Selective Construction and Structural Transformation of Homogeneous Linear Metalla[4]catenane and Metalla[2]catenane Assemblies.

Although the synthesis of mechanically interlocked molecules has been extensively researched, selectively constructing homogeneous linear [4]catenanes remains a formidable challenge. Here, we selectively constructed a homogeneous linear metalla[4]catenane in a one-step process through the coordination-driven self-assembly of a bidentate benzothiadiazole derivative ligand and a binuclear half-sandwich rhodium precursor. The formation of metalla[4]catenanes was facilitated by cooperative interactions between strong sandwich-type π-π stacking and non-classical hydrogen bonds between the components. Moreover, by modulating the aromatic substituents on the binuclear precursor, two homogeneous metalla[2]catenanes were obtained. The molecular structures of these metallacatenanes were unambiguously characterized by single-crystal X-ray diffraction analysis. Additionally, reversible structural transformation between metal-catenanes and the corresponding metallarectangles could be achieved by altering their concentration, as confirmed by mass spectrometry and NMR spectroscopy studies.

Trefoil-Shaped Metal-Organic Cages as Fluorescent Chemosensors for Multiple Detection of Fe3+, Cr2O72-, and Antibiotics.

The construction of metal-organic cages (MOCs) with specific structures and fluorescence sensing properties is of much importance and challenging. Herein, a novel phenanthroline-based metal-organic cage, [Cd3L3·6MeOH·6H2O] (1), was synthesized by metal-directed assembly of the ligand 3,3'-[(1E,1'E)-(1,10-phenanthroline-2,9-diyl)bis(ethene-2,1-diyl)]dibenzoic acid (H2L) and CdI2 using a solvothermal method. According to single-crystal X-ray analysis, cage 1 exhibits a rare trefoil-shaped structure. Meanwhile, the discrete MOCs are further stacked into a 3D porous supramolecular structure through abundant intermolecular C-H···O interactions. Additionally, through exploration of fluorescence sensing on cations, anions, and antibiotics in aqueous solution, the experimental results indicate that cage 1 has excellent fluorescence sensing abilities for Fe3+, Cr2O72-, and nitrofuran and nitroimidazole antibiotics. The sensing ability of 1 remains unaltered for five cycles toward all analytes. The above results suggested that cage 1 can be considered a potential multiple sensor for the detection of Fe3+, Cr2O72-, and some antibiotics.

A Chiral Metal-Organic Framework Prepared on Large-Scale for Sensitive and Enantioselective Fluorescence Recognition.

MOF-based luminescent sensors have garnered considerable attention due to their potential in recognition and discrimination with high sensitivity, selectivity, and fast response in the last decades. Herein, this work describes the bulk preparation of a novel luminescent homochiral MOF, namely, [Cd(s-L)](NO3)2 (MOF-1), from an enantiopure pyridyl-functionalized ligand with rigid binaphthol skeleton under mild synthetic condition. Except for the features of porosity and crystallinity, the MOF-1 has also been characterized with water-stability, luminescence, and homochirality. Most important, the MOF-1 exhibits highly sensitive molecular recognition toward the4-nitrobenzoic acid (NBC) and moderate enantioselective detection of proline, arginine, and 1-phenylethanol.

Template-Free Self-Assembly of Molecular Trefoil Knots and Double Trefoil Knots Featuring Cp*Rh Building Blocks.

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.

Highly Selective Synthesis of Iridium(III) Metalla[2]catenanes through Component Pre-Orientation by π⋠⋠⋠π†Stacking.

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 general strategy to generate oxygen vacancies in bimetallic layered double hydroxides for water oxidation.

A general electrocatalyst design for water splitting through generating oxygen vacancies in bimetallic layered double hydroxides by using carbon nitride is proposed. The excellent OER activity of the achieved bimetallic layered double hydroxides is attributed to oxygen vacancies, which reduce the energy barrier of the rate-determining step.

Self-Assembled Au Nanoparticle Arrays for Precise Metabolic Assay of Cerebrospinal Fluid.

