Monolayer Nanosheets Exfoliated from Cage-Based Cationic Metal-Organic Frameworks.

The rational design and preparation of monolayer metal-organic framework (MOF) nanosheets remain great challenges. Recently, we found that monolayer MOF nanosheets can be facially exfoliated on a large scale from pristine two-dimensional (2D) MOFs with substantially reduced interlaminar interaction. By employing cage-like bicyclocalix[2]arene[2]triazine tri-imidazole as the building block, a family of cationic two-dimensional metal-organic frameworks (2D MOFs) with steric layer were designed and prepared. The single crystal structures have clearly identified that only very weak and sparse distributed C-H···π interaction exists between adjacent layers.On the basis of density functional theory calculation, the interlayer interaction of these cage-based cationic 2D MOFs was estimated to be 1/46th of that of graphite. Due to the extremely weak interaction, these cationic 2D MOFs tend to degenerate into an "amorphous" state after being soaked in other solvents; they can be readily exfoliated into 1.1 nm thick monolayer nanosheets with a high degree of thickness homogeneity, large lateral size, and significantly enlarged surface area. This work has identified that a cage-like molecule is the ideal building block for 2D cationic MOFs and ultrathin nanosheets; It was futher confirmed that weakening the interlaminar interaction is an effective strategy for facilely producing monolayer nanosheets.

Co(II)-MOF: A Highly Efficient Organic Oxidation Catalyst with Open Metal Sites.

A porous Co(II)-MOF (1) was synthesized by the combination of a bent imidazole-bridged ligand and p-phthalic acid (PTA) with Co(OAc)2 under solvothermal conditions. This Co(II)-MOF (1) is able to undergo a reversible MeOH substitution reaction on the Co(II) center via a single-crystal-to-single-crystal process. The desolvated Co(II)-MOF (2) with the open Co(II) sites is very stable (up to 350 °C). Furthermore, 2 is a highly active heterogeneous catalyst for various organic substrates oxidation in the presence of tert-butyl hydroperoxide (TBHP) under milder conditions. The importance of open Co(II) sites in 2 for the organic substrates oxidation is directly evidenced by the single-crystal X-ray diffraction.

Copper(I) Metal-Organic Framework: Visual Sensor for Detecting Small Polar Aliphatic Volatile Organic Compounds.

A porous Cu(I)-MOF [H2O⊂Cu2(L)2I2; L = 1-benzimidazolyl-3,5-bis(4-pyridyl)benzene], which can be a visual and luminescent sensor for detecting small polar aliphatic volatile organic compounds (VOCs), such as alcohols, ketones, and halocarbons, is reported. The naked-eye and luminescent detection limitations for these VOCs are 5 and 1 ppm, respectively.

Visual synchronous exchange of metal nodes and counteranions constituting a cobalt(II) coordination polymer.

A solid-state simultaneous exchange of metal nodes and counteranions based on a cobalt(2+) coordination polymer is reported for the first time. The ion-exchange process is visual, and the structural integrity of the cobalt(2+) coordination polymer is maintained during the ion-exchange process.

Cd(II)-MOF: adsorption, separation, and guest-dependent luminescence for monohalobenzenes.

A series of isostructural 2-fold interpenetrating 2D Cd(II)-MOFs, namely G⊂CdL2(OTs)2 (G = THF (1), PhF (2), PhCl (3), PhBr (4), PhI (5), L = 1,2-bis[(3-(pyridin-4-yl)phenoxy]ethane, and OTs(-) = p-toluenesulfonate anion), have been successfully synthesized from the flexible ethylene glycol ether-bridging ligand L and Cd(OTs)2 in solution. The CdL2(OTs)2 framework contains squarelike nonpolar channels, and the encapsulated guest molecules can be removed by heating (150 °C) to generate a guest-free host framework which is able to reversibly adsorb monohalobenzenes PhX (X = F, Cl, Br, I) in the liquid phase under ambient conditions without loss of framework integrity. Furthermore, it can effectively separate these monohalobenzenes and exhibits a clear affinity for monohalobenzenes according to the following order: PhI > PhBr > PhCl > PhF. In addition, PhX⊂CdL2(OTs)2 exhibits guest-dependent luminescence properties.

Cd(II)-coordination framework: synthesis, anion-induced structural transformation, anion-responsive luminescence, and anion separation.

