Xiao-Zeng You

Fine-Tuning Pore Size by Shifting Coordination Sites of Ligands and Surface Polarization of Metal–Organic Frameworks To Sharply Enhance the Selectivity for CO2

Based upon the (3,6)-connected metal-organic framework {Cu(L1)·2H(2)O·1.5DMF}(∞) (L1 = 5-(pyridin-4-yl)isophthalic acid) (SYSU, for Sun Yat-Sen University), iso-reticular {Cu(L2)·DMF}(∞) (L2 = 5-(pyridin-3-yl)isophthalic acid) (NJU-Bai7; NJU-Bai for Nanjing University Bai group) and {Cu(L3)·DMF·H(2)O}(∞) (L3 = 5-(pyrimidin-5-yl)isophthalic acid) (NJU-Bai8) were designed by shifting the coordination sites of ligands to fine-tune pore size and polarizing the inner surface with uncoordinated nitrogen atoms, respectively, with almost no changes in surface area or porosity. Compared with those of the prototype SYSU, both the adsorption enthalpy and selectivity of CO(2) for NJU-Bai7 and NJU-Bai8 have been greatly enhanced, which makes NJU-Bai7 and NJU-Bai8 good candidates for postcombustion CO(2) capture. Notably, the CO(2) adsorption enthalpy of NJU-Bai7 is the highest reported so far among the MOFs without any polarizing functional groups or open metal sites. Meanwhile, NJU-Bai8 exhibits high uptake of CO(2) and good CO(2)/CH(4) selectivity at high pressure, which are quite valuable characteristics in the purification of natural gases.

Highly Efficient Green and Blue-Green Phosphorescent OLEDs Based on Iridium Complexes with the Tetraphenylimidodiphosphinate Ligand

Two novel bis-cyclometalated iridium complexes are successfully applied in organic light-emitting diodes (OLEDs). Because of their better carrier transport ability and shorter excited stated lifetimes, good electroluminescence performances of the complexes are observed.

Slow relaxation processes and single-ion magnetic behaviors in dysprosium-containing complexes.

A series of one-dimensional complexes [Ln(L(1))(3)(HOCH(2)CH(2)OH)](n) (L(1) = 2-furoate anion; Ln = Nd (1), Sm (2), Gd (3), Tb (4), Dy (5), Er (6)) have been synthesized. The complexes were crystallized in the monoclinic space group P2(1)/c and show a chain-like structure determined by single-crystal X-ray diffraction. Magnetic properties indicate that carboxyl group of 2-furoate mediates different magnetic couplings in light and heavy rare earth complexes, namely, antiferromagnetic interaction between light rare earth ions and ferromagnetic interaction between heavy ones. Noticeably, complex 5 displays a strong frequency dependence of alternating current (AC) magnetic properties. Further magnetic studies show a distribution of a single relaxation process in 5. While 1,10-phenanthroline and phthalate anion (L(2)) were employed, [Dy(2)(L(2))(6)(H(2)O)](n) (7) was isolated by hydrothermal reactions and characterized magnetically. Research results also show the frequency dependence of AC magnetic susceptibilities, although the phthalate anions mediate antiferromagnetic coupling between Dy(III) ions. Further magnetic investigation of a neutral mononuclear complex with the formula [Dy(TTA)(3)(L(3))] (8) (TTA = 2-thenoyltrifluoroacetonate; L(3) = 4,5-pinene bipyridine) suggests that the single-ion magnetic behavior originates the slow relaxation of Dy(III)-containing complexes.

A highly stretchable autonomous self-healing elastomer

It is a challenge to synthesize materials that possess the properties of biological muscles-strong, elastic and capable of self-healing. Herein we report a network of poly(dimethylsiloxane) polymer chains crosslinked by coordination complexes that combines high stretchability, high dielectric strength, autonomous self-healing and mechanical actuation. The healing process can take place at a temperature as low as -20 °C and is not significantly affected by surface ageing and moisture. The crosslinking complexes used consist of 2,6-pyridinedicarboxamide ligands that coordinate to Fe(III) centres through three different interactions: a strong pyridyl-iron one, and two weaker carboxamido-iron ones through both the nitrogen and oxygen atoms of the carboxamide groups. As a result, the iron-ligand bonds can readily break and re-form while the iron centres still remain attached to the ligands through the stronger interaction with the pyridyl ring, which enables reversible unfolding and refolding of the chains. We hypothesize that this behaviour supports the high stretchability and self-healing capability of the material.

Unprecedented interweaving of single-helical and unequal double-helical chains into chiral metal–organic open frameworks with multiwalled tubular structures

Two novel chiral metal-organic open frameworks with unprecedented multiwalled tubular channels and interweaving of single-helical and unequal double-helical units were reported, which possess novel four-connected 4(2)8(3)10 topology and represent the first examples of functional metal-organic frameworks based on both flexible tripodal and flexible bisdentate ligands.

