Colin Brennan

Synthesis of gold nanoparticles within a supramolecular gel-phase network

Gold nanoparticles with diameters of ca. 13 nm were synthesised by UV irradiation of a supramolecular organogel into which HAuCl4 and tetraoctylammonium bromide had been diffused-the gel network plays an essential role in nanoparticle stabilisation.

Dendron-stabilised gold nanoparticles: generation dependence of core size and thermal stability

L-Lysine based dendrimers containing a disulfide moiety at the core were synthesized. These novel ligands were used to stabilize Au nanoparticles via a one-phase chemical reduction method. The size of the resultant nanoparticles was found to decrease with increasing dendritic generation. Furthermore, the thermal stability of the nanoparticles in solution was shown to be controlled by the extent of branching in the protecting dendritic shell.

The application of frequency-domain Fluorescence Lifetime Imaging Microscopy as a quantitative analytical tool for microfluidic devices

We describe the application of wide-field frequency domain Fluorescence Lifetime Imaging Microscopy (FLIM) to imaging in microfluidic devices. FLIM is performed using low cost, intensity modulated Light Emitting Diodes (LEDs) for illumination. The use of lifetime imaging for quantitative analysis within such devices is demonstrated by mapping the molecular diffusion of iodide ions across a microchannel.

Synthesis, Characterisation and Reactivity of Copper(I) Amide Complexes and Studies on Their Role in the Modified Ullmann Amination Reaction

A series of copper(I) alkylamide complexes have been synthesised; copper(I) dicyclohexylamide (1), copper(I) 2,2,6,6-tetramethylpiperidide (2), copper(I) pyrrolidide (3), copper(I) piperidide (4), and copper(I) benzylamide (5). Their solid-state structures and structures in [D6]benzene solution are characterised, with the aggregation state in solution determined by a combination of DOSY NMR spectroscopy and DFT calculations. