Preparation and characterization of acrylic‐based black particles of poly(methyl methacrylate‐co‐ethylene glycol dimethacrylate) by dispersion polymerization for electrophoretic displays

Ultrafine black particles, ranging in diameter from 1 to 3 μm, were prepared by dispersion polymerization in a methanol/water mixture with vinyl monomers, nonpolymerizable Sudan black B dyes, and fluorescein isothiocyanate labeled charge control additives. Both the ratio of the methanol to the water dispersion medium and the polymeric stabilizer concentration had significant effects on the particle size. The important role of the stabilizer concentration lay in the particle formation step, during which it determined the particle stability and final particle size. These could affect the extent of the aggregation of nuclei by changing the adsorption rate of the stabilizer and the viscosity of the dispersion medium, resulting in smaller particles. The fluorescent‐labeled charge control additives strongly affected the electrophoretic mobility. A small concentration of fluorescent‐labeled charge control additives increased the electrophoretic mobility. However, a further addition reduced the electrophoretic mobility of the polymer particles. The concentration dependence of the fluorescent‐labeled charge control additives on the deposition behavior in the polymer particles was successfully imaged and thereafter quantified by image analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5608–5616, 2004     

Investigation of novel mediators for a glucose biosensor based on metal picolinate complexes

The metal complexes [Os(byp)(2)(pic)](+) and [Ru(byp)(2)(pic)](+) where byp is 2,2'-bipyridine and HPic is o-picolinic acid were synthesised and characterised using spectroscopic and electrochemical techniques. These complexes were then evaluated as mediators for a glucose oxidase (GOx)-based biosensor. Results demonstrate the electrocatalytic behaviour of both metal couples towards regeneration of the flavoprotein GOx (FADH(2)) group, when co-immobilised with glucose oxidase. Surface immobilisation was achieved by potential cycling in aqueous solutions of the metal complexes at a glucose oxidase (GOx)/Nafion modified electrode. This proved successful in terms of catalytic efficiency and stability of redox sites. Kinetic parameters associated with both enzymatic and mediator reactions were estimated and the stability/performance properties of the sensor were tested.     

Three-coordinate [Cu(II)X(3)](-) (X=Cl, Br), trapped in a molecular crystal

Mixtures of [Ph(3)PNPPh(3)](+)Cl(-) with CuBr(2) (or CuBr(2)+CuCl(2)) in ethanol/dichloromethane yield crystals containing three-coordinate copper(II) with mixed chloride and bromide ligands, namely [Ph(3)PNPPh(3)](+)[CuCl(0.9)Br(2.1)](-) (1) and [Ph(3)PNPPh(3)](+)[CuCl(2.4)Br(0.6)](-) (2). The trigonal-planar coordination of copper(II) is angularly distorted but unambiguous, as there is no other halide ligand within 6.7 A of the copper atom. Density functional theory (DFT) calculations on planar [CuClBr(2)](-) show that the energy surface for angle bending is very soft. Crystallisation in the presence of CH(3)CN yields [Ph(3)PNPPh(3)](+)[CuCl(0.7)Br(2.3)(NCCH(3))](-) (3), in which there is additional secondary coordination by NCCH(3) (Cu-N 2.44 A). DFT calculations of the potential energy surface for this secondary coordination show that it is remarkably flat (<3 kcal mol(-1) for a variation of Cu-N by 0.8 A). The crystal packing in 1, 2 and 3, which involves multiple phenyl embraces between [Ph(3)PNPPh(3)](+) ions and numerous C-H...Cl and C-H...Br motifs, is associated with intermolecular energies that are larger than the variations in intramolecular energies. For reference, the crystal structures of [Ph(3)PNPPh(3)(+)](2)[Cu(2)Cl(6)](2-) (4) and [Ph(3)PNPPh(3)(+)](2)[Cu(2)Br(6)](2-) (5) are described. We conclude 1) that three-coordinate copper(II) with monatomic halide ligands, although uncommon, can be regarded as normal, 2) that steric control by ligands is not necessary to enforce three-coordination, 3) that a hydrophobic aryl environment stabilises [Cu(Cl/Br)(3)](-), and 4) that the energy change in the transition from three- to four-coordinate copper(II) is very small (ca 5 kcal mol(-1)).     

Use of the tubulin bound paclitaxel conformation for structure-based rational drug design

A new computational docking protocol has been developed and used in combination with conformational information inferred from REDOR-NMR experiments on microtubule bound 2-(p-fluorobenzoyl)paclitaxel to delineate a unique tubulin binding structure of paclitaxel. A conformationally constrained macrocyclic taxoid bearing a linker between the C-14 and C-3'N positions has been designed and synthesized to enforce this "REDOR-taxol" conformation. The novel taxoid SB-T-2053 inhibits the growth of MCF-7 and LCC-6 human breast cancer cells (wild-type and drug resistant) on the same order of magnitude as paclitaxel. Moreover, SB-T-2053 induces in vitro tubulin polymerization at least as well as paclitaxel, which directly validates our drug design process. These results open a new avenue for drug design of next generation taxoids and other microtubule-stabilizing agents based on the refined structural information of drug-tubulin complexes, in accordance with typical enzyme-inhibitor medicinal chemistry precepts.     

