Guang-Sheng Yang

Chiral Nanoporous Metal‐Organic Frameworks with High Porosity as Materials for Drug Delivery

A chiral nanoporous metal-organic framework (MOF) with high porosity is obtained based on nontoxic zinc and achiral hexadentate ligand. It shows high drug loading and slow release of the proportion of the loaded drug with a complete delivery time of about one week when used as a material for adsorption and delivery of anticancer 5-fluorouracil.

Construction and property investigation of transition-metal complexes modified octamolybdate hybrid materials based on V-shaped organic ligands

Six new transition-metal complexes modified octamolybdate compounds have been successfully synthesized with two kinds of V-shaped flexible organic ligands under hydrothermal conditions, namely, [CuII(HL1)2(H2O)2(Mo8O26)] (1), [CuII(L1)2(Mo8O26)0.5] (2), [CuII(HL2)2(Mo8O26)]·2H2O (3), [CuII2(L2)4(Mo8O26)]·3H2O (4), [CuI3(L2)2(Mo8O26)0.5Cl] (5), [CuI4(L2)4(Mo8O26)] (6) where L1 = 3-((1H-imidazol-1-yl)methyl)pyridine, L2 = 3-((1H-1,2,4-triazol-1-yl)methyl)pyridine. Their crystal structures have been determined by X-ray single-crystal diffraction, elemental analyses, IR spectra, and thermogravimetric analyses (TGA). With L1 ligand, two compounds were obtained: compound 1 is a 1D β-octamolybdate based chain and compound 2 is a 2D 4-connected network most strikingly, whose octamolybdate anion shows a θ-isomer. With L2 ligand, compounds 3, 4, 5 and 6 were obtained, respectively. In compound 3, 1D β-octamolybdate-based metal–organic chains are further extended by hydrogen bonds to build a 3D supramolecular structure, while in compound 4, every two adjacent double-helical metal–organic chains are bridged by β-octamolybdate anions to generate a 2D 3-connected network. When CuSO4·5H2O was substituted by CuCl, two CuI compounds were attained. Interestingly, in compound 5 the octamolybdate anion threads through the metal–organic loop presenting a fascinating 2D polythreading topology, and in compound 6 the octamolybdate anions pillar the railroad-like metal–organic strands to generate a 2D 3-connected network. The structural differences among compounds 1–6 indicate the importance of the different coordination mode of organic ligands and various polyoxoanions, and of the pH values of the systems for the framework formation. Furthermore, the semiconducting properties of compounds 1–5 were investigated, and photoluminescence as well as photoconductivity for compound 5 were also studied. Compound 5 has a comparatively lower band gap and is photoconductive in the UV-vis range, so it can be potentially applied as a semiconductor of photoelectronic detectors.

Two eight-connected self-penetrating porous metal–organic frameworks: configurational isomers caused by different linking modes between terephthalate and binuclear nickel building units

Two novel nanoporous metal–organic frameworks (MOFs) based on the same binuclear nickel secondary building units, {[Ni2(H2O)(BDC)2(BIMB)2]·6DMF}n (1) and {[Ni2(H2O)(BDC)2(BIMB)2]·5DMAc}n (2) (H2BDC = terephthalic acid, BIMB = 1,4-bis(1-imidazolyl)benzene and DMF = N,N′-dimethylformamide, DMAc = N,N′-dimethylacetamide) have been synthesized by self-assembly of Ni(NO3)2·6H2O, BIMB and H2BDC in different solvents (DMF and DMAc), respectively. Different linking modes between terephthalate and binuclear nickel building units in 1 and 2 lead to an interesting phenomenon that their host frameworks are isomeric to each other and have the same three periodic eight-connected self-penetrating nets with novel 420.68 topology. Powder X-ray diffraction (PXRD) results indicate that 1 and 2 both have reversible framework transformations in an acetone/guest solvent molecule system.

pH-dependent self-assembly of divalent metals with a new ligand containing polycarboxylate: syntheses, crystal structures, luminescent and magnetic properties

