Yue-Peng Cai

Single-crystal-to-single-crystal transformation in a one-dimensional Ag-Eu helical system.

Single-crystal-to-single-crystal transformation of one-dimensional 4d-4f coordination polymers has been investigated for the first time. More importantly, we observed the transformation of a meso-helical chain to a rac-helical chain as a function of the temperature.

Metal-directed assembly of two 2-D 4d–4f coordination polymers based on elliptical triple-deck cylinders hinged by meso-double helical chains

Two 2-D 4d–4f coordination polymers based on elliptical triple-deck cylinders hinged by meso-helical chains containing an isonicotinate ligand, namely, {[Ag2Ln(IN)4(H2O)2]·(NO3)·(H2O)}n (Ln = Sm and Eu, IN− = isonicotinate), have been successfully constructed through the transformation of a single-crystal to single-crystal (SC-SC) or different metal–organic polymer units, in which the recognition between the organic ligand and two types of metal ions direct the formation of the final productions.

Temperature- and solvent-controlled dimensionality in a zinc 6-(1H-benzoimidazol-2-yl)pyridinecarboxylate system

Several 0D, 1D, and 3D metal–organic hybrid frameworks of ZnII have been synthesized by using the asymmetric ligand 6-(1H-benzoimidazol-2-yl)pyridinecarboxylic acid (HL) with control of the temperature and solvent in a solvothermal synthesis technique. In DMF, the structure at room temperature confirms that the resulting compound Zn(L)2·2(H2O) (1) is the 0D mononuclear structure, above ∼80 °C, C–N bond cleavage of partial DMF molecules induces the formation of the 1D chain-like compound {[Zn(L)(HCOO)]·2(H2O)}n (2), but on warming up to 120 and 160 °C, due to the decomposition of a large number of DMF molecules, the same reaction, respectively, gives two 3D metal–organic coordination polymers with 3D channels reported previously {[Zn(HCOO)3]−·[H2N(CH3)2]+}n (3) and [Zn(HCOO)2]n (4), in which the 3D channels of 3 contain guest [H2N(CH3)2]+ motifs, while at high temperature the 3D channels of 4 are an open stable system without any guest molecules. Replacing DMF in the above reaction by ethanol or acetonitrile, only 0D compound 1 is obtained in the range from room temperature to 160 °C. However, the same reaction in DMSO provides a 1D wave-like compound {[Zn(L)(DMSO)]·(ClO4)·H2O}n (5), in which the solvent DMSO molecule coordinates to the central metal ZnII ion. Furthermore, in three new complexes 1, 2 and 5, through π⋯π stacking and hydrogen bonding interactions, 3D supramolecular networks are assembled. It is worth noting that the existence of the twelve-membered cyclic water–perchlorate dimers [(ClO4)⋯(H2O)]22− with chair-conformation in the solid state of 5 not only increases the stability of the supramolecular structure, but also results in a stronger fluorescence signal compared with ligand HL, 1 and 2.

Partially cyclopentadienyl-substituted tetranuclear lanthanide Schiff base complexes

Treatment of Cp 3 Ln (Ln=Pr, Nd) with an equimolar amount of the Schiff base bis(acetylacetone)ethylenediamine (H 2 acacen) half hydrate (H 2 L 1 ·1/2H 2 O) or bis(salicylidene)trimethylenediamine (H 2 saltn) half hydrate (H 2 L 2 ·1/2H 2 O) in THF affords three novel μ-hydroxo-bridged tetranuclear organolanthanide complexes [η 5 -CpLn 2 L 2 (μ-OH)] 2 · n THF, L=L 1 , n =4, Ln=Pr ( 1 ), Nd ( 2 ); L=L 2 , n =2, Ln=Nd ( 3 ). A reaction scheme was proposed in which the cyclopentadienyl lanthanide coordination motif [CpLnL] ( A ) and the hydroxyl lanthanide motif [LnL(OH)] ( B ) cross-reacted and then dimerized through the μ-hydroxo bridges to give the tetranuclear Ln complexes containing an Ln 4 O 8 skeleton with two reciprocally oriented face-sharing defect cubanes. In each monomeric species [CpLn 2 L 2 (OH)] ( C ) the Ln atoms are 8- or 9-coordinated. All complexes have been characterized by EA, IR and Mass spectroscopy.

Construction of a novel Zn-Ni trinuclear Schiff base and a Ni2+ chemosensor.

A novel Zn-Ni heterotrinuclear Schiff base compound bearing acacen(2-) moieties was constructed through the selective assembly of a chemosensor Schiff base zinc compound with a Ni(2+) ion. Its crystal structure not only clearly explains the binding mode between the chemosensor molecule and the detected metal ion but also represents the first trinuclear complex based on a symmetric acacen(2-) base Schiff base.

