ) and 2. A mixed-valence complex, [(Cp*Ir)2 -(SNPh)2 (C2 B10 H8 )] (7.+ ), was also synthesized by one-electron oxidation. Studies show that 7.+ is fully delocalized, possessing a four-centered-one-electron (S-Ir-Ir-S) bonding interaction. DFT calculations were also in good agreement with the experimental results.

Herein, we describe how to utilize stacking interactions to achieve selective supramolecular transformation and molecular Borromean rings (BRs). By using a dinuclear naphthalenediimide (NDI)-based Cp*Rh acceptor and linear bipyridyl ligands, organometallic rectangles featuring dynamic behavior have been constructed. Unique discrete aromatic stacking arrays were formed by inducing pyrene units as guest molecules. The topology of the BRs was realized by the use of a strategically chosen ligand which was capable of participating in D-A interactions and hydrogen bonding, as evidenced from single-crystal X-ray analysis and computational studies. These self-assembly processes underline the advantages of dynamic bonding and π-π stacking interactions, and serve to illustrate a new approach to generating structurally and topologically nontrivial supramolecular architectures.

Doped nanoparticles (especially bimetal doped nanoparticles) have attracted extensive interest not only for fundamental scientific research but also for application purposes. However, their indefinite composition (structure) and broad distribution hinder an insightful understanding of the interaction between these invasive metals in bimetal doped nanoparticles. Fortunately, atom-precise bimetal doped ultrasmall nanoparticles (nanoclusters) provide opportunities to obtain such insights. However, atom-precise trimetal nanoclusters and their structures have rarely been reported. Here, we successfully dope thiolated Au25 nanoclusters with Hg and Ag successively by using a biantigalvanic reduction method. We then fully characterize the as-obtained trimetal nanoclusters using multiple techniques (including single-crystal X-ray crystallography), and we demonstrate that the mercury and silver dopings exhibit not only a synergistic but also a counteractive influence on some of the physicochemical properties of Au25.

The structural features that render gold nanoclusters intrinsically fluorescent are currently not well understood. To address this issue, highly fluorescent gold nanoclusters have to be synthesized, and their structures must be determined. We herein report the synthesis of three fluorescent Au24 (SR)20 nanoclusters (R=C2 H4 Ph, CH2 Ph, or CH2 C6 H4 (t) Bu). According to UV/Vis/NIR, differential pulse voltammetry (DPV), and X-ray absorption fine structure (XAFS) analysis, these three nanoclusters adopt similar structures that feature a bi-tetrahedral Au8 kernel protected by four tetrameric Au4 (SR)5 motifs. At least two structural features are responsible for the unusual fluorescence of the Au24 (SR)20 nanoclusters: Two pairs of interlocked Au4 (SR)5 staples reduce the vibration loss, and the interactions between the kernel and the thiolate motifs enhance electron transfer from the ligand to the kernel moiety through the Au-S bonds, thereby enhancing the fluorescence. This work provides some clarification of the structure-fluorescence relationship of such clusters.

A series of molecular metalla[2]catenanes featuring Cp*Ir vertices have been prepared by the template-free, coordination-driven self-assembly of dinuclear iridium acceptors and 1,5-bis[2-(4-pyridyl)ethynyl]anthracene donors. The metalla[2]catenanes were formed by using a strategically selected linker type that is capable of participating in sandwich-type π-π stacking interactions. In the solid state, the [2]catenanes adopt two different configurations depending on the halogen atoms at the dinuclear metal complex bridge. Altering the solvent or the concentration, as well as the addition of guest molecules, enabled controlled transformations between metalla[2]catenanes and tetranuclear metallarectangles.

A series of metallosupramolecular architectures have been prepared, including rectangles, prisms and cages, that feature half-sandwich rhodium(III) fragments at the vertices. Remarkably, a stable cage-like heteropolymetallic complex possessing eight rhodium(III) and two silver(I) metal ions (3) has been obtained following a multistep procedure. The RhIII /AgI mixed macrocage enables the separation of dihalogenated benzene derivatives with high selectivity. Furthermore, a detailed X-ray crystallographic study confirmed that the discriminative encapsulation of para-dihalobenzene (dichlorobenzene, dibromobenzene and diiodobenzene) is favored by Ag-π interactions and steric effects.

Controlling the dopant type, number, and position in doped metal nanoclusters (nanoparticles) is crucial but challenging. In the work described herein, we successfully achieved the mono-cadmium doping of Au25 nanoclusters, and revealed using X-ray crystallography in combination with theoretical calculations that one of the inner-shell gold atoms of Au25 was replaced by a Cd atom. The doping mode is distinctly different from that of mono-mercury doping, where one of the outer-shell Au atoms was replaced by a Hg atom. Au24Cd is readily transformed to Au24Hg, while the reverse (transformation from Au24Hg to Au24Cd) is forbidden under the investigated conditions.

