Youfu Zhou

Lanthanide–transition metal coordination polymers based on multiple N- and O-donor ligands

Lanthanide-transition metal (Ln-M) coordination polymers have attracted extensive interest because they exhibit novel physical properties originating from the interactions between distinct metal ions. This review mainly describes our recent work in the design of Ln-M coordination polymers through the assembly of different metal ions and organic ligands, especially the ligands with multiple N- and O-donor atoms. Many of these crystalline Ln-M materials exhibit intriguing structural motifs and interesting magnetic properties.

Syntheses, crystal structures and photoluminescent properties of two isophthalate-bridged complexes

Abstract Two interesting isophthalate-bridged coordination polymers, [Cd2(2,2′-bpy)2(ip)2]n (1) and [Zn2(2,2′-bpy)2(ip)2]n (2) (2,2′-bpy=2,2′-bipyridine, ip=isophthalate) have been hydrothermally synthesized and structurally characterized. X-ray single-crystal diffraction analyses reveal that compound 1 contains a three-dimensional polymeric channel with tetra Cdip as building units and compound 2 forms a double-helical structure linked by Zn2O4C2 cores. In 1, one Cd(II) center is six-coordinated and the other is seven-coordinated, while the two Zn(II) centers in 2 are in different six-coordinated environments.

Design of metal-organic NLO materials: complexes derived from pyridine-3,4-dicarboxylate

Two new polymeric complexes, [Zn(pydc)]n (1) and [Co(pydc)(H2O)2]n·nH2O (2) (pydc = pyridine-3,4-dicarboxylate), have been synthesized and characterized. Complex 1 crystallizes in an acentric space group Pna21 and consists of a 3D network with unsymmetrical pydc linkers arranged in a parallel mode. Complex 2 crystallizes in the centric space group P−1, in which pydc ligands link Co(II) metal ions to generate a 2D layer structure with (4,4) topology nets. The Kurtz powder measurement shows that 1 exhibits a powder SHG efficiency about 5 times higher than that of potassium dihydrogen phosphate (KDP) and represents the first NLO-active 3D coordination network with parallel arrangement of dipolar ligands.

Solvent and temperature influence structural variation from nonporous 2D -> 3D parallel polycatenation to 3D microporous metal-organic framework

Three novel complexes constructed from the same initial materials, exhibiting the variation of architectures from nonporous 2D → 3D parallel polycatenation based on highly undulating (4,4) nets to 3D microporous pillar-layered network through influencing the interpenetration, have been successfully synthesized under different reaction conditions.

Luminescent sensing profiles based on anion-responsive lanthanide(III) quinolinecarboxylate materials: solid-state structures, photophysical properties, and anionic species recognition

Lanthanide complexes based on the quinolinecarboxylate ligand 2-phenyl-4-quinolinecarboxylic acid (PQC), namely, Ln2PQC6 (Ln = La3+, Pr3+, Nd3+, Sm3+ and Eu3+) were synthesized by a convenient solvothermal reaction, and the related crystal structures were determined. These complexes are isostructural and feature a discrete dinuclear moiety, in which solvent molecules act as coligands and the Ln3+ centre exhibits distorted tricapped trigonal prism geometry. By the introduction of the PQC ligand, the europium sample Eu2PQC6 (5) showing intense red emission in the solid state and solution, with both the replaceable coordination environment and potential hydrogen-bonding-accepting site, can be explored as a luminescent probe for sensing various anions. Among the tested ions (F−, Cl−, Br−, I−, NO3−, ClO4−, SCN−, HCO3−, HSO4− and H2PO4−), HSO4− and H2PO4− possess a strong response in the Eu3+ emitting behaviour leading to a unique quenching with a low detection limit of 15.3 and 8.3 nM, respectively, and a quick response time of less than 30 s. The different recognition mechanisms for two anions, including O–H⋯N hydrogen bonding and metal coordination modes have been proposed, which are supported by UV-vis, fluorescence spectroscopy, nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) measurements. In addition, density functional theory (DFT) calculations were carried out to verify the two recognition mechanisms of Eu2PQC6 in depth. As an extended research, Eu2PQC6 interaction with the nucleoside phosphates adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) in mixed aqueous solution was investigated, which can act as a special luminescent sensor for all three phosphates. The strong quenching by ADP (99.5%), has been ascribed to the strong bonding affinity (log Ka = 5.99) based on electrostatic attractions and steric effects.

Mechanical properties of Ti3SiC2 particulate reinforced copper prepared by hot pressing of copper coated Ti3SiC2 and copper powder

Abstract The compound Ti3SiC2 is a promising reinforcement for copper, but at a high volume content of Ti3SiC2, densification of Cu/Ti3SiC2 composites becomes difficult. To improve the densification behaviour and microstructure of Cu/Ti3SiC2 composites, Ti3SiC2 particulates were coated with a layer of copper by an electroless plating method before being incorporated into the copper matrix. Results demonstrated that, compared with uncoated Ti3SiC2 reinforced copper, copper coated Ti3SiC2 reinforced composites exhibit both high density and a homogeneous distribution of Ti3SiC2 within the copper matrix. The precoated layer of copper prevents direct contact and agglomeration of Ti3SiC2 particulates. Owing to the improved density and microstructure, the mechanical properties of Cu/Ti3SiC2 composites are also enhanced. Mechanical property investigation revealed that a significant strengthening effect is observed for Cu/Ti3SiC2 composites at both room and high temperatures.

Effect of Yb3+ concentration on upconversion luminescence of AlON:Er3+ phosphors

Abstract AlON:1.6 mol.%Er 3+ , x mol.%Yb 3+ ( x =0, 2.6, 3.1, 3.6, 4.1, 4.6) phosphors were synthesized successfully by aluminothermic reduction and nitridation (ATRN) method and characterized by X-ray diffraction (XRD), scanning electron microscopy (FESEM) and upconversion photoluminescence (UCPL) emission spectra. Under the excitation of diode laser 980 nm, the green (556 nm) and red (655 nm) upconverted emissions were observed, attributed to the 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transition of Er 3+ respectively. The emission intensity increased with increasing Yb 3+ concentration due to the energy transfer (ET) between Yb 3+ and Er 3+ . The upconverted emission reached the highest as x =3.6, and was pump-power dependent involving a two-photon process.

CCDC 830313: Experimental Crystal Structure Determination

Related Article: Youfu Zhou, Wentao Xu, Mingyan Wu, Anjian Lan, Linjie Zhang, Rui Feng, Feilong Jiang, Maochun Hong|2012|Inorg.Chem.Commun.|15|140|doi:10.1016/j.inoche.2011.10.010

Formation and orientation control of Y2O3 inclusions in pulsed laser deposited YBa2Cu3O7−δ films by using a melt-textured target

The formation and orientation Of Y2O3 inclusions in pulsed laser deposited YBa2Cu3O7-delta films by using Y2BaCuO5-containing melt-textured target have been studied by X-ray diffractometry and transmission electron microscopy. The results show that Y2O3 inclusions, rather than the Y2BaCuO5 phase contained in the target, are formed in the films. [1 1 1]- and [10 0]-oriented Y2O3 inclusions have been found in the YBa2Cu3O7-delta films. The orientation Of Y2O3 inclusions is dependent on the deposition temperature. If the deposition temperature is high enough, [I I 1]-oriented Y2O3 can be inhibited. The reasons for the formation Of Y2O3 inclusions and their orientation are discussed