Mono- and Dinuclear d(10) Metal Complexes of Hexakis(3,5-dimethylpyrazolyl)cyclotriphosphazene. Synthesis, Structures, and Unusual Solution Dynamic Behavior

Synthesis, structures, and unusual solution dynamic processes of d(10) metal complexes of hexakis(3,5-dimethylpyrazolyl)cyclotriphosphazene (L) are reported. Reaction systems with three MX(n):L mole ratios (MX(n) = d(10) metal halide) in CH(2)Cl(2) have resulted in the formation of [ICu(&mgr;,eta(3),eta(3)-L)CuI] (1), [Cl(2)Zn(&mgr;,eta(2),eta(3)-L)ZnCl(2)] (2), [Cl(2)Cd(&mgr;,eta(3),eta(3)-L)CdCl(2)] (3), and [(eta(3)-L)HgCl(2)] (4). These compounds were characterized by single crystal X-ray diffraction studies, and crystallographic data are given in the order of compound: crystal system; space group; unit cell parameters; Z; unique data (I > 2sigma(I)); R(1). 1.0.5CH(2)Cl(2): monoclinic; P2(1)/c; a = 8.268(4) ?; b = 22.365(5) ?; c = 23.325(8) ?, beta = 93.06(1) degrees; 4; 5736; 4.82. 2.CH(3)CN: monoclinic; P2(1)/c; a = 17.021(3) ?; b = 12.161(2) ?; c = 23.608(5) ?; beta = 107.72(1) degrees; 4; 5469; 3.16. 3.CH(2)Cl(2): monoclinic; P2(1)/n; a = 18.585(5) ?; b = 17.585(4) ?; c = 14.404(3) ?; beta = 102.71(2) degrees; 4; 3814; 3.65. The structure of 4 was attempted but resulted in data of low precision. Reaction of L with CuI and ZnCl(2) in an equimolar ratio afforded [ICu(&mgr;,eta(3),eta(3)-L)ZnCl(2)] (5) which crystallizes in monoclinic space group P2(1)/n with a = 22.876(5) ?, b = 21.594(4) ?, c = 9.177(2) ?, beta = 93.54(2) degrees, Z = 4, and R(1) = 7.00 for 3806 (I > 2sigma(I)) data. In all cases, metal halide centers except the Td zinc site in 2 are coordinated by L via a kappa(3)N binding core consisting of two nongeminal pyrazolyl nitrogen atoms and one phosphazene ring nitrogen atom. The eta(2)-N(2) coordination in 2 involves two geminal pyrazolyl nitrogen atoms. Factors which govern the nuclearity of the complex were partially demonstrated. The intermetallic distances in dinuclear metallophosphazenes range from 6.790 to 7.195 ?. The solution behavior of five compounds was studied by variable temperature (31)P{(1)H}, (1)H, and (113)Cd FT NMR spectroscopy. Compounds 1 and 4 are associated with fluxional motions involving A(2)B low-temperature limit spectrum while compounds 2 and 5 show solvent-dependent dynamic processes with ABX and A(2)B low-temperature limit spectral patterns. Compounds 3 constitutes a fluxional system involving three A(2)B species. Accounts of solution NMR spectra were attempted by using PANIC, by assuming the formation of new solution metallophosphazene species and by considering several types of dynamic processes such as a ring-around type hopping motion for the kappa(3)N metal site, a Td conformational change for the geminal pyrazolyl kappa(2)N metal site, and a wigwag motion for the nongeminal pyrazolyl kappa(2)N metal unit.     

Structural and Functional Analysis of the Pyridoxal Phosphate Homeostasis Protein YggS from Fusobacterium nucleatum

