Hierarchical Self-Assembly of Capsule-Shaped Zirconium Coordination Cages with Quaternary Structure.

Biological macromolecules exhibit emergent functions through hierarchical self-assembly, a concept that is extended to design artificial supramolecular assemblies. Here, the first example of breaking the common parallel arrangement of capsule-shaped zirconium coordination cages is reported by constructing the hierarchical porous framework ZrR-1. ZrR-1 adopts a quaternary structure resembling protein and contains 12-connected chloride clusters, representing the highest connectivity for zirconium-based cages reported thus far. Compared to the parallel framework ZrR-2, ZrR-1 demonstrated enhanced stability in acidic aqueous solutions and a tenfold increase in BET surface area (879 m2  g-1 ). ZrR-1 also exhibits excellent proton conductivity, reaching 1.31 × 10-2 S·cm-1 at 353 K and 98% relative humidity, with a low activation energy of 0.143 eV. This finding provides insights into controlling the hierarchical self-assembly of metal-organic cages to discover superstructures with emergent properties.

Chiral proline-substituted porous organic cages in asymmetric organocatalysis.

The efficient preparation of chiral porous organic cages (POCs) with specific functions is challenging, and their application in asymmetric catalysis has not previously been explored. In this work, we have achieved the construction of chiral POCs based on a supramolecular tetraformyl-resorcin[4]arene scaffold with different chiral proline-modified diamine ligands and utilizing dynamic imine chemistry. The incorporation of V-shaped or linear chiral diamines affords the [4 + 8] square prism and [6 + 12] octahedral POCs respectively. The appended chiral proline moieties in such POCs make them highly active supramolecular nanoreactors for asymmetric aldol reactions, delivering up to 92% ee. The spatial distribution of chiral catalytic sites in these two types of POCs greatly affects their catalytic activities and enantioselectivities. This work not only lays a foundation for the asymmetric catalytic application of chiral POCs, but also contributes to our understanding of the catalytic function of biomimetic supramolecular systems.

Dynamic metal-organic frameworks for the separation of hydrogen isotopes.

Reversible structural transformation upon exposure to external stimuli can lead to breathing effect or gate-opening phenomena for dynamic metal-organic frameworks (MOFs), which endow them with excellent gas separation performance. The separation of hydrogen isotopes remains a huge challenge due to their nearly identical physical and chemical properties. The unique feature of dynamic MOFs, especially structural transition triggered by isotopes or by temperature, maximally enhances kinetic quantum sieving and contributes to the highly selective separation of hydrogen isotopes. Herein, we present some examples for the separation of hydrogen isotopes based on dynamic frameworks, and we expect to attract increasing attention to this research field.

The Combination of Charge and Energy Transfer Processes in MOFs for Efficient Photocatalytic Oxidative Coupling of Amines.

Combining electron and energy transfer processes is very significant for efficient photocatalytic oxidation of organic molecules. The first synthesized MOF, Co2(L)(2,6-NDC)2·xguest (FJI-Y10, L = bis(N-pyridyl) tetrachloroperylene peryleneimide, 2,6-NDC = 2,6-naphthalenedicarboxylic acid, FJI = Fujian Institute), shows a 2-fold interpenetrated pcu net, in which the 2,6-NDC ligand connects typical Co2(COO)4 paddle wheel clusters to form square lattices pillared by new PDI-type ligand L. FJI-Y10 as a heterogeneous and recyclable photocatalyst is applied for photo-oxidation of benzylamine and its derivatives with an excellent yield of 100%, which is much higher than that (59%) of the equivalent L ligand as a homogeneous photocatalyst under the same reaction conditions. Such a high-efficiency photocatalytic activity attributes to the combination of charge and energy transfer processes in catalyst FJI-Y10 during the catalytic process.

A Reusable MOF-Supported Single-Site Zinc(II) Catalyst for Efficient Intramolecular Hydroamination of o-Alkynylanilines.

The exploitation of new and active earth-abundant metal catalysts is critical for sustainable chemical production. Herein, we demonstrate the design of highly efficient, robust, and reusable ZnII -bipyridine-based metal-organic framework (MOF) catalysts for the intramolecular hydroamination of o-alkynylanilines to indoles. Under similar conditions homogeneous catalytic systems mainly provide hydrolysate. Our results prove that MOFs support unique internal environments that can affect the direction of chemical reactions. The ZnII -catalyzed hydroamination reaction can be conducted without additional ligands, base, or acid, and is thus a very clean reaction system with regard to its environmental impact.