A series of Cd(II) coordination frameworks that are constructed from a new oxadiazole-bridged ligand 3,5-bis(3-pyridyl-3-(3'-methylphenyl)-1,3,4-oxadiazole (L) and CdX2 (X = NO3(-), Cl(-), Br(-), I(-), N3(-), and SCN(-)) were synthesized. The NO3(-) anion of the solid CdL2(NO3)2·2THF (1) is able to be quantitatively exchanged with Cl(-), Br(-), I(-), SCN(-), and N3(-) in the solid state. For Cl(-) and Br(-), the anion exchange resulted in a anion-induced structural transformation to form the structures of 2 and 3, respectively. In addition, the Cd(II) structure herein exhibits the anion-responsive photoluminescence, which could be a useful method to monitor the anion-exchange process. Notably, compound 1 can recognize and completely separate SCN(-)/N3(-) with similar geometry.

Three isomorphous two-dimensional coordination polymers generated from a benzimidazole bridging ligand and ZnX2 (X = Cl, Br and I).

A novel bridging asymmetric benzimidazole ligand, 4-{2-[3-(pyridin-4-yl)phenyl]-1H-benzimidazol-1-ylmethyl}benzoic acid, was used to construct three isomorphous two-dimensional coordination polymers, namely catena-poly[chlorido(µ3-4-{2-[3-(pyridin-4-yl)phenyl]-1H-benzimidazol-1-ylmethyl}benzoato)zinc(II)], [Zn(C26H18N3O2)Cl]n, (I), and the bromide, (II), and iodide, (III), analogues. Neighbouring two-dimensional networks are stacked into three-dimensional frameworks via interlayer π-π interactions. The luminescent properties of (I)-(III) were investigated and they display an obvious red-shift in the solid state at room temperature.

Zn(II) and Cu(II) complexes generated from 5-(pyridin-4-yl)-3-[2-(pyridin-4-yl)ethyl]-1,3,4-oxadiazole-2(3H)-thione.

A new 1,3,4-oxadiazole-containing bispyridyl ligand, namely 5-(pyridin-4-yl)-3-[2-(pyridin-4-yl)ethyl]-1,3,4-oxadiazole-2(3H)-thione (L), has been used to create the novel complexes tetranitratobis{µ-5-(pyridin-4-yl)-3-[2-(pyridin-4-yl)ethyl]-1,3,4-oxadiazole-2(3H)-thione}zinc(II), [Zn2(NO3)4(C14H12N4OS)2], (I), and catena-poly[[[dinitratocopper(II)]-bis{µ-5-(pyridin-4-yl)-3-[2-(pyridin-4-yl)ethyl]-1,3,4-oxadiazole-2(3H)-thione}] nitrate acetonitrile sesquisolvate dichloromethane sesquisolvate], {[Cu(NO3)(C14H12N4OS)2]NO3·1.5CH3CN·1.5CH2Cl2}n, (II). Compound (I) presents a distorted rectangular centrosymmetric Zn2L2 ring (dimensions 9.56 × 7.06 Å), where each Zn(II) centre lies in a {ZnN2O4} coordination environment. These binuclear zinc metallocycles are linked into a two-dimensional network through nonclassical C-H···O hydrogen bonds. The resulting sheets lie parallel to the ac plane. Compound (II), which crystallizes as a nonmerohedral twin, is a coordination polymer with double chains of Cu(II) centres linked by bridging L ligands, propagating parallel to the crystallographic a axis. The Cu(II) centres adopt a distorted square-pyramidal CuN4O coordination environment with apical O atoms. The chains in (II) are interlinked via two kinds of π-π stacking interactions along [0-11]. In addition, the structure of (II) contains channels parallel to the crystallographic a direction. The guest components in these channels consist of dichloromethane and acetonitrile solvent molecules and uncoordinated nitrate anions.

Two one-dimensional coordination polymers generated from a new benzimidazole bridging ligand and CdX2 (X = Br and I).

The novel asymmetric bridging ligand 1-[(pyridin-3-yl)methyl]-2-[4-(pyridin-3-yl)phenyl]-1H-benzimidazole (L) has been used to construct the coordination polymers catena-poly[[[dibromidocadmium(II)]-µ3-1-[(pyridin-3-yl)methyl]-2-[4-(pyridin-3-yl)phenyl]-1H-benzimidazole] monohydrate], {[CdBr2(C24H18N4)]·H2O}n, (I), and catena-poly[[diiodidocadmium(II)]-µ3-1-[(pyridin-3-yl)methyl]-2-[4-(pyridin-3-yl)phenyl]-1H-benzimidazole], [CdI2(C24H18N4)]n, (II). Compounds (I) and (II) are closely related one-dimensional polymers based on 16- and 20-membered macrocycles along the chains, but they are not isomorphous. The chains are crosslinked into a two-dimensional network via hydrogen bonds and π-π interactions in (I), and into a three-dimensional framework through π-π interactions in (II). One well-ordered solvent water molecule per asymmetric unit is included in (I) and forms O···Br hydrogen bonds.

