Ladder-like Framework Research Articles

Synthesis, Structural Characterization and Ligand-Enhanced Photo-Induced Color-Changing Behavior of Two Hydrogen-Bonded Ho(III)-Squarate Supramolecular Compounds.

Two coordination polymers (CPs) with chemical formulas, [Ho2(C4O4)2(C2O4)(H2O)8]·4H2O (1) and [Ho(C4O4)1.5(H2O)3] (2), (C4O42− = dianion of squaric acid, C2O42− = oxalate), have been synthesized and their structures were determined by single-crystal X-ray diffractometer (XRD). In compound 1, the coordination environment of Ho(III) ion is eight-coordinate bonded to eight oxygen atoms from two squarate, one oxalate ligands and four water molecules. The squarates and oxalates both act as bridging ligands with μ1,2-bis-monodentate and bis-chelating coordination modes, respectively, connecting the Ho(III) ions to form a one-dimensional (1D) ladder-like framework. Adjacent ladders are interlinked via O–H⋅⋅⋅O hydrogen bonding interaction to form a hydrogen-bonded two-dimensional (2D) layered framework and then arranged orderly in an AAA manner to construct its three-dimensional (3D) supramolecular architecture. In compound 2, the coordination geometry of Ho(III) is square-antiprismatic eight coordinate bonded to eight oxygen atoms from five squarate ligands and three water molecules. The squarates act as bridging ligands with two coordination modes, μ1,2,3-trismonodentate and μ1,2-bis-monodentate, connecting the Ho(III) ions to form a 2D bi-layered framework. Adjacent 2D frameworks are then parallel stacked in an AAA manner to construct its 3D supramolecular architecture. Hydrogen bonding interactions between the squarate ligands and coordinated water molecules in 1 and 2 both play important roles on the construction of their 3D supramolecular assembly. Compounds 1 and 2 both show remarkable ligand-enhanced photo-induced color-changing behavior, with their pink crystals immediately turning to yellow crystals under UV light illumination.

Artificial neural network cascade identifies multi-P450 inhibitors in natural compounds.

Substantial evidence has shown that most exogenous substances are metabolized by multiple cytochrome P450 (P450) enzymes instead of by merely one P450 isoform. Thus, multi-P450 inhibition leads to greater drug-drug interaction risk than specific P450 inhibition. Herein, we innovatively established an artificial neural network cascade (NNC) model composed of 23 cascaded networks in a ladder-like framework to identify potential multi-P450 inhibitors among natural compounds by integrating 12 molecular descriptors into a P450 inhibition score (PIS). Experimental data reporting in vitro inhibition of five P450 isoforms (CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4) were obtained for 8,148 compounds from the Cytochrome P450 Inhibitors Database (CPID). The results indicate significant positive correlation between the PIS values and the number of inhibited P450 isoforms (Spearman’s ρ = 0.684, p < 0.0001). Thus, a higher PIS indicates a greater possibility for a chemical to inhibit the enzyme activity of at least three P450 isoforms. Ten-fold cross-validation of the NNC model suggested an accuracy of 78.7% for identifying whether a compound is a multi-P450 inhibitor or not. Using our NNC model, 22.2% of the approximately 160,000 natural compounds in TCM Database@Taiwan were identified as potential multi-P450 inhibitors. Furthermore, chemical similarity calculations suggested that the prevailing parent structures of natural multi-P450 inhibitors were alkaloids. Our findings show that dissection of chemical structure contributes to confident identification of natural multi-P450 inhibitors and provides a feasible method for virtually evaluating multi-P450 inhibition risk for a known structure.

Crystal structures, fluorescent and magnetic properties of five new coordination polymers based on biphenyl-3,4′,5-tricarboxylic acid

Five new coordination polymers, {[Cd3(bpt)2(DMF)2]·(H2O)2}n (1), [Cd(Hbpt)(bipy)0.5(H2O)]n (2), [Cd2(bpt)(phen)2Cl]n (3), {[Cu2(bpt)(phen)(μ2–OH)(H2O)]·(H2O)2}n (4) and {[Mn5(Hbpt)4(phen)4(μ2–OH)2(H2O)2]·(H2O)2(CH3CN)2}n (5) have been prepared through hydro(solvo)thermal reactions of H3bpt (H3bpt=biphenyl-3,4′,5-tricarboxylic acid) with different pyridyl-containing auxiliary ligands (bipy=4,4′-bipyridine and phen=1,10-phenanthroline). Compound 1 represents a 3D ladder-like framework composed of rod-shaped infinite chains. In 2, the bridging ligand bipy links binuclear cadmium ions to generate a 2D layer. Compound 3 features a 1D ladder structure and further linked by π–π stacking interaction to form a 3D supramolecular network. Compound 4 exhibits a binodal 3-connected net which features the Schlafli symbol of (4·82). Compound 5 contains trimetallic cluster and binuclear unite which are further linked by Hbpt ligand to form a 2D layer. Moreover, photoluminescent properties of compounds 1–3 were studied in the solid state. Magnetic susceptibility measurements indicate that compound 4 exhibits ferromagnetic exchange interactions, whereas compound 5 displays antiferromagnetic exchange interactions.