Physicochemical properties of enhanced-fluidity liquid solvents

Enhanced fluidity (EF) liquid mixtures are advantageous as mobile phases for the separation of moderate to polar compounds in liquid chromatography (reversed-phase, normal, size exclusion, size exclusion, and chiral separations). The low viscosities and high diffusivities of EF mixtures allow highly efficient separations to be achieved in a small amount of time. The best use of enhanced-fluidity liquids is only possible when their physicochemical properties are known. Herein, the techniques used to measure the physicochemical properties (phase diagram, diffusivity, solvent strength and pH) of EF liquids are described. For each technique, the experiment design and the care necessary to insure the quality of the collected data are described. Finally, the impact of the measured physicochemical properties on the chromatography is also highlighted.     

Three 4‐amino­quinolines of anti­malarial interest

The structures of three compounds with potential anti­malarial activity are reported. In N,N‐diethyl‐N′‐(7‐iodo­quinolin‐4‐yl)ethane‐1,2‐diamine, C₁₅H₂₀IN₃, (I), the mol­ecules are linked into ribbons by N—H⋯N and C—H⋯N hydrogen bonds. In N‐(7‐bromo­quinolin‐4‐yl)‐N′,N′‐diethyl­ethane‐1,2‐diamine dihydrate, C₁₅H₂₀BrN₃·2H₂O, (II), two amino­quino­line mol­ecules and four water mol­ecules form an R₅⁴(13) hydrogen‐bonded ring which links to its neighbours to form a T5(2) one‐dimensional infinite tape with pendant hydrogen bonds to the amino­quinolines. The phosphate salt 7‐chloro‐4‐[2‐(diethyl­ammonio)ethyl­amino]quinolinium bis­(dihydrogen­phosphate) phospho­ric acid, C₁₅H₂₂ClN₃²⁺·2H₂PO₄⁻·H₃PO₄, (III), was prepared in order to establish the protonation sites of these compounds. The phosphate ions form a two‐dimensional hydrogen‐bonded sheet, while the amino­quino­line cations are linked to the phosphates by N—H⋯O hydrogen bonds from each of their three N atoms. While the conformation of the quinoline region hardly varies between (I), (II) and (III), the amino side chain is much more flexible and adopts a significantly different conformation in each case. Aromatic π–π stacking inter­actions are the only supramolecular inter­actions seen in all three structures.     

Palladium salicylaldimine complexes containing boronate esters

Reactions of salicylaldehydes with boronate ester derivatives of aniline have been examined. Addition of these Schiff base ligands to palladium acetate or Na₂PdCl₄ afforded novel boron-containing trans-bis(N-arylsalicylaldiminato) palladium complexes.Condensation of salicylaldehyde (2-HOC₆H₄C(O)H) with H₂NC₆H₄Bpin (pin=1,2-O₂C₂Me₄) afforded the boron-containing Schiff bases, 2-HOC₆H₄C(H)=NC₆H₄Bpin (1–3a). Similar reactivity with 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde gave the corresponding Schiff bases (1-3b) and (1-3c), respectively. Reaction of Schiff bases (2) and (3) with palladium acetate or Na₂PdCl₄ afforded complexes of the type PdL₂ (4,5), where L=deprotonated Schiff base. The molecular structure of the nitro-salicylaldehyde 4-Bpin palladium complex (5b) was characterized by an X-ray diffraction study. All new palladium compounds have been characterized fully and tested for their antifungal activity against Aspergillus niger and Aspergillus flavus.     

Enantioselective oxidation of sulfides with hydrogen peroxide catalyzed by vanadium complex of sterically hindered chiral Schiff bases

Sterically hindered chiral Schiff base ligands 4a-d were prepared from an aldehyde derived from BINOL. The vanadium complexes of the ligands catalyze an efficient, enantioselective H₂O₂-promoted sulfoxidation of alkyl aryl sulfides, and enantioselectivities as high as 98-99% ee are observed in the sulfoxidation of benzyl aryl sulfides.     

Recoil energy distributions for dissociation of the van der Waals molecule p-difluorobenzene-Ar with 450-3000 cm(-1) excess energy

Velocity map imaging has been used to measure the distributions of translational energy released in the dissociation of p-difluorobenzene-Ar van der Waals complexes from the 5(1), 3(1), 5(2), 3(1)5(1), 5(3), 3(2), and 3(2)5(1) states. These states span 818-3317 cm(-1) of vibrational energy and correspond to a range of energies above dissociation of 451-2950 cm(-1). The translational energy release (recoil energy) distributions are remarkably similar, peaking at very low energy (10-20 cm(-1)) and decaying in an exponential fashion to approach zero near 300 cm(-1). The average translational energy released is small, shows no dependence on the initial vibrational energy, and spans the range 58-72 cm(-1) for the vibrational levels probed. The average value for the seven levels studied is 63 cm(-1). The low fraction of transfer to translation is qualitatively in accord with Ewing's momentum gap model [G. E. Ewing, Faraday Discuss. 73, 325 (1982)]. No evidence is found in the distributions for a high energy tail, although it is likely that the experiment is not sufficiently sensitive to detect a low fraction of transfer at high translational energies. The average translational energy released is lower than has been seen in comparable systems dissociating from triplet and cation states.