Synthesis,Structure, and Stability of Lithium Arylphosphanidyl-diarylphosphane Oxide

The reaction of LiP(H)Tipp ( 2a ) and KP(H)Tipp ( 2b , Tipp = C₆H₂-2,4,6-iPr₃), which are accessible via metalation of Tipp-PH₂ ( 1 ), with bis(4-tert-butylphenyl)phosphinic chloride yields Tipp-P=P(OM)Ar₂ [M = Li ( 3a ) and K ( 3b )]. These complexes show characteristic chemical ³¹P shifts and large ¹J_PP coupling constants. These compounds degrade with elimination of the phosphinidene Tipp-P: and the alkali metal diarylphosphinites M–O–PAr₂ [M = Li ( 4a ) and K ( 4b )]. The phosphinidene forms secondary degradation products (like the meso and R,R/S,S-isomers of diphosphane Tipp-P(H)–P(H)Tipp ( 5 ) via insertion into a P–H bond of newly formed Tipp-PH₂), whereas the crystallization of [Tipp-P=P(OLi)Ar₂ · LiOPAr₂ · LiCl · 2Et₂O]₂ (i.e. [ 3a·4a· LiCl · 2Et₂O]₂) succeeds from diethyl ether. The metathesis reactions of LiP(SiiPr₃)Tipp and LiP(SiiPr₃)Mes (Mes = C₆H₂-2,4,6-Me₃) with Ar₂P(O)Cl yield Ar*-P=P(OSiiPr₃)Ar₂ (Ar* = Mes, Tipp) which degrade to Ar₂POSiiPr₃ and other secondary products.     

Carbene stabilization by aryl substituents. Is bigger better?

The geometries and relative stabilities of the singlet and triplet states of phenyl- (Cs), diphenyl- (C2), 1-naphthyl- (Cs), di(1-naphthyl)- (C2), and 9-anthryl-substituted (Cs) carbenes were investigated at the B3LYP/6-311+G(d,p) + ZPVE level of density functional theory. The singlet-triplet energy separations (DeltaEST), 2.7, 2.9, 3.4, 3.7, and 5.7 kcal/mol, respectively, after including an empirical correction (2.8 kcal/mol) based on the error in the computed singlet-triplet gap for methylene versus experiment, are in good agreement with available experimental values. Consistent with literature reports, triplet di(9-anthryl)carbene has a linear, D2d symmetrical, allene structure with 1.336 A C=C bond lengths and considerable biradical character. B3LYP favors such cumulene biradical structures and triplet spin states and predicts a large (>15 kcal/mol) "di(9-anthryl)carbene" singlet-triplet (biradical) energy gap. The resonance stabilization of both singlet and triplet carbenes increases modestly with the size of the arene substituent and overall, (di)arylcarbenes, both singlet and triplet, are better stabilized by bigger substituents. For example, methylene is stabilized more by a naphthyl than a phenyl group (singlets, 26.6 versus 24.4; and triplets, 20.9 versus 18.1 kcal/mol, respectively). The carbene geometries are affected by both steric effects and arene-carbene orbital interactions (sigma-p and p-pi). For instance, the central angles at the carbene are widened by a second arene group, which leads to increased s-character and shorter carbene bond lengths (i.e., C-C, C-H). In general, the aromaticity of the substituted rings in triplet carbenes is most affected by the presence of the unpaired electrons.     

Crystallographic and vibrational spectroscopic studies of octakis(DMSO)lanthanoid(III) iodides