Optimizing H2, D2, and C2H2 Sorption Properties by Tuning the Pore Apertures in Metal-Organic Frameworks.

By adjustment of the arm lengths of two triphenylamine-based ligands, two nearly isostructural metal-organic frameworks (MOFs), namely, the reported nanoporous FIR-29 (FIR = Fujian Institute of Research) and the new microporous FJI-Y9 (FJI = Fujian Institute), are obtained, and all exhibit honeycomb lattices of hexagonal channels with Ca-COO chains connected by tris[(4-carboxyl)phenylduryl]amine (H3TCPA) ligands and 4,4',4''-nitrilotribenzoic acid (H3NTB) ligands, respectively. Although the Brunauer-Emmett-Teller (BET) surface area (1117 m2 g-1) and pore size (8.5 Å) of FJI-Y9 are much lower than those (BET surface area of 2061 m2 g-1 and pore size of 16 Å) of the reported FIR-29 because of the shorter arm lengths of H3NTB, the activated FJI-Y9-ht shows high H2 (202.3 cm3 g-1) and D2 (221.9 cm3 g-1) uptake under 77 K and 1 bar and C2H2 uptake of 168.9 cm3 g-1 under 273 K and 1 bar, which are all at least 48% enhancement over those of FIR-29-ht. The above results indicate that small pores in MOFs are beneficial to the uptake of some special gases including H2, D2, C2H2, etc.

A new metal-organic framework constructed from cationic nodes and cationic linkers for highly efficient anion exchange.

A novel cationic metal-organic framework, FJI-Y6, was designed and constructed by combining [In3O(COO)6(H2O)3]+ with cationic linkers. FJI-Y6 exhibits highly efficient anion exchangeability. For example, Acid orange 7, with a single negative charge and which cannot be adsorbed effectively by previously reported MOFs, is captured and released rapidly by FJI-Y6.

From Coordination Cages to a Stable Crystalline Porous Hydrogen-Bonded Framework.

A stable framework has been constructed through multiple charge-assisted H-bonds between cationic coordination cages and chloride ions. The framework maintained its original structure upon desolvation, which has been established by single-crystal structure analysis. This is the first fully characterized stable porous framework based on coordination cages after desolvation, with a moderately high Brunauer-Emmett-Teller (BET) surface area of 1201 m2 g-1 . This work will not only give a light to construct stable porous frameworks based on coordination cages and thus broaden their applications, but will also provide a new avenue to the assembly of other porous materials such as porous organic cages and hydrogen-bonded organic frameworks (HOFs) through non covalent bonds.

Controlled Orthogonal Self-Assembly of Heterometal-Decorated Coordination Cages.

Multiple orthogonal coordinative interactions were utilized to construct heterometal-decorated tetrahedral cages from in situ formed trinuclear ZrIV clusters through the combination with other metal ions such as CuII or PdII . Through effective use of the hard/soft acid/base principle, the orthogonal self-assembly process of Zr-bpydc-CuCl2 (H2 bpydc=2,2-bipyridine-5,5-dicarboxylic acid) can be finely controlled using three strategies: post-synthetic metallization, a stepwise metalloligand approach, or a one-pot reaction.

In situ construction of a coordination zirconocene tetrahedron.

The current study describes the first in situ synthesis and characterization of a new family of cationic coordination tetrahedra of both the V4F4 and V4E6 type, which are constructed by a new building block based on a trinuclear zirconocene moiety and the dicarboxylate or tricarboxylate anions.

Bipyridinium array-type porous polymer displaying hydrogen storage, charge-transfer-type guest inclusion, and tunable magnetic properties.