Precise and rapid monitoring of metabolites in biofluids is a desirable but unmet goal for disease diagnosis and management. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) exhibits advantages in metabolite analysis. However, the low accuracy in quantification of the technique limits its transformation to clinical usage. We report herein the use of Au nanoparticle arrays self-assembled at liquid-liquid interfaces for mass spectrometry (MS)-based quantitative biofluids metabolic profiling. The two-dimensional arrays feature uniformly and closely packed Au nanoparticles with 3 nm interparticle gaps. The experimental study and theoretical simulation show that the arrays exhibit high photothermal conversion and heat confinement effects, which enhance the laser desorption/ionization efficacy. With the nanoscale roughness, the AuNP arrays as laser desorption/ionization substrates can interrupt the coffee-ring effect during droplet evaporation. Therefore, high reproducibility (RSD <5%) is obtained, enabling accurate quantitative analysis of diverse metabolites from 1 µL of biofluids in seconds. By quantifying glucose in the cerebrospinal fluid (CSF), it allows us to identify patients with brain infection and rapidly evaluate the clinical therapy response. Consequently, the method shows potential in advanced metabolite analysis and biomedical diagnostics.

Coordination-driven self-assembly of a molecular figure-eight knot and other topologically complex architectures.

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.

Light-initiated reversible conversion of macrocyclic endoperoxides derived from half-sandwich rhodium-based metallarectangles.

Although reversible photo-dimerization or oxygenation of anthracene and its derivatives is a common reaction, light-initiated reversible conversion of endoperoxide organometallic frameworks has only rarely been addressed. Herein, a series of tetranuclear organometallic macrocycles, [Cp*2Rh2(µ-C2O4-κO)]2(BP4VA)2(OTf)4 (4), [Cp*2Rh2(BiBzIm)]2(BP4VA)2(OTf)4 (5), and [Cp*2Rh2(DHBQ)]2(BP4VA)2(OTf)4 (6), were obtained in good yields from the reactions of the binuclear half-sandwich rhodium precursors [Cp*2Rh2(µ-C2O4-κO)Cl2] (1), [Cp*2Rh2(BiBzIm)Cl2] (2), and [Cp*2Rh2(DHBQ)Cl2] (3) with the 9,10-bis((E)-2-(pyrid-4-yl)vinyl)anthracene (BP4VA) ligand. The photochemical reaction of these metallarectangles was investigated by NMR and UV/vis spectroscopy. We have demonstrated that complexes 4, 5, and 6 can be reversibly and nearly quantitatively converted to the macrocyclic endoperoxides 4-O2, 5-O2, and 6-O2. Meanwhile, the structure of the endoperoxide photoproducts was unambiguously confirmed by 1H/13C NMR spectroscopy, IR spectroscopy, elemental analyses, and X-ray crystallography.

A nonanuclear triangular macrocycle and a linear heptanuclear heterometallic complex based on a 2-substituted imidazole-4,5-dicarboxylate ligand.

A Cp*Rh-based nonanuclear triangular macrocycle complex [(Cp*Rh)9L3(NO3)4.5(MeOH)](OTf)4.5 (1), a Cp*Ir-based trinuclear complex [(Cp*Ir)3L(MeCN)4](OTf)3 (2) and a linear heptanuclear heterometallic complex [(Cp*Ir)6ZnL2(MeCN)8(MeOH)2](OTf)8 (3) (Cp* = η(5)-pentamethylcyclopentadienyl) have been synthesized from a 2-(4-(pyridin-4-yl)phenyl)-1H-imidazole-4,5-dicarboxylic acid proligand. These complexes were further characterized by X-ray crystallography, (1)H NMR, DOSY NMR, IR spectroscopy, and elemental analyses.

Structural and luminescence modulation in 8-hydroxyquinolinate-based coordination polymers by varying the dicarboxylic acid.