The octakis(DMSO) (DMSO = dimethylsulfoxide) neodymium(III), samarium(III), gadolinium(III), dysprosium(III), erbium(III), and lutetium(III) iodides crystallize in the monoclinic space group P21/n (No. 14) with Z = 4, while the octakis(DMSO) iodides of the larger lanthanum(III), cerium(III), and praseodymium(III) ions crystallize in the orthorhombic space group Pbca (No. 61), Z = 8. In all [Ln(OS(Me2)8]I3 compounds the lanthanoid(III) ions coordinate eight DMSO oxygen atoms in a distorted square antiprism. Up to three of the DMSO ligands were found to be disordered and were described by two alternative configurations related by a twist around the metal-oxygen (Ln-O) bond. To resolve the atomic positions and achieve reliable Ln-O bond distances, complete semirigid DMSO molecules with restrained geometry and partial occupancy were refined for the alternative sites. This disorder model was also applied on previously collected data for the monoclinic octakis(DMSO)yttrium(III) iodide. At ambient temperature, the eight Ln-O bond distances are distributed over a range of about 0.1 A. The average value increases from Ln-O 2.30, 2.34, 2.34, 2.36, 2.38, 2.40 to 2.43 A (Ln = Lu, Er, Y, Dy, Gd, Sm, and Nd) for the monoclinic [Ln(OSMe2)8]I3 structures, and from 2.44, 2.47 to 2.49 A (Ln = Pr, Ce, and La) for the orthorhombic structures, respectively. The average of the La-O and Nd-O bond distances remained unchanged at 100 K, 2.49 and 2.43 A, respectively. Despite longer bond distances and larger Ln-O-S angles, the cell volumes are smaller for the orthorhombic structures (Ln = Pr, Ce, and La) than for the monoclinic structure with Ln = Nd, showing a more efficient packing arrangement. Raman and IR absorption spectra for the [Ln(OS(CH3)2)8]I3 (Ln = La, Ce, Pr, Nd, Gd, Tb, Dy, Er, Lu, and Y) compounds, also deuterated for La and Y, have been recorded and analyzed by means of normal coordinate methods. The force constants for the Ln-O and S-O stretching modes in the complexes increase with decreasing Ln-O bond distance and show increasing polarization of the bonds for the smaller and heavier lanthanoid(III) ions.     

Analysis of Purkinje images as an effective method for estimation of intraocular lens implant location in the eyeball

The implantation of an artificial intraocular lens (IOL) into a capsular bag in place of an extracted natural, but nontransparent lens is a standard therapy method in the case of cataract. Any decentration or tilt of the IOL can cause a deterioration of the retinal image quality, thus decreasing the vision quality. The analysis of the relative position of Purkinje images being a reflection of the point light source from the refracting surfaces of the eyeball determines the location of IOL inside the eye and thus enables to state its wrong or correct location. The paper describes the Purkinje experimental setup consisting of an illuminator (several infrared LEDs arranged in a circle), an imaging telecentric lens and image recording CCD camera and reports details of the system calibration The usefulness of the experimental setup has been proven both in laboratory conditions using artificial model of the eyeball and in measurements on human subjects. Simulations of the retinal image with different decentrations or tilts are shown.     

Variety of mesophases in compounds with an increasing number of lactate units in the chiral chain

Liquid-crystalline compounds with different numbers of lactate units, n, in the chiral part were synthesised and mesomorphic properties studied. Physical properties were compared with respect to n. In the compound with one lactate unit in the chiral part the TGBA–TGBC–SmC* phase sequence was detected. For two lactate units the antiferroelectric SmC*_A phase occurs. Finally, three-lactate material exhibits the tilted hexatic SmI*(F*) phase below the ferroelectric SmC* phase. Dielectric spectroscopy and spontaneous tilt and polarisation were measured. For the three-lactate compound the temperature dependences were analysed in the vicinity of the SmC*–hexatic phase transition, and these properties compared with the theoretically predicted behaviour.     

Glass Transition Temperature Improvement for Polychloroprene by One-Step ATRP Reaction

Polymethyl methacrylate (PMMA) polymer chains were grafted on neoprene W (NW) by a one-step ATRP reaction. The thermal properties of the products were analyzed by DSC. Improvement of T _g was a result of the PMMA grafted chains. Also, the melting point (T _m ) changed from 42°C for NW to 142°C for modified NW. Using different solvents for the resulting copolymers, aggregates were obtained. Phase separation was influenced by the grafting degree of PMMA and the employed solvent. The copolymers were analyzed by GPC, FT-IR, DSC, and SEM.     

