Chenxia Du

A linear piperazine-pyridine ligand and its Hg coordination polymer

Abstract Reaction of piperazine hexahydrate with 4-chloromethylpyridine hydrochloride affords a new piperazine–pyridine ligand: N,N′-bis(4-pyridylmethyl)piperazine (bpmp). X-ray structure analysis confirms an overall linear structure, in which the lone electron pairs of piperazine-N are in trans-position. Its zigzag polymer with Hg2+ was readily obtained in THF. Bpmp is held in the chair conformation in the polymer, and Hg2+ coordinates to two N atoms from different bpmp ligands and two I atoms.

Structural and magnetic properties of O-bridged tetranuclear and binuclear Cu(II) complexes

Abstract Two copper(II) complexes [Cu 4 (L 1 ) 4 ] ( 1 ) and [Cu 2 (phen) 2 (HL 2 ) 2 ] (ClO 4 ) 2 ( 2 ) have been synthesized from two potentially tridentate ligands N -(2-hydroxybenzyl) propanolamine (H 2 L 1 ) and N -(2-hydroxybenzyl) ethanolamine (H 2 L 2 ). X-ray analyses revealed that 1 contains a Cu 4 O 4 cubane core, with each two Cu(II) atoms bridged by a pair of alkoxides; 2 has a bis(μ 2 -phenoxo)-bridged dicopper(II) structure. Variable temperature magnetic measurements of 1 have revealed that the correlation between 2 J and the bridge angles φ for 1 shows a very strong antiferromagnetic tendency, i.e. the ferromagnetic and antiferromagnetic interactions cross at the φ of 94.5°. The relatively weak antiferromagnetic interactions (2 J =−226.8 cm −1 ) with respect to the bridge angles ( φ =100.4°) for 2 have been ascribed to the pyramidal distortions at the phenoxide oxygen atoms in addition to the unfavorable overlaps of the magnetic orbitals for the highly distorted copper coordination polyhedra.

Self-assembly of a new “4,4′-bipyridyl-based” building block with Cd(II) and Co(II) cations: synthesis and crystal structures of 1- and 2-D coordination polymers

Abstract We synthesized a new “4,4′-bipyridyl-based” building block, 1,4-(di-4-pyridyl) methoxy benzene (bpmob), which appears as two kinds of isomers: trans- and cis-modes. The building block self-assembled into one-dimensional coordination polymer [Cd(NO3)2(cis-bpmob)2]n·[Cd(NO3)2(trans-bpmob)(H2O)]2n (I) with Cd(II), and two-dimensional coordination polymer [Co(NCS)2(trans-bpmob)2]n (II) with Co(II). Polymer I consists of two parts: double zig-zag linear chain and ladder-like one-dimensional chain, trans- and cis-modes exist simultaneously in the polymer. Polymer II shows a two-dimensional plane network structure with rhombohedral grids, and the polymer also exhibits layered packing in its solid-state structure.

Oxidative cyclization and coordinate polymerization of N-benzoyl-N′-(2-pyridyl)thiourea with copper(II) chloride

Abstract A chloride-bridged one-dimensional Cu(II) coordination polymer is prepared by the treatment of N-benzoyl-N′-(2-pyridyl)thiourea with a large excess of Cu(II)Cl2 in ethanol solution via oxidative cyclization and coordinate polymerization.

Synthesis, crystal structure and properties of the zinc complexes with unsymmetrical tridentate ligands

Abstract Two complexes of zinc (II) with mixed-ligand, [Zn2(phen)2(HL1)2] (ClO4)2 (1) and [Zn2(phen)2(HL2)2] (ClO4)2(2) (H2L1N–(2-hydroxybenzyl) ethanolamine and H2L2=N–(2-hydroxybenzyl) propanolamine), and another zinc complex ZnL1 (3) were synthesized and characterized by elemental analysis, IR spectra, thermal analysis, fluorescence and 1H NMR. The crystal structure of (1) has a centrosymmetric di-phenoxo-bridged dizinc (II) core and each zinc center is laid in a slightly distorted trigonal bipyramidal geometry. A 2D supramolecular structure is formed approximately along bc plane in terms of the action of multiple N–H⋯O and O–H⋯O hydrogen bonds between the (HL1)− ligands and the π⋯π stacking interactions between the phenanthroline ligands. Thermal behavior, studied by TG and DTA in nitrogen atmosphere, indicates that phen is eliminated at higher temperature than (HL1)− and (HL2)−. Several possible mechanisms for the fluorescence quenching of the metal complexes are proposed.

Structure and Spectroscopic Studies of 4,8-bis(2-Hydroxybenzyl)-cis-octahydro[1,4]-oxazino [3,2-b]-1,4-oxazine

The title compound 4,8-bis(2-Hydroxybenzyl)-cis-octahydro [1,4]-oxazino [3,2-b]-1,4-oxazine (1) has been synthesized by the reaction of N-(2-hydroxybenzyl)-2-amino-1-ethanol with glyoxal. This novel compound was characterized by elemental analysis, IR, and 1H NMR. The structure was also confirmed by a single crystal X-ray study. The compound crystallizes in monoclinic C2/C space group with unit cell dimensions: a = 18.318(4), b = 8.6110(17), c = 13.267(3) Å, β = 119.90(3)○, V = 1814.1(6) Å3, Z = 4. The two fused six-membered rings in 1 adopt chairlike conformations slightly flattened around the nitrogen atoms. In the central fusion bond, the geometry is a staggered conformation, with the two angular hydrogen atoms in the cis positions with respect to the rings, the nitrogen atoms antiperiplanar to each other, while the oxygen atoms remain gauche to each other and antiperiplanar to the hydrogen atoms. The ring conformations in 1 have been discussed on the basis of the anomeric effects and the presence of two strong intramolecular hydrogen bonds between the phenolic hydrogens and the amino groups.

Synthesis, crystal structure and spectroscopic characterization of a hydrogen-bonded 1D copper(II) complex

AbstractNovel 1:2 and 1:1 (M:L) copper(II) complexes have been prepared from the tridentate ligand 2-(1-methyl-2-aza-5-oxapentyl)phenol (H2L1). The crystal structure of [Cu(HL1)2] (1) exhibits a noncentrosymmetric square-planar geometry with a slightly tetrahedral distortion. The CuII atom is coordinated by two amino N and two phenoxo O atoms of two (HL1)− ligands. The phenoxo and the alkoxy groups are involved in two strong intramolecular hydrogen bonds. The coordination moieties are further connected to a 1D linear structure by the action of intermolecular hydrogen bonds between the alkoxyl and the amino groups. The importance of steric hindrance introduced by the methyl group in the molecular structure and the packing of the complex molecules has been demonstrated. The e.p.r. parameters of (1) have been obtained: g∥ = 2.231, g⊥ = 2.005, giso = 2.080, A∥ = 185.0 G, Aiso = 86.5 G, A⊥ = (3Aiso − A∥)/2 = 37.3 G. These results confirm a distorted square planar stereochemistry with a (

A novel 3D cadmium coordination complex [Cd(H 2 L)·1.5H 2 O] n with strong photoluminescent property: (H 4 L= N , N ′-bis(4-pyridylcarboxyl)-2,6-pyridine dicarbohydrazide)

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