In modern coordination chemistry, supramolecular coordination complexes take advantage of ligand design to control the shapes and sizes of such architectures. Here we describe how to utilize starting building blocks and a multifunctional ligand to rationally design and synthesize different types of discrete assemblies. Using a hydroxamate ligand featuring two pair of chelating sites together with half-sandwich iridium and rhodium fragments, we were able to construct a series multinuclear organometallic macrocycles and cages through stepwise coordination-driven self-assembly. Experimental observations, supported by computational work, show that selective coordination modes were ascribed to the significant electronic density differences of the two chelating sites, (O,O') and (N,N'). The results underline the advantages of the discrimination between soft and hard binding sites, and suggest that hydroxamic acids can be used as a versatile class of facile multifunctional scaffold for the construction of novel two-dimensional and three-dimensional architectures.

Template-free molecular Borromean rings (BRs) and open-ended molecular capsules were realized by strategic selection of the polypyridyl ligand tetrapyrido[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j] phenazine (TPPHZ) with a large surface area and specific geometry. The topology of these intricate architectures was constructed via precisely controlled stacking interactions, as evidenced from single-crystal X-ray analysis.

In contrast to conventional stepwise synthesis of molecular Borromean rings, a self-assembly synthetic method which proceeds without the aid of a template has been developed. In the formation of molecular rectangles, by adjustment of the long-arm length of the rectangles, a series of size-dependent Borromean-link frameworks were constructed. Both the shortest length of two arms and the relative proportion of the length of the long arm to that of the short arm play a key role in the formation of Borromean rings. DFT calculations were used to provide theoretical support for the formation of discrete interlocked frameworks.

A chelation-directed self-sorting synthesis of a series of cationic heterometallic coordination cages (HCCs) with tunable sizes is described. Two complexation modes were found in the cage-forming process. Metal-anchoring host-guest behavior and size-selective in-cage catalytic activities were found for the HCCs.

A series of half-sandwich iridium-based complexes bearing 1,4-benzenebis (N,N′-dicyclohexylamidine) (H2 L 1) or 4,4′-bisphenylbis(N,N′-dicyclohexylamidine) (H2 L 2) has been synthesized and characterized. Treatment of [Cp*IrCl2]2 (Cp* = η5 -pentamethyl-cyclo pentadienyl) with deprotonated H2 L 1 or H2 L 2 at low temperature resulted in formation of binuclear complexes [Cp*IrCl]2 (L 1) and [Cp*IrCl]2(L 2). They were chosen as precursors to construct macrocycles and cages. Tetranuclear metallamacrocycles [(Cp*Ir)4(L 1)2 (pyrazine)2][OTf]4 and [(Cp*Ir)4(L 2)2(pyrazine)2][OTf]4 were assembled by the reaction of complex [Cp*IrCl]2 (L 1) or [Cp*IrCl]2(L 2) with pyrazine after the removal of chloride from the iridium centers with silver salt AgOTf (OTf = O2SCF3). When 2,4,6-tri(4-pyridyl)-1,3,5-triazine (tpt) is used instead of pyrazine under the same conditions, hexanuclear metallacages [(Cp*Ir)6(L1 )3(tpt)2][OTf]6 and [(Cp*Ir)6(L 2)3(tpt)2][OTf]6 were formed. Single-crystal X-ray analysis indicated that the cation of complex [(Cp*Ir)4(L 1)2 (pyrazine)2][OTf]4 is a rectangular structure, while the cation of complex [(Cp*Ir)4(L 2)2(pyrazine)2][OTf]4 is seriously distorted, nearly to a tetrahedral state. Moreover, complexes [(Cp*Ir)6(L1 )3(tpt)2][OTf]6 and [(Cp*Ir)6(L 2)3(tpt)2][OTf]6 are prism-like cages with large cavity size, which can be prepared in very high yield in the absence of templates. Surprisingly, solutions of multinuclear complexes are very sensitive to carbon monoxide, in which the frameworks were destroyed, giving the binuclear complexes [(Cp*Ir)2(CO)2(L 1)][OTf]2 and [(Cp*Ir)2(CO)2(L 2)][OTf]2.

Theseanalogies provide promising ideas for the self-assembly ofnovel supramolecular systems based on anion coordination.In the past few decades, zero-dimensional, aestheticallypleasing metal coordination complexes, such as molecularsquares, capsules, tetrahedra, and other complex polyhedralshapes, have attracted much interest.

Two isostructural porous 3d–4d materials [M(cyclam)Pd(2,4-pydc)2·4H2O]n (2,4-H2pydc = pyridine-2,4-dicarboxylate acid) (1, M = Ni and 2, M = Zn) and five other isostructural complexes {[M′(cyclam)]2[M(2,5-pydc)3]·xH2O}n (2,5-H2pydc = pyridine-2,5-dicarboxylate acid) (3, M = Co, M′ = Ni; 4, M = M′ = Ni; 5, M = Zn, M′ = Ni; 6, M = Ni, M′ = Zn and 7, M = M′ = Zn) were synthesized. Both complexes 1′ and 2′ show high selective CO2 capture over CH4 and N2. The comparisons of different gas sorption properties between 1′ and 2′ strongly suggest that metal identity has a great influence on the polarity of frameworks, but just the polar molecules respond to the polarity changes of different frameworks. The comparisons of CO2 sorption properties between five other isostructural complexes 3′–7′ also strongly suggest that metal identity has great influence on polarity of frameworks and further the CO2 uptake.