Crystal structure and spectroscopic studies on metal complexes containing ns donor ligands derived from S-benzyldithiocarbazate andp-dimethylaminobenzaldehyde

Abstract A series of neutral bis-ligand Cu II , Ni II , Pd II and Pt II chelates with Schiff base ligands derived from S-benzyldithiocarbazate and p -dimethylaminobenzaldehyde were prepared and characterized. The Schiff base acts as a single, negatively charged bidentate ligand forming stable neutral metal complexes. Magnetic and spectroscopic data suggest a square-planar structure for the Ni II , Pd II and Pt II chelates. Also, ESR spectral and variable-temperature magnetic suspectibility data support the square-planar structure of Cu II chelate. Cyclic voltammograms show that the coordination ability of the metal is the main factor influencing the redox potential of the Schiff base ligand in the complexes. Single cyrstal X-ray diffraction analysis of the nickel(II) chelate established that the Schiff base has lost a proton from its tautometric thiol form and coordinated to Ni II via the mercapto sulphur and β-nitrogen. The geometry around Ni II is square-planar with two equivalent Ni N and Ni S bonds; the two dimethylaminophenyl rings and the coordinated plane are almost in one plane forming an electronic delocalization system.

Distinct magnetic dynamic behavior for two polymorphs of the same Dy(III) complex

Two polymorphs of the same Dy(III) complex show distinct slow magnetic relaxation behaviors due to the different local environments of Dy(III) in the crystal. This work represents the first example where the magnetic dynamic property of neutral rare earth complexes could be tuned by growing polymorphic crystals without changing the ligand.

A highly selective and sensitive fluorescent turn-on sensor for Hg2+ and its application in live cell imaging

A boron-dipyrromethene (BODIPY) derivative containing a tridentate diaza-oxa ligand (8H-BDP) was synthesized as a fluorescent turn-on chemosensor for Hg(2+) with high sensitivity (detection limit < or = 2 ppb), a rapid response time (< or = 5 seconds) and specific selectivity over other cations under physiological conditions and in live cells according to the confocal fluorescence microscopy experiment.

Fabrication of nanocrystalline ZnWO4 with different morphologies and sizes via hydrothermal route

Abstract ZnWO 4 nanocrystals have been prepared via a hydrothermal route, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy. The size and morphology of ZnWO 4 nanocrystals were found to depend on the reaction temperature and pH. The length of ZnWO 4 nanorod increased with the increase in pH of the hydrothermal solution. An unusual nanoparticle-to-nanorod transformation was observed during the formation of ZnWO 4 nanoparticles at pH 11.0 and 180 °C. Luminescent properties of ZnWO 4 nanocrystals were investigated by photoluminescence (PL) spectroscopy.

Synthesis, structures and properties of nickel(II) and cobalt(II) metal–organic frameworks based on a flexible tricarboxylate ligand H3TTG and different pyridyl-containing ligands

Along with our recent investigations on Ni and Co coordination frameworks of a flexible tripodal ligand of H3TTG (N,N′,N″-1,3,5-triazine-2,4,6-triyltris-glycine), four new complexes {[Ni(HTTG)(4,4′-bpy)(H2O)3]·(H2O)2}n (1), {[Ni2(HTTG)2(bpe)2(H2O)]·(H2O)6}n (2), {[Co2(HTTG)2(bpe)2(H2O)]·(H2O)6}n (3) and {[Co3(TTG)2(bpe)2]·(H2O)2}n (4) were hydrothermally synthesized through reactions of this ligand with different pyridyl-containing ligands {4,4′-bpy (4,4-bipyridine), bpe [1,2-bi(4-pyridyl)ethane]}, respectively. Due to various coordination modes and conformations of the flexible tricarboxylate ligand and pyridyl-containing coligands, these complexes exhibit structural and dimensional diversity. Complex 1 shows a unique 1D chain bridged by the R22(8) hydrogen bonds between the carboxylate groups, the triazine rings, and hydrogen-bonded networks of the solvent water molecules as well. Complexes 2 and 3 are isomorphous and both exhibit special 2D (8,2)-connected double-layer structures with two kinds of 1D channels constructed by the coordination bonds and hydrogen bonding interactions, respectively. Complex 4 features a 3-D network with scarce (8,3)-connected rutile-related topology with a Schlafli symbol (42,622,7,83)(4,62)2 based on secondary building units (SBUs) of linear cobalt clusters [Co3(CO2)4]2−. Significantly, with increasing flexibility of the pyridyl-containing coligands, these corresponding complexes become more and more complicated. In addition, their physical properties such as thermal, XPRD, and magnetism have also been investigated.