The coordination chemistry of two symmetric fluorene-based organic ligands with cuprous chloride.

Two novel symmetric fluorene-based ligands, namely, 2,7-bis(1H-imidazol-1-yl)-9,9-dimethyl-9H-fluorene [L1 or (I), C21H18N4] and 2,7-bis(1H-imidazol-1-yl)-9,9-dipropyl-9H-fluorene (L2), have been used to construct the coordination polymers catena-poly[[dichloridodicopper(I)(Cu-Cu)]-µ-2,7-bis(1H-imidazol-1-yl)-9,9-dimethyl-9H-fluorene], [Cu2Cl2(C21H18N4)]n, (II), and catena-poly[[tetra-µ2-chlorido-tetracopper(I)]-bis[µ-2,7-bis(1H-imidazol-1-yl)-9,9-dipropyl-9H-fluorene]], [Cu4Cl4(C25H26N4)2]n, (III). There are three types of C-H···N hydrogen bonds in (I), resulting a two-dimensional network in the ab plane, including a chiral helical chain along the b axis. Compounds (II) and (III) are related one-dimensional polymers. In both, Cu(I) atoms connect the symmetric ligands (L1 or L2) into a one-dimensional chain. In (II), the {[Cu(I)Cl2](-)} unit, acting as a co-anion, adheres to the one-dimensional chain through a weak Cu···Cu interaction. However, in (III), the {[Cu(I)2Cl4](2-)} unit links two different chains into a one-dimensional rope-ladder-type chain. In addition, there are C-H···Cl hydrogen bonds and π-π interactions in the extended structures of (II) and (III), the difference is that the chains in (II) are linked into a two-dimensional network while the chains in (III) are stacked into a three-dimensional framework.

A well-resolved cyclic water tetramer in a dinuclear CuII coordination complex based on 1,2-bis(pyridin-3-yloxy)ethane and capped by pyridine-2,6-dicarboxylic acid.

µ-1,2-Bis(pyridin-3-yloxy)ethane-κ(2)N:N'-bis[aqua(pyridine-2,6-dicarboxylato-κ(3)O(2),N,O(6))copper(II)] tetrahydrate, [Cu2(C7H3NO4)2(C12H12N2O2)(H2O)2]·4H2O, (I), is a C-shaped molecule based on 1,2-bis(pyridin-3-yloxy)ethane (L) and Cu(II) in the presence of pyridine-2,6-dicarboxylic acid (H2pydc). The two five-coordinated Cu(II) centres are chelated by terminal pydc(2-) ligands and bridged by an L spacer. The molecules are arranged in a two-dimensional sheet via 15 O-H...O hydrogen bonds, and C-H...O interactions further bridge neighbouring sheets into a three-dimensional supermolecular architecture. The structure includes a well-resolved cyclic water tetramer, which acts as a subunit to form a larger aggregate. A thermogravimetric analysis of complex (I) was also carried out.

2,5-Bis[4-methyl-3-(pyridin-3-yl)phenyl]-1,3,4-oxadiazole and its one-dimensional polymeric complex with ZnCl2.

2,5-Bis[4-methyl-3-(pyridin-3-yl)phenyl]-1,3,4-oxadiazole (L), C26H20N4O, forms one-dimensional chains via two types of intermolecular π-π interactions. In catena-poly[[dichloridozinc(II)]-µ-2,5-bis[4-methyl-3-(pyridin-3-yl)phenyl]-1,3,4-oxadiazole], [ZnCl2(C26H20N4O)]n, synthesized by the combination of L with ZnCl2, the Zn(II) centres are coordinated by two Cl atoms and two N atoms from two L ligands. [ZnCl2L]n forms one-dimensional P (plus) and M (minus) helical chains, where the L ligand has different directions of twist. The helical chains stack together via interchain π-π and C-H···π interactions.

Independent 1D nanosized metal-organic tube: anion exchange, separation, and anion-responsive luminescence.

Three independent 1D metal-organic nanotubes AgL(2)X(2) [X = PF(6)(-) (1), ClO(4)(-) (2), and SbF(6)(-) (3)] with anion exchange, separation, and anion-responsive photoluminescence are reported.