A multifunctional pillared-layer porous coordination polymer, {[Mn(2)(Bpybc)(ox)(2)]8 H(2)O}(n), has been constructed based on a flexible viologen derivative, 1,1'-bis(4-carboxybenzyl)-4,4'-bipyridinium dichloride (H(2)BpybcCl(2)), and an oxalate (ox) coligand. Single-crystal X-ray analysis reveals that the compound possesses multichannels with dimensions of about 6.1x6.6 A along the [110] and [-110] directions and 4.2x7.6 A along [100], and a void space of about 41.4 %. Hydrogen adsorption measurements at 77 K and 1 atm indicate that the compound exhibits a hydrogen uptake of 0.71 wt %. Owing to the incorporation of bipyridinium acceptor units, the compound can selectively accommodate aromatic donors into its nanosized pores based on charge-transfer interactions in an elastic way, and afford a specific color to different guests. Furthermore, the effect of perturbation exerted by the guest molecules on its magnetic properties has been investigated. The results indicate that the donor inclusion has little effect on its antiferromagnetic behavior, whereas dehydration of the compound decreases the strength of the magnetic exchange couplings and results in a change of the antiferromagnetic transition temperature from 14.7 to 9.8 K.

Novel polythreaded coordination polymer: from an armed-polyrotaxane sheet to a 3D polypseudorotaxane array, photo- and thermochromic behaviors.

A novel coordination compound, {[Cd(BDC)(Bpybc)(1.5)].10H(2)O}(n), obtained by the reaction of CdCl(2) with 1,1'-bis(4-carboxybenzyl)-4,4'-bipyridinium dichloride (H(2)BpybcCl(2)) and 1,4-benzenedicarboxylic acid (H(2)BDC), contains 1D polymeric chains that are comprised of alternating rings and rods and dangling lateral arms. These 1D polymeric motifs are interlaced via rotaxane-like mechanical linkages to give 2D armed-polyrotaxane sheets, which are further mutually polythreaded via pseudorotaxane-like mechanical linkages to form a 3D polypseudorotaxane array. Notably, a sandwich-type donor-acceptor-donor stacking is formed within each ring as a consequence of both types of polythreading in this species, and photoinduced and thermal-induced reduction of bipyridinium occurs with a color change from light yellow to blue.

A series of manganese-carboxylate coordination polymers exhibiting diverse magnetic properties.

The hydrothermal reactions of an asymmetrical 4-(4-carboxyphenylamino)-3,5-dinitrobenzoic acid (H2cpdba), MnCl2.4H2O, or together with 2,2'-bipyridine (2,2'-bpy) or 4,4'-bipyridine (4,4'-bpy) afford three novel molecule-based magnetic coordination polymers [Mn(cpdba)]n (1), ([Mn2(cpdba)2(2,2'-bpy)2(H2O)2].H2O)n (2) and ([Mn2(cpdba)2(4,4'-bpy)].2H2O)n (3). Compound 1 has a 3D acentric coordination network containing carboxylate-bridged 1D ladder-like manganese chains with spin-canted antiferromagnetism (J = -3.51 cm(-1) for the coupling along the ladder legs, and zJ' = 0.22 cm(-1) for coupling along the ladder rungs), whereas compounds 2 and 3 crystallize in the centrosymmetric space groups P1 and C2/c, respectively. 2 exhibits a 1D chain structure, which is extended into a 3D supramolecular network by pi-pi stacking interactions, while 3 features a quite complex 3D network built up from the cpdba(2-) and 4,4'-bpy spacers as well as the carboxylate-bridged Mn(II) chains. Both 2 and 3 show weak antiferromagnetic coupling interactions (J = -0.55 cm(-1) for 2), and a field-induced spin-flop magnetic transition can also be observed in 2 at ca. 3.2 T at 2 K.

Strong electron-accepting methylviologen dication confined in magnetic hosts: synthesis, structural characterization, charge-transfer and magnetic properties of {(MV)2[Ni(SCN)5].Cl.2H2O}n and {(MV)[m(N3)2(SCN)2]}n (M=Mn, Co).

