Jian Lü

Coordination polymers based on flexible ditopic carboxylate or nitrogen-donor ligands

The design and construction of coordination polymers (CPs) is of current interest in the fields of supramolecular chemistry and crystal engineering. Compared to rigid ligands, using flexible ligands to construct CPs is more difficult and developing systematic methodologies of synthesis materials from a prior design structure via flexible ligands is still a great challenge. Due to the sensitivity and diversification of flexible ligands, they can afford good opportunities to investigate the details of the self-assembly process and provide more information on the directional synthesis of target CPs. We have long been involved in the area of flexible ligand complex design and synthesis. The guiding principle of this highlight attempts to represent structural features and influential factors which we have learned throughout the course of this research. Although a priori rigorous prediction and control of crystal structures is still difficult, we hope our observations can be useful for further research and make a step closer to understanding the mystery of self-assembly of CPs.

Analysis of High and Selective Uptake of CO2 in an Oxamide-Containing {Cu2(OOCR)4}-Based Metal–Organic Framework

The porous framework [Cu2(H2O)2L]⋅4u2009H2O⋅2u2009DMA (H4L = oxalylbis(azanediyl)diisophthalic acid; DMA = N,N-dimethylacetamide), denoted NOTT-125, is formed by connection of {Cu2(RCOO)4} paddlewheels with the isophthalate linkers in L(4-). A single crystal structure determination reveals that NOTT-125 crystallises in monoclinic unit cell with a = 27.9161(6), b = 18.6627(4) and c = 32.3643(8)u2005Å, β = 112.655(3)°, space group P2(1)/c. The structure of this material shows fof topology, which can be viewed as the packing of two types of cages (cageu2005A and cageu2005B) in three-dimensional space. Cageu2005A is constructed from twelve {Cu2(OOCR)4} paddlewheels and six linkers to form an ellipsoid-shaped cavity approximately 24.0u2005Å along its long axis and 9.6u2005Å across its central diameter. Cageu2005B consists of six {Cu2(OOCR)4} units and twelve linkers and has a spherical diameter of 12.7u2005Å taking into account the van der Waals radii of the atoms. NOTT-125 incorporates oxamide functionality within the pore walls, and this, combined with high porosity in desolvated NOTT-125a, is responsible for excellent CO2 uptake (40.1u2005wtu2009% at 273u2005K and 1u2005bar) and selectivity for CO2 over CH4 or N2. Grand canonical Monte Carlo (GCMC) simulations show excellent agreement with the experimental gas isotherm data, and a computational study of the specific interactions and binding energies of both CO2 and CH4 with the linkers in NOTT-125 reveals a set of strong interactions between CO2 and the oxamide motif that are not possible with a single amide.

Interpenetrated metal–organic frameworks of self-catenated four-connected mok nets

We describe two cobalt metal-organic frameworks built by amide derivative and organodicarboxyl co-ligands, displaying 3-fold interpenetration of 6(5).8-mok nets which are 4-connected self-catenated nets described theoretically in the early nineties.

Conformation control of a flexible 1,4-phenylenediacetate ligand in coordination complexes: a rigidity-modulated strategy

Five coordination complexes based on the flexible ligand 1,4-phenylenediacetic acid (H2pda), formulated as Zn(trans-pda) (1a), Mn(H2O)2(trans-pda) (1b), [M(cis-pda)(4,4′-bipy)]·H2O (M = Zn (2a), Co (2b), Cd (2c); H2pda = 1,4-phenylenediacetic acid; 4,4′-bipy = 4,4′-bipyridine), are reported. The crystal structures of the as-synthesized complexes were determined by single-crystal X-ray diffraction analyses. Complexes 1a and 1b have similar three-dimensional (3-D) network structures built by tetrahedral Zn nodes (for 1a) or octahedral Mn nodes (for 1b) and trans-pda2− bridges. Complexes 2a, 2b, and 2c possess similar two-dimensional (2-D) layered structures constructed from interconnecting metal-cis-pda2− double chains by 4,4′-bipy ligands. It is interesting that conformation of the flexible pda2− ligand is modulated in presence of the rigid 4,4′-bipy ligand. The trans-pda2− ligand was typically isolated in a single pda2− system whereas the cis-pda2− ligand was observed in a mixed pda2−/4,4′-bipy system. Furthermore, the dimensionalities of the complexes vary from 3-D (1a and 1b) to 2-D (2a, 2b, and 2c) when auxiliary 4,4′-bipy ligands were introduced. The photoluminescent studies on solid-state samples of complexes 1a, 2a and 2c indicate that the complexes exhibit intense fluorescent emissions at room temperature.

Copper 5-sulfoisophthalato quasi-planar squares in coordination polymers modulated by alkaline-earth metals: a way to molecular squares?