Encapsulation and sensitization of UV-vis and near infrared lanthanide hydrate emitters for dual- and bimodal-emissions in both air and aqueous media based on a porous heteroatom-rich Cd(II)-framework.

A porous heteroatom-rich Cd(II)-polymeric framework which is generated from an ethylene glycol ether-bridging dicarboxylate ligand L, 4,4'-bipy and Cd(II) ion is reported. It contains one-dimensional tubes (9-11 Å) which are able to trap cationic lanthanide hydrates such as Eu(H(2)O)(8)(3+), Tb(H(2)O)(8)(3+), and Nd(H(2)O)(8)(3+) under ambient conditions to generate Ln(H(2)O)(8)(3+)-loaded materials. In addition, the heteroatom-rich host material can effectively protect and sensitize the encapsulated Ln(3+) emitters in their hydrate form in both air and aqueous media. Furthermore, the dual- and bimodal-emissions are successfully realized by intercalation of the different Ln(3+)-hydrates based on a guest-driven approach.

One-dimensional coordination polymers generated from a new triazole bridging ligand and HgX2 (X = Cl, Br and I): characterization and luminescent properties.

The new 4-amino-1,2,4-triazole asymmetric bridging ligand 4-amino-5-(pyridin-3-yl)-3-[4-(pyridin-4-yl)phenyl]-4H-1,2,4-triazole (L) has been used to generate three novel isomorphic one-dimensional coordination polymers, viz. catena-poly[[tris[dichloridomercury(II)]-bis{µ(3)-4-amino-5-(pyridin-3-yl)-3-[4-(pyridin-4-yl)phenyl]-4H-1,2,4-triazole}] acetonitrile monosolvate], {[Hg(3)Cl(6)(C(18)H(14)N(6))(2)]·CH(3)CN}(n), (I), and the bromido, {[Hg(3)Br(6)(C(18)H(14)N(6))(2)]·CH(3)CN}(n), (II), and iodido, {[Hg(3)I(6)(C(18)H(14)N(6))(2)]·CH(3)CN}(n), (III), analogs. The asymmetric ligand acts as a tridentate ligand to coordinate the three different Hg(II) centers (two of which are symmetry-related). Two ligands and two symmetry-related Hg(II) centers form centrosymmetric rectangular units which are linked into one-dimensional chains via the other unique Hg atoms, which sit on mirror planes. The chains are elaborated into a three-dimensional structure via interchain hydrogen bonds. The acetonitrile solvent molecules are located in ellipsoidal cavities. The luminescent character of these three coordination complexes was investigated in the solid state.

3,5-Bis{4-[(benzimidazol-1-yl)methyl]phenyl}-4H-1,2,4-triazol-4-amine and its one-dimensional polymeric complex with HgCl2.

The molecule of 3,5-bis{4-[(benzimidazol-1-yl)methyl]phenyl}-4H-1,2,4-triazol-4-amine (L), C(30)H(24)N(8), has an antiperiplanar conformation of the two terminal benzimidazole groups and forms two-dimensional networks along the crystallographic b axis via two types of intermolecular hydrogen bonds. However, in catena-poly[[[dichloridomercury(II)]-µ-3,5-bis{4-[(benzimidazol-1-yl)methyl]phenyl}-4H-1,2,4-triazol-4-amine] dichloromethane hemisolvate], {[HgCl(2)(C(30)H(24)N(8))]·0.5CH(2)Cl(2)}(n), synthesized by the combination of L with HgCl(2), the L ligand adopts a synperiplanar conformation. The Hg(II) cation lies in a distorted tetrahedral environment, which is defined by two N atoms and two Cl atoms to form a one-dimensional zigzag chain. These zigzag chains stack via hydrogen bonds which expand the dimensionality of the structure from one to two.

The structures of three Hg2X4L2 macrocycles {X = Cl, Br and I, and L = 1,2-bis[4-(pyridin-3-yl)phenoxy]ethane} assembled from ether-bridged dipyridyl ligands.

The new ether-bridged dipyridyl ligand 1,2-bis[4-(pyridin-3-yl)phenoxy]ethane (L) has been used to synthesize three isostructural centrosymmetric binuclear Hg(II) macrocycles, namely bis{µ-1,2-bis[4-(pyridin-3-yl)phenoxy]ethane-κ(2)N:N'}bis[dichloridomercury(II)], [Hg(2)Cl(4)(C(24)H(20)N(2)O(2))(2)], and the bromido, [Hg(2)Br(4)(C(24)H(20)N(2)O(2))(2)], and iodido, [Hg(2)I(4)(C(24)H(20)N(2)O(2))(2)], analogues. The Hg atoms adopt a highly distorted tetrahedral coordination environment consisting of two halides and two pyridine N-donor atoms from two bridging ligands. In the solid state, the macrocycles form two-dimensional sheets in the bc plane through noncovalent Hg...X and X...X (X = Cl, Br and I) interactions.