Three hybrid host-guest compounds {(MV)2[Ni(SCN)5].Cl.2H2O}n (1), {(MV)[Mn(N3)2(SCN)2]}n (2) and {(MV)[Co(N3)2(SCN)2}n (3) (where MV2+ = methylviologen dication) have been obtained by self-assembly methods and characterized by X-ray crystallography, spectral methods and magnetic measurements. Compound 1 shows a quasi-two-dimensional structure which is formed by novel single thiocyanate-bridged Ni(II) chains connected through S...S interactions. Compounds 2 and 3 are isostructural, containing single micro(1,3)-azide bridged Mn(II)/Co(II) square layers. MV2+, as a strong electron-acceptor and a template, is embedded between the anionic layers in all three compounds. The charge-transfer (CT) interactions between MV2+ and the anionic hosts have been revealed by structural analysis and UV-vis diffuse reflection spectroscopy. The magnetic studies of the compounds show antiferromagnetic interactions between adjacent metal ions (J = -34.52(7) cm(-1) for 1, J = -3.90(2) cm(-1) for 2 and J = -10.96(6) cm(-1) for 3).

A two-step field-induced magnetic transition in spin-canted systems observed only for the CoII coordination polymer.

Two isostructural 1D compounds {[M3(hpdc)2(H2O)6] 2H2O}n (M = Mn, Co; H3hpde = 2-hydroxypyrimidine-4,6-dicarboxylic acid) were synthesized by the in situ hydrothermal reactions of 2-chloropyrimidine-4,6-dicarboxylic acid with MCl2 (M = Mn, Co) and NaOH; the MnII compound shows spin-canted antiferromagnetism, whereas the CoII compound exhibits the coexistence of spin-canting and a two-step field-induced magnetic phase transition.

[Co5(mu3-OH)2(btec)2(bpp)]n: a three-dimensional homometallic molecular metamagnet built from the mixed hydroxide/carboxylate-bridged ferrimagnetic-like chains.

A three-dimensional homometallic complex [Co(5)(mu(3)-OH)(2)(btec)(2)(bpp)](n) is built from the mixed hydroxide/carboxylate bridged cobalt(ii) chains linked by the 1,2,4,5-benzenetetracarboxylate (btec(4-)) anion and 1,3-bis(4-pyridyl)-propane molecule (bpp). Within each chain, two mu(3)-OH-bridged metal triangles connect to each other by sharing a common vertex to give rise to a bow-tie type Co(5)(mu(3)-OH)(2) subunit, which is joined to adjacent subunits by four mu(1,1)-carboxylate bridges to form a step-like metal-oxygen backbone. The magnetic studies revealed that the coexistence of ferromagnetic and antiferrimagnetic interactions resulted in a ferrimagnetic-like behavior of the homometallic chains. Below a critical temperature (T(N) = 12.5 K), bulk antiferromagnetic ordering was observed at low field due to the weak interchain antiferromagnetic interactions. A metamagnetic transition occurred at a magnetic field of ca. 5 kOe at 2 K.

[FTIR studies of L-threonic acid and its metal compounds].

Highly pure solid compounds, such as L-threonic acid, calcium L-threonate, magnesium L-threonate, manganese L-threonate, cobalt L-threonate, nickel L-theronate, and zinc L-threonate, were prepared, wherein, L-threonic acid was obtained from calcium L-threonate by strong acid type ion exchange process, calcium L-threonate or zinc L-threonate was prepared by alcohol extracting the concentrated filter liquor of the reaction of Vc, H2O2 and CaCO3 or ZnCO3, the reminder of the compounds were synthesized using alcohol extracting the concentrated solution derived from the reaction of L-threonic acid solution, prepared by double decomposition reaction of calcium L-threonate with oxalic acid, and superfluous MgO, MnCO3, Co2(OH)2CO3 and Ni2(OH)2CO3. The compositions of the compounds were determined by chemical and elemental analysis, and these compounds have the formula M(C4H7O5)2.nH2O (M = Ca, Zn, n = 0; M = Mg, Mn, Co, n = 1; M = Ni, n = 2). The purity of the compounds was 99.60% by HPLC. The IR spectra of the complexes were similar with each other but different from that of L-threonic acid. The characteristic absorption peaks of water were not observed in those of calcium L-threonate or zinc L-threonate, which showed that the molecule of water was not involved in the complexes. Further analyses indicate that M2+ in the compounds coordinated to oxygen atom of the carboxy group, while the proton of the carboxyl group was dissociated and the proton belonging to hydroxyl was not M2+ coordinated to L-threonic acid through the sp3 hybrizated fashion. It was assumed that the coordination number of M2+ was 4.