Reversible Solid-State Structural Transformation of a 1D−2D Coordination Polymer by Thermal De/Rehydration Processes

A new coordination polymer, [Zn(HBTC)(BPE)0.5(H2O)]n·nH2O (1) with an extended 1D ladderlike metal-organic framework (MOF) has been synthesized and structural characterized by single-crystal X-ray diffraction method. Structural determination reveals that, in compound 1, the Zn(II) ion is four-coordinated in a distorted tetrahedral geometry, bonded to one nitrogen atom from one BPE ligand, and three oxygen atoms from two monodentate carboxylate groups of two HBTC(2-) ligands and one coordinated water molecule. The HBTC(2-) acts as a bridging ligand with a bis-monodentate coordination mode, connecting the Zn(II) ions to form a one-dimensional (1D) [Zn(HBTC)] chain. Two 1D chains are then interlinked via the connectivity between the Zn(II) ions and anti-BPE liagnds to complete the 1D ladderlike MOF. Adjacent 1D Ladders are further extended to a 2D hydrogen-bonded layered network through the intermolecular O-H · · · O hydrogen bond between the carboxylic group and carboxylate group of interladder HBTC(2-) ligand. Adjacent 2D layers are then packed orderly in an ABAB-type array via the intermolecular interactions of combined π-π interaction and O-H · · · O hydrogen bonds to form a 3D supramolecular architecture exhibiting 1D channels intercalated with guest water molecules. The reversible solid-state structural transformation between crystalline 1 with 1D ladderlike framework and its dehydrated powder 2, [Zn(HBTC)(BPE)0.5]n, with 2D framework via the displacement of coordinated water molecule to HBTC(2-) ligand, by thermal de/rehydrated processes has been verified by PXRD measurements. The emission of 1 and 2 is ascribed to a ligand-based transition.

Syntheses, structures and magnetic properties of two new one-dimensional cobalt (II) phosphites with organic amines acting as ligands

Two new one-dimensional (1D) inorganic–organic hybrid cobalt (II) phosphites Co(HPO 3) (py) ( 1) and [Co(OH)(py) 3][Co(py) 2][HPO 2(OH)] 3 ( 2) have been prepared under solvothermal conditions in the presence of pyridine (py). Compound 1 crystallizes in the monoclinic system, space group p2(1)/ c, a=5.3577(7) Å, b=7.7503(10) Å, c=17.816(2) Å, β=94.327(2)°, V=737.67(16) Å 3, Z=4. Compound 2 is orthorhombic, Cmcm, a=16.3252(18) Å, b=15.7005(16) Å, c=13.0440(13) Å, β=90.00° V=3343.4(6) Å 3 and Z=4. Compound 1 possesses a 1D ladder-like framework constructed from CoO 3N tetrahedral, HPO 3 pseudo-pyramids and pyridine ligands. While compound 2 is an unusual inorganic–organic hybrid 1D chain, which consists of corner-shared six-membered rings made of CoO 3N 3/CoO 4N 2 octahedra and HPO 3 pseudo-pyramids through sharing vertices.

Hydrothermal synthesis, crystal structure and characterization of a new 1-D supramolecular ladder based on a binuclear CdII complex [Cd2L4(3,5-DNBA)2](H2O) with L as a bridging ligand (L=3-(2-pyridyl)pyrazole; 3,5-DNBA=3,5-dinitrobenzoate)

A new 1-D cadmium(II) mixed ligand dimer supramolecular ladder [Cd2 L 4(3,5-DNBA)2]H2O (1), (L = 3-(2-pyridyl)pyrazole and 3,5-DNBA = 3,5-dinitrobenzoate) was synthesized by hydrothermal methods. X-ray structural analysis of complex 1 revealed that two cadmium(II) cores are bridged by two deprotonated pyrazole groups of L, leading to dinuclear cadmium(II) [Cd2 L 4(3,5-DNBA)2]. The dimers are joined by hydrogen-bonding interactions between two different cadmium(II) dimers to form a one-dimensional ladder-like framework and stabilized by weak π–π interactions. Moreover, the fluorescence spectrum of compound 1 exhibits blue fluorescent emission in the solid state at room temperature.