THE METASTABLE PARTIALLY POSITIVELY CHARGED Se6 MOLECULE: PREPARATION,CHARACTERISATION AND X-RAY CRYSTAL STRUCTURE OF [Ag2(Se6)(SO2)2][Sb(OTeF5)6]2, [Ag2Se6][AsF6]2 AND [AgSe6][Ag2(SbF6)3]

Reactions designed to give Se₆[Sb(OTeF₅)₆]₂ by the reaction of Se₂Br₂, 4Se, and 2Ag[Sb(OTeF₅)₆] lead to products that include [Ag₂(Se₆)(SO₂)₂][Sb(OTeF₅)₆]₂(1). The distorted cubic (Ag₂Se₆ ²⁺) _n consists of a Se₆ molecule bicapped by two silver cations (local D_3d sym.). Reactions of AgMX₆ (M = As, Sb) with selenium in liquid SO₂ yielded crystals of [Ag₂Se₆][AsF₆]₂ (2) and [AgSe₆][Ag₂(SbF₆)₃] (3). Both salts contain stacked arrays of [AgSe₆]⁺ half-sandwich cationic units. [Ag₂Se₆][AsF₆]₂ in addition contains stronger, linear Se─Ag─Se horizontal linkages between the vertically stacked cationic columns. [AgSe₆][Ag₂(SbF₆)₃] features a remarkable three-dimensional [Ag₂(SbF₆)₃]^? anion held together by strong Sb─F···Ag contacts between component Ag⁺ and SbF₆ ^? ions. Hexagonal channels through this honeycomb-like anion are filled by the stacked [AgSe₆ ⁺]_x.     

Electrophoretic deposition of poly(3-decylthiophene) onto gold-mounted cadmium selenide nanorods

Molecular mechanisms of electrophoretic deposition (EPD) of poly(3-decylthiophene) (P3DT) molecules onto vertically aligned cadmium selenide arrays have been studied using large-scale, nonequilibrium molecular dynamics (MD), in the absence and presence of static external electric fields. The field application and larger polymer charges accelerated EPD. Placement of multiple polymers at the same lateral displacement from the surface reduced average deposition times due to "crowding", giving monolayer coverage. These findings were used to develop and validate Brownian dynamics simulations of multilayer polymer EPD in scaled-up systems with larger inter-rod spacings, presenting a generalized picture in qualitative agreement with random sequential adsorption.     

Pipette-tip selective extraction of glycoproteins with lectin modified gold nano-particles on a polymer monolithic phase

The in situ preparation of ethylene dimethacrylate porous polymer monoliths within 20 μL polypropylene pipette tips, bound via surface grafted methacrylate anchor sites, is reported. Gold nano-particles (AuNPs) were immobilised onto the monolith pore surface utilising azlactone chemistry and coverage verified using field emission scanning electron microscopy. Erythrina cristagalli lectin (ECL) was immobilised upon the attached AuNPs via a bio-functional linker. The ECL-modified tip was successfully applied for the enrichment of galactosylated protein (desialylated transferrin) versus a non-galactosylated protein (ribonuclease B) due to the specificity of ECL. Reversed-phase capillary HPLC was used to validate the efficiency and selectivity of the developed micro-extraction phase which resulted in an increase in extraction recovery of ～95% due to the AuNP enhanced surface area. Further specificity of the ECL-modified tip was demonstrated with a complex mixture of non-glycosylated and glycosylated proteins with differing terminal sugar structures. Finally, the lectin affinity phase was applied to a galactosylated glycoproteins spiked Escherichia coli cell lysate to successfully demonstrate matrix tolerance.     

Influence of nanocrystalline structure and composition on hardness of thin films based on TiO<Subscript>2</Subscript>

In this work, the influence of Tb-doping on structure, and especially hardness of nanocrystalline TiO₂ thin films, has been described. Thin films were formed by a high-energy reactive magnetron sputtering process in a pure oxygen atmosphere. Undoped TiO₂-matrix and TiO₂:Tb (2 at. % and 2.6 at. %) thin films, had rutile structure with crystallite sizes below 10 nm. The high-energy process produces nanocrystalline, homogenous films with a dense and close packed structure, that were confirmed by X-ray diffraction patterns and micrographs from a scanning electron microscope. Investigation of thin film hardness was performed with the aid of a nanoindentation technique. Results of measurements have shown that the hardness of all manufactured nanocrystalline films is above 10 GPa. In the case of undoped TiO₂ matrix, the highest hardness value was obtained (14.3 GPa), while doping with terbium results in hardness decreasing down to 12.7 GPa and 10.8 GPa for TiO₂:(2 at. % Tb) and TiO₂:(2.6 at. % Tb) thin films, respectively. Incorporation of terbium into TiO₂-matrix also allows modification of the elastic properties of the films.