Six new coordination polymers, namely, [Cd(HL)(4,4′-bpy)(H2O)]·H2O (1), [Cd3(L)2(4,4′-bpy)3(H2O)]·2.5H2O (2), [Co(HL)(4,4′-bpy)]·H2O (3), [Co2(L)(4,4′-bpy)0.5(μ3-OH)(H2O)2]·H2O (4), [Zn(HL)(BIMB)]·2H2O (5), [Zn3(L)2(BIMB)2]·3H2O (6), where H3L = 5-(4-carboxybenzyloxy)isophthalic acid, 4,4′-bpy = 4,4′-bipyridine, BIMB = 1,4-di(1H-imidazol-1-yl)benzene, have been synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction. In complexes 1, 3 and 5, H3L ligand is partially deprotonated in the form of HL2−; while in 2, 4 and 6, it is completely deprotonated due to the influence of different pH values. Complexes 1 and 5 are 2D layer structures, the hydrogen bonds between lattice-water molecules and carboxylate groups of HL2− ligands extend the 2D layer into a 3D framework; while complex 3 is a 3D framework with α-Po topology. Complex 2 is a 3D fourfold interpenetrating (3,4,4)-connected net with (63)(62·84)(64·82) topology. Complex 4 is a twofold interpenetrating (3,8)-connected net with (43)2(46·618·84) topology. And complex 6 is a twofold interpenetrating (3,4,6)-connected net with (4·62)(64·72)(42·66·74·8·92) topology. In addition, powder X-ray diffraction and thermogravimetric analyses for 1–6, photoluminescent properties for 1, 2, 5, 6 and magnetic properties for 3, 4 are investigated in detail.

Remarkable solvent-size effects in constructing novel porous 1,3,5-benzenetricarboxylate metal–organic frameworks

Seven novel porous metal–organic frameworks (MOFs), Zn2(BTC)(NO3)(DMA)3 (1), Zn11(BTC)6(NO3)4(DEE)9 (2), Zn11(BTC)6(NO3)4(DEP)8 (3), Zn(BTC)·DMA·C2H8N (4), Zn3(BTC)3·3(C2H8N)·4(DMA) (5), Zn9(BTC)6(OH)2·2(C2H8N)·15(DEE) (6), and Zn9(BTC)5(OH)3(C2O4)·2(C4H12N)·5(DEE) (7) have been solvothermally synthesized using zinc nitrate, 1,3,5-benzenetricarboxylate acid (H3BTC) and differently sized solvents (DMF, DMA, DEE, DEP, DPE, DPP), showing that the solvent size can not only dramatically influence the pore size, but also allow access to new structures and topologies previously unrealized in MOFs. With increasing solvent size, the pore size of MOFs correspondingly changes from 9 A to 23 A along with different structures: three frameworks have cages larger than 16 A, one has a 23 A chiral cage, five are anionic frameworks, three have topologies heretofore unreported in MOFs and all structures are noninterpenetrating. The ion-exchange experiment estimated by HNMR analyses shows that dimethylamine ions in 5 can be exchanged by NH4+ ions.

Controllable synthesis of microporous, nanotubular and mesocage-like metal–organic frameworks by adjusting the reactant ratio and modulated luminescence properties of Alq3@MOF composites

Three metal–organic frameworks (MOFs) comprising micropore, mesocage and nanotube structures have been prepared based on the same ligands and binuclear zinc secondary building units. We have successfully achieved flexible modulation of pore size from micropore to mesopore in a binary system by adjusting the reactant ratio. With the merit of a nanoscale channel, IFMC-8 can be applied as the host material for encapsulating Alq3 chromophores to exhibit tunable luminescence. The fluorescence emission of composite material Alq3@IFMC-8 has changed from green to blue. More importantly, the inclusion of IFMC-8 effectively prolonged the excited-state lifetime of Alq3 in ethanol. To the best of our knowledge, it is the first time that a MOF was studied as the host material for modulating the fluorescence properties of Alq3 chromophores.