Synthesis and Characterization of Ladder-like Poly(vinylsilsesquioxanes)

Ladder-like poly(vinylsilsesquioxanes)(LPVS) containing four parallel chains in the skeleton were synthesized by two steps: first, LPVS were prepared by a template sol–gel method from vinyltrichlorosilane (VTCS); then adjacent pendent vinyl groups were polymerized side by side along the LPVS chain. The resulting polymers (LPVS-2) were characterized by Fourier transform infrared, 1H NMR, 29Si NMR, thermogravimetric analysis (TGA), transmission electron microscopy, scanning electron microscopy, X-ray diffraction and elemental analysis. Experimental results reveal that both LPVS and LPVS-2 have a highly regular, ladder-like framework, and that most of the vinyl groups have taken part in the side-by-side polymerization reaction. There is no evidence that crosslinking between macromolecular chains has occurred during this process. TGA data indicate that LPVS-2 (with pendent vinyl polymerized) possesses better thermal stability than that of LPVS. For the former, no weight loss can be detected until 500°C, which is attributed to its highly regular ladder-like framework consisting of a four-parallel-chain structure.

A novel optical limiting coordination polymer with ladder-like framework

The optical limiting (OL) properties of a novel coordination polymer {[Et4N][Ag2I3]}n with a ladder-like framework were investigated using 532-nm nanosecond laser pulses. The coordination polymer in dimethylformamide solution exhibits better OL performance than C60 in toluene. The results were discussed using a phenomenological model based on excited-state nonlinear absorption.

Novel one-dimensional polymers generated from p-Ferrocenylbenzoate: syntheses, structures, and magnetic properties.

Treatment of p-ferrocenylbenzoate [p-HOOCH4C6Fc, Fc = (eta5-C5H5)Fe(eta5-C5H5)] with Mn(OAc)2 x 2H2O or Cd(OAc)2 x 2H2O afforded one-dimensional linear chain polymer [[Mn(OOCH4C6Fc)2(mu2-OH2)(H2O)2](H2O)]n (1), double-bridge polymer [Mn(mu2-OOCH4C6Fc)2(phen)]n (phen = phenanthroline) (2), and ladderlike framework [[Cd(mu2-OOCH4C6Fc)(eta2-OOCH4C6Fc)(bbp)](CH3OH)]n (bbp = 4,4'-trimethylene-dipyridine) (3). The solution-state cyclic voltammograms indicate that the half-wave potentials of the ferrocenyl moieties in these polymers are all shifted to positive potential compared to that of sodium p-ferrocenylbenzoate. Both 1 and 2 behave as 1D Heisenberg Mn(II) chains with weak intrachain antiferromagnetic interactions between the local high-spin Mn(II) ions, and the exchange coupling parameters J (-5.20 and -3.25 cm(-1) for 1 and 2, respectively) are larger than those of most of the reported di-Mn(II) complexes that contain mu2-aqua and mu2-carboxylato units and one-dimensional Mn(II) carboxylic polymers.

ISOLATION AND X-RAY CRYSTAL STRUCTURES OF {Li2[μ2-As(SiMe3)2][μ3-As(SiMe3)2](THF)}2 AND [(Me3Si)2AsLi(THF)2]2

Abstract The lithium arsenides {Li2[μ2-As(SiMe3)2] [μ3-As(SiMe3)2](THF)}2 (I) (THF = tetrahydrofuran) and [(Me3Si)2AsLi(THF)2]2 (II) were isolated and their solid-state structures determined by X-ray methods. Compound I crystallizes in the monoclinic system, space group P21/c, with a = 10.147(1)A, b = 19.665(2)A, c = 16.768(2)A, β = 107.78(1)° and Z = 2. The core structure consists of an [LiAs]4 ladder-like framework with four antiparallel adjacent As-Li rungs. The two lithium atoms of the central ring each bridge three arsenic centers while the two lithium atoms belonging solely to the outer rings each span two arsenic atoms and are coordinated to one THF molecule. Monoclinic crystals of compound II belong to space group C2/c, with a = 17.877(4) A, b = 14.077(3) A, c = 19.006(4) A, β = 109.16(2)° and Z = 4. The structure consists of a centrosymmetric dimer containing a four-membered As-Li-As-Li ring wherein each lithium atom is coordinated to two molecules of THF.