Two Zn(ii) and Cd(ii) coordination polymers [ZnL2·2DMF] (1) and [CdL(OAc)] (2) were first synthesized by treating a novel 2-substituted 8-hydroxyquinolinate ligand HL involving a pyridyl group with zinc or cadmium salts. Two dicarboxylic acid ligands (H2BDC = 1,4-benzenedicarboxylic acid; H2BPDC = 4,4'-biphenyldicarboxylic acid) are employed as secondary auxiliary ligands to perform a systematic study on the structural diversities in the M(ii)-quinolinate frameworks. By introducing two dicarboxylate anions in the reaction system, four new polymers [Zn2L2(BDC)] (3), [Zn3L2I2(BPDC)·2MeOH·8H2O] (4), [Cd2L2(BDC)] (5) and [Cd2L2(BPDC)·2MeOH·4H2O] (6) were obtained. Complex 1 possesses a two-dimensional (2D) square grid containing meso-helical chains. Complex 2 is a 2D network fabricated by binuclear {Zn2} secondary building units (SBUs). Complexes 3 and 5 show a kind of 2D structure constructed by cyclic hexamers Zn6L4, which are divided into half by the coordinated BDC. In complex 4, the BPDC ligands bridge the 1D M(ii)-L chains into a 2D layered structure. Complex 6 presents an interesting 3D structure, in which the BPDC ligands link the binuclear Cd(ii) units into many meso-helical chains along the a and b axes. The diverse structures of complexes 1-6 indicate that the skeletons of dicarboxylate anions play an important role in the assembly of such different frameworks. Moreover, distinct fluorescence properties (emission wavelength and lifetime) of the complexes 1-6 were observed in the solid state.

Self-assembly of five 8-hydroxyquinolinate-based complexes: tunable core, supramolecular structure, and photoluminescence properties.

Five new Zn(II) complexes, namely [Zn(3)(L)(6)] (1), [Zn(2)(Cl)(2)(L)(2) (py)(2)] (2), [Zn(2)(Br)(2) (L)(2)(py)(2)] (3), [Zn(L)(2)(py)] (4), and [Zn(2)(OAc)(2)(L)(2)(py)(2)] (5), were prepared by the solvothermal reaction of ZnX(2) (X(-) =Cl(-), Br(-), F(-), and OAc(-)) salts with a 8-hydroxyquinolinate ligand (HL) that contained a trifluorophenyl group. All of the complexes were characterized by elemental analysis, IR spectroscopy, and powder and single-crystal X-ray crystallography. The building blocks exhibited unprecedented structural diversification and their self-assembly afforded one mononuclear, three binuclear, and one trinuclear Zn(II) structures in response to different anions and solvent systems. Complexes 1-5 featured four types of supramolecular network controlled by non-covalent interactions, such as π⋅⋅⋅π-stacking, C-H⋅⋅⋅π, hydrogen-bonding, and halogen-related interactions. Investigation of their photoluminescence properties exhibited disparate emission wavelengths, lifetimes, and quantum yields in the solid state.

Three Mn(II) coordination polymers with a bispyridyl-based quinolinate ligand: the anion-controlled tunable structural and magnetic properties.

Three new Mn(ii) coordination polymers, namely [Mn3L6·2H2O] (), [MnL2] (), and [MnL2·2H2O] (), were prepared by solvothermal reactions of Mn(ii) salts with a bispyridyl-based quinolinate ligand. All complexes were characterized by elemental analysis, IR spectra, powder and single-crystal X-ray crystallography. Single crystal X-ray studies show that these coordination polymers exhibit a structural diversification due to the different counteranions (OAc(-), Cl(-), and NO3(-)). Complex has a 2D supramolecular structure with a cyclic tetramer Mn3L6 secondary building unit. Complex possesses a rhombohedral grid network containing a type of meso-helical chain (P + M) constructed via the metal-ligand coordination interaction. Complex features a 3D non-porous structure based on the arrangement of 2D grids. Magnetic susceptibility measurements indicate that the three Mn(ii) polymers show disparate magnetic properties due to their different supramolecular structures.