Two copper-sip coordination polymers (sip3− = 5-sulfoisophthalic anion), [Ca(H2O)3Cu2(H2O)6(sip)2]·2H2O 2a, and [Sr(H2O)4Cu2(H2O)6(sip)2]·H2O 2b, have been synthesized at room temperature. Single-crystal X-ray diffraction reveals that the structures of complexes 2a and 2b are 2-D coordination layer structures, containing [Cu4(sip)4] molecular squares linked by calcium (2a) or strontium (2b) bridges. The coordination layers display 3,6-connected topologies if the [Cu4(sip)4] molecular squares and alkaline-earth metals are considered as nodes, or (4,4) nets if alkaline-earth metals are considered to be part of the [Cu4(sip)4] squares. In comparison with the more commonly encountered Cu-sip zigzag chain subunits in copper-sip coordination polymers, the [Cu4(sip)4] square subunits in 2a and 2b represent similar coordination fashions and connecting modes while creating singular examples of new subunits in coordination complexes of the copper-sip system. Variable temperature magnetic susceptibility of 2a indicated that antiferromagnetic interactions dominate between the Cu(II) ions bridged by sip3− ligands.

Progressive release of a palladium-pyridyl complex from a layer-by-layer multilayer and illustrative application to catalytic Suzuki coupling

Quartz slides bearing layers of a palladium azopyridine complex are seen to liberate catalytic amounts of a soluble active palladium species which can be used for Suzuki coupling.

Photocatalytic properties of polyoxometalate–thionine composite films immobilized onto microspheres under sunlight irradiation

Multilayer films (PW12–TH)n (PW12 = PW12O403−, TH = thionine) were prepared on quartz slides and MnCO3 microspheres by an electrostatic layer-by-layer (LbL) self-assembly method. The composite films on quartz slides were characterized by UV-vis spectra and atomic force microscopy (AFM) images. MnCO3 microspheres coated with (PW12–TH)n composite films were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. The microspheres exhibited photocatalytic activity for methyl orange (MO) under sunlight irradiation. Compared with the (PW12–TH)10 composite films on quartz slides, the microspheres showed a higher photoactivity due to the increase of the specific surface area. The photocatalytic properties of the microspheres toward a rhodamine B (RhB) solution were also investigated. The results indicated that the decrease of the absorbance was due to the destruction of the dye chromophore. The kinetics of the photodecomposition follows the first-order reaction. The dye molecule TH of the composite films is excited by sunlight irradiation to the appropriate excited states. Then, the electron injection into the conduction band of polyoxometalates (POMs) follows and results in the photodegradation of the target dye molecules.

An efficient and reusable silica/dendrimer supported platinum catalyst for electron transfer reactions

A series of Pt nanoparticles (NPs) smaller than 3 nm were successfully encapsulated in dendrimer/SBA-15 organic and inorganic hybrid composite. The obtained catalysts were characterized by XPS, XRD and TEM. The results of XPS and XRD indicate the existence of Pt NPs in the hybrid matrix. TEM images display the Pt NPs with narrow size distribution are monodispersed in SBA-15 channels. Catalytic property of the supported Pt catalysts was investigated in inorganic (ferricyanide to ferrocyanide by thiosulfate) and organic (p-nitrophenol to p-aminophenol by sodium borohydride) electron transfer (redox) reactions. In both cases, the reduction reactions followed smoothly and the catalysts showed excellent catalytic activity. Moreover, the catalysts can be easily separated and reused several times preserving good catalytic performance.

In situ synthesis of Ag nanoparticles in aminocalix[4]arene multilayers.

The layer-by-layer (LbL) assembled thin films containing tetraamino-thiacalix[4]arenes (1) and tetraamino-calix[4]arenes (2) were used as nanoreactor to synthesize in situ Ag nanoparticles (Ag NPs). UV-vis spectra and AFM images demonstrate that Ag NPs are included in the (1/Ag NPs)(n) and (2/Ag NPs)(n) multilayer films. The silver ions are absorbed through cation-pi interaction and calix[4]arene-metal ion coordination interaction and are reduced into Ag NPs by calix[4]arenes. TEM images indicated that Ag NPs within aminocalix[4]arene multilayers were highly dispersed and uniform. Moreover, the mean size of Ag NPs is smaller than 10 nm.

Cobalt-cluster-based coordination polymers with size-matching mixed ligands

A series of mixed ligand cobalt coordination polymers built by V-shaped O-donor ligand and linear N-donor ligand, namely [Co(BPE)(L)] (1), [Co3(BPE)2(HL)2(L)2] (2), and [Co5(BPE)2(OH)2(L)4]·4DMA (3) (H2L = 4,4′-(hexafluoroisopropylidene)-bis(benzoic acid), BPE = 1,2-di(4-pyridyl)ethane, DMA = dimethylacetamide), was synthesized under hydrothermal/solvothermal conditions. Compound 1 displays a two-dimensional (2-D) double layer structure of {Co2} clusters bridged by BPE and L2− ligands. Compounds 2 and 3 exhibit three-dimensional (3-D) networks built by {Co3} (2) and {Co5} (3) clusters, respectively, interconnected by BPE and L2− ligands. Topological analysis indicates compound 2 has a doubly interpenetrated (412·63)-pcu (α-Po, 6-connected) network, whereas compound 3 possesses an 8-connected (36·418·53·6)-hex network. It has been found that the reaction media and reaction conditions play key roles for the formation of cobalt clusters in the self-assemblies of compounds 1–3.