Pyridoxal 5′-phosphate (PLP) is the active form of vitamin B6, but it is highly reactive and poisonous in its free form. YggS is a PLP-binding protein found in bacteria and humans that mediates PLP homeostasis by delivering PLP to target enzymes or by performing a protective function. Several biochemical and structural studies of YggS have been reported, but the mechanism by which YggS recognizes PLP has not been fully elucidated. Here, we report a functional and structural analysis of YggS from Fusobacterium nucleatum (FnYggS). The PLP molecule could bind to native FnYggS, but no PLP binding was observed for selenomethionine (SeMet)-derivatized FnYggS. The crystal structure of FnYggS showed a type III TIM barrel fold, exhibiting structural homology with several other PLP-dependent enzymes. Although FnYggS exhibited low (<35%) amino acid sequence similarity with previously studied YggS proteins, its overall structure and PLP-binding site were highly conserved. In the PLP-binding site of FnYggS, the sulfate ion was coordinated by the conserved residues Ser201, Gly218, and Thr219, which were positioned to provide the binding moiety for the phosphate group of PLP. The mutagenesis study showed that the conserved Ser201 residue in FnYggS was the key residue for PLP binding. These results will expand the knowledge of the molecular properties and function of the YggS family.     

Evaluation of interfacial toughness curve of bimaterial in submicron scale

A novel method combining the experimental data at only two different mixed mode fractures and an empirical interface toughness function has been proposed to establish the interfacial toughness function of a bimaterial in submicron scale. The modified four-point bend specimen was used in experiment to evaluate the first type of mixed mode fracture, while the sandwiched cantilever specimen was employed to get the second one. An empirical interface toughness function reflecting quite accurately the delamination behavior was adopted as a typical one. The obtained results investigated that the proposed method could be used to calibrate not only the interfacial fracture criteria at pure modes but also at any mixed mode fracture of bimaterials in submicron scale.     

Dimesogenic liquid crystal consisting of cholesterol and Schiff base moieties: dependence of LC properties on the spacer length and fluorination of the alkoxy tails

The liquid crystalline properties of two series of non‐symmetric liquid crystal dimers consisting of cholesterol and Schiff base moieties interconnected by ω‐oxyalkanoyl spacers of varying length are compared: one series (SBOC‐ n ) carry the octyloxy tail on the Schiff base mesogen, and the other (SBOF‐ n ) a perfluoroheptylmethyloxy tail. In general, compounds with the fluorinated alkoxy tail exhibited mesophases over a much wider temperature range than those with the alkoxy tail. The latter series favoured the formation of more diverse mesophases than the former. SBOC‐4, ‐5 and ‐7, and SBOF‐4, ‐5 and ‐10 formed the chiral smectic C phase.     

Improved Compatibility of Styrene-Maleic Anhydride Copolymer/Polyethylene Blends Through Reactive Mixing

Abstract

To improve the compatibility of styrene-maleic anhydride copolymer/low density polyethylene (SMA/LDPE) blends, LDPE grafted with 2-hydroxyethyl methacrylate-isophorone diisocyanate (LDPE-g-HI) was prepared and blended with SMA of which anhydride was converted to carboxylic acid (SMAAc). The infrared spectra of LDPE-g-HI established the presence of isocyanate group. In the blend morphology, some adhesions between the two phases and much finer dispersions were observed in the SMAAc/LDPE-g-HI blends, indicating that chemical reactions took place during the melt blending. The lower heat capacity change at the glass transition temperature demonstrated that chemical bonds were produced in the SMAAc/LDPE-g-HI blends. From the results of the rheological test, it was found that strong positive deviation from the mixing rule occurred in viscosity for the SMAAc/LDPE-g-HI blends, concerning with good adhesion and finer dispersions. In the measurement of tensile property, the improved mechanical properties for the SMAAc/LDPE-g-HI blends were shown.     

Perfect controlled joint remote state preparation independent of entanglement degree of the quantum channel

We construct a quantum circuit to produce a task-oriented partially entangled state and use it as the quantum channel for controlled joint remote state preparation. Unlike most previous works, where the parameters of the quantum channel are given to the receiver who can accomplish the task only probabilistically by consuming auxiliary resource, operation and measurement, here we give them to the supervisor. Thanks to the knowledge of the task-oriented quantum channel parameters, the supervisor can carry out proper complete projective measurement, which, combined with the feed-forward technique adapted by the preparers, not only much economizes (simplifies) the receiver's resource (operation) but also yields unit total success probability. Notably, such apparent perfection does not depend on the entanglement degree of the shared quantum channel. Our protocol is within the reach of current quantum technologies.     

Unexpected formation of dinaphthoaza-17-crown-5 ether containing γ-aminopiperidine subunit

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