Syntheses and characterization of copper(II) complexes of bis(acetylacetone)trimethylenediimine

Abstract Copper(II) complexes [Cu(acactn)H2O]2 (1) and [Cu2(acactn)2KClO4]2 (2), where H2acactn is a tetradentate Schiff base bis(acetylacetone)trimethylenediimine, have been prepared and characterized by IR, CV and X-ray single crystal structure analyses. The ligand H2acactn is strongly metallophilic to stabilize Cu(II) ion with a square planar N2O2 coordination environment. Complex 1 can be seen as a hydrogen-bonded dimer of building block Cu(acactn) via bridging water molecules, while complex 2 is a tetrametric adduct of [Cu(acactn)] moiety and KClO4, in which K+ and ClO4− are the bridging-groups. Electrochemical studies displayed that Cu(II)/Cu(I) is an irreversible one-electron reduction process.

Lithium-Ion-Battery Anode Materials with Improved Capacity from a Metal–Organic Framework

We present a porous metal-organic framework (MOF) with remarkable thermal stability that exhibits a discharge capacity of 300 mAh g(-1) as an anode material for a lithium-ion battery. Pyrolysis of the obtained MOF gives an anode material with improved capacity (741 mAh g(-1)) and superior cyclic stability.

Three-fold parallel interlocking of 2-D brick-wall networks showing ladder-like unsymmetrical Borromean links

Reaction of a semi-rigid ditopic ligand, N,N′-bis(4-pyridylmethyl)pyromellitic diimide (L), with HgI2 afforded the 2-D brick-wall type (6,3) networks, which interlocked in a parallel fashion to give the first example of unsymmetrical Borromean ladder links.

Temperature-/solvent-dependent low-dimensional compounds based on quinoline-2,3-dicarboxylic acid: structures and fluorescent properties.

A series of 0-D, 1-D, and 2-D metal-organic compounds through reactions of quinoline-2,3-dicarboxylic acid (2,3-H(2)qldc) with transition metal salts MCl(2), namely, M(2,3-Hqldc)(2)(H(2)O)(2) (M = Co(1), Zn(4) and Cd(7)), [M(3-qlc)(2)(H(2)O)(2)](n) (M = Co(2), Zn(5) and Cd(8)), M(2-qldc-3-OCH(3))(2)(CH(3)OH)(2) (M = Co(3) and Zn(6)) and [Cd(2,3-qldc-OCH(3))(μ(2)-Cl)](2n) (9) (where, 3-Hqlc = quinoline-3-carboxylic acid and 2-qldc-3-OCH(3) = 3-(methoxycarbonyl)quinoline-2-carboxylic acid), were synthesized and characterized by elemental analysis, IR, thermogravimetric analysis (TG), and single-crystal X-ray diffraction. When the temperature ranged from room temperature to 70 °C, three isomorphous mononuclear complexes 1, 4 and 7 were obtained in H(2)O/H(2)O + CH(3)OH. As the temperature rose further to above 90 °C, due to the decomposition of 2-position carboxyl group in ligand 2,3-H(2)qldc, the same reactions, respectively, produced three isomorphous 2-D layer-like structures 2, 5 and 8 with 4(4) topology in water. By contrast, when the mixed solvent of H(2)O + CH(3)OH at a 1 : 1 ratio (v/v) was applied, the three above-mentioned reactions respectively gave compounds 3, 6 and 9 with the 3-position esterification of 2,3-H(2)qldc. Compounds 3 and 6 are mononuclear and isomorphous, while complex 9 has a 1-D double-stranded chain-like structure connected by two μ(2)-Cl bridges. Obviously, these results reveal that the reaction temperature and solvent play a critical role in structural direction of these low-dimensional compounds. Meanwhile, the photoluminescent property of the selected compounds is also investigated.

Construction of three high-dimensional supramolecular networks from temperature-driven conformational isomers

Under different temperatures, the reaction mixture of the multidentate organic ligand usy-L4 and Zn(NO3)2 + NaN3 crystallized to give three conformational isomers, namely Zn(usy-L4)(η1-N3)2 (α-1, β-2 and γ-3) (usy-L4 = N,N-dimethyl-2-(pyridin-2-ylmethylimino)ethanamine). Single-crystal X-ray diffraction analyses reveal that the conformational isomerism of three compounds 1–3 stems from the different orientations of two azide groups with η1-terminal nitrogen atom coordinating to central zinc ion in reference to the basal chelating plane of ligand usy-L4, and further resulting in different supramolecular networks with two-dimensional 44 rhombic-grid for α-1, a three-dimensional 36·418·53·6 compressed-NbO framework for β-2, and a three-dimensional “dense” 424·64 topology for γ-3. Meanwhile, three isomers may be also irreversibly converted from 1 to 2, to 3 through SC-to-SC transformation driven by temperature.