5,17-Dibromo-26,28-bis-[(meth-oxy-carbon-yl)meth-oxy]-25,27-diprop-oxy-2,8,14,20-tetra-thia-calix[4]arene.

The title thia-calix[4]arene derivative, C(36)H(34)Br(2)O(8)S(4), adopts an unusual pinched cone conformation with the prop-oxy-substituted benzene rings inclined inward [forming a dihedral angle of 33.4 (1)°] and with the brominated benzene rings bent outward, making a dihedral angle of 66.1 (1)°. In the crystal, the mol-ecules form chains along [001] via C-H⋯S hydrogen bonds and S⋯S contacts [S⋯S = 3.492 (3) Å]. The chains are associated into bilayers through C-H⋯O hydrogen bonds, generating an R(2) (2)(10) motif.

Two threefold interpenetrated two-dimensional frameworks based on a flexible imidazole-containing ligand and benzene-1,4-dicarboxylate.

The open-chain polyether-bridged flexible ligand 1,2-bis[2-(1H-1,3-imidazol-1-ylmethyl)phenoxy]ethane (L) has been used to create two two-dimensional coordination polymers under hydrothermal reaction of L with Cd(II) or Co(II), in the presence of benzene-1,4-dicarboxylic acid (H(2)bdc). In poly[[(µ(2)-benzene-1,4-dicarboxylato){µ-1,2-bis[2-(1H-1,3-imidazol-1-ylmethyl)phenoxy]ethane}cadmium(II)] dihydrate], {[Cd(C(8)H(4)O(4))(C(22)H(22)N(4)O(2))]·2H(2)O}(n), (I), and the cobalt(II) analogue {[Co(C(8)H(4)O(4))(C(22)H(22)N(4)O(2))]·2H(2)O}(n), (II), the Cd(II) and Co(II) cations are six-coordinated by four carboxylate O atoms from two different bdc(2-) dianions in a chelating mode and two N atoms from two distinct L ligands. The metal ions, bdc(2-) dianions and L ligands each sit across crystallographic twofold axes. The bdc(2-) coordination mode and the coordinating orientation of the L ligand play an important role in constructing the novel two-dimensional framework. Complexes (I) and (II) are threefold interpenetrated two-dimensional frameworks; their structures are almost isomorphous, while the bond lengths, angles and hydrogen bonds are different in (I) and (II).

Supramolecular structures constructed by 3-(2-amino-6-chloropyrimidin-4-yl)-1,1-dimethylprop-2-yn-1-ol monohydrate and 3-[2-amino-6-(3-hydroxy-3,3-dimethylprop-1-yn-1-yl)pyrimidin-4-yl]-1,1-dimethylprop-2-yn-1-ol.

The molecule of 3-(2-amino-6-chloropyrimidin-4-yl)-1,1-dimethylprop-2-yn-1-ol monohydrate, C(9)H(10)ClN(3)O·H(2)O, (I), shows a very polarized molecular-electronic structure, while the polarization is slight for 3-[2-amino-6-(3-hydroxy-3,3-dimethylprop-1-yn-1-yl)pyrimidin-4-yl]-1,1-dimethylprop-2-yn-1-ol, C(14)H(17)N(3)O(2), (II). In the supramolecular structure of (I), a combination of hard N-H···N hydrogen bonds and soft C-H···N hydrogen bonds creates a molecular column. Aromatic π-π stackings between the pyrimidine rings stabilize the column with perpendicular and centroid-centroid distances of 3.283 (3) and 3.588 (1) Å, respectively. Short Cl···Cl contacts further link neighbouring molecular columns, creating a hydrophilic tube in which water molecules are fixed by various hydrogen bonds. In the packing of (II), a one-dimensional molecular chain is formed through several contacts involving hard N-H···O(N) and O-H···O(N) and soft C-H···O hydrogen bonds. Interchain O-H···O hydrogen bonds link the chains giving a two-dimensional stepped network. It is anticipated that study of the influence of hydrogen bonding on the patterns of base pairing and molecular packing in aminopyrimidine structures will shed significant light on nucleic acid structures as well as their functions.