Synthesis and characterization of two {Mo6}-based/templated metal–organic frameworks

Here, we report two novel POM-based MOFs: a nano-caged hybrid compound [Ni2(BIMB)2(MoVI4MoV2O19)] (1), whose cages are based on [Mo6O19]4− units and a [Mo6O19]2−-templated framework [Zn4(BIMB)4(PO4)2(Mo6O19)]·2H2O (2) (BIMB = 1,4-bis(1-imidazolyl)benzene). According to topological analysis, the first is a 3D (4,6)-connected self-penetrating framework with polycatenanes motif. In contrast, the second metal–organic framework has no interpenetration for the templated [Mo6O19]2− occupying the cavity. The UV-vis absorption spectrum of 1 was investigated to prove the existence of MoV atoms and the typical peak at 577 nm can be attributed to MoV → MoVI charge transfer. Furthermore, the diffuse reflectivity spectrum shows that its band gap can be assessed as 3.06 eV, which can be regarded as a wide gap semiconductor. Additionally, cyclic voltammogram of compound 1 shows two redox peaks in the range of 0–800 mV in H2SO4 aqueous solution.

Inorganic-organic hybrid compounds based on the co-existence of different isomers or forms of polymolybdate†

Three novel compounds co-existing isomers or forms of polymolybdate, namely, {[Ni(γ-Mo8O26)(H2L1)2(H2O)2](γ-Mo8O26)(H2L1)}·2H2O (1), {[Co(γ-Mo8O26)(H2L1)2(H2O)2](β-Mo8O26)[Co(H2O)6]}·6H2O (2) and [CuI6L24(β-Mo8O26)(Mo6O19)] (3), where L1 = 1,1′-bis(pyridin-3-ylmethyl)-2,2′-biimidazole, L2 = 3-((1H-1,2,4-triazol-1-yl)methyl)pyridine, have been successfully synthesized. Crystal structure analysis reveals that 1 is a 1D + 1D supramolecular structure containing both γ-[Mo8O26N2] and γ-[Mo8O28] units; 2 has γ-[Mo8O26]4− as well as β-[Mo8O26]4− anions and 3 is a (3,4,6)-connected 2D network containing both β-[Mo8O26]4− and [Mo6O19]2− anions. According to quantum chemical calculations, the transformation from β-[Mo8O26]4− to [Mo6O19]2− is spontaneous in aqueous solution. Furthermore, we have investigated the optical band gap of compounds 1 and 3, with 3 showing a lower band gap (1.69 eV). Additionally, the photoluminescent property of 3 is also studied, which can be assigned to metal-to-ligand charge transfer (MLCT).

pH variation induced construction of a series of entangled frameworks based on bi- and tri-metallic cores as nodes

Reactions of 1,4-bis(pyridin-4-ylmethoxy)benzene (L) and zinc acetate salts with different multi-caboxylate acids: 1,4-benzenedicarboxylic (p-H2BDC), isophthalic acid (m-H2BDC) and benzene-1,3,5-tricarboxylic acid (H3BTC) yield four entangled structures and one 3D supramolecular framework depending on pH variation. The structures of compounds 1–5 were elucidated by single crystal X-ray diffraction. Topology analysis revealed that the entangled structures of compounds 1–4 covered a range of poly-threading, self-penetrating and interpenetrating coordination. Interestingly, the poly-threaded arrays with cyclohexane-like windows in chair conformation in compound 2 was firstly observed. Whats more, compound 4 exhibited a rare eight-connected self-penetrating network based on trinuclear zinc clusters as nodes with 42464 topology. Photoluminescent properties and thermogravimetric analyses for 1–5, were also investigated in detail.

pH-induced different crystalline behaviors in extended metal–organic frameworks based on the same reactants

pH-induced different crystalline behaviors based on the same reactants and reaction conditions are illustrated by our present study. Compound has been used for the adsorption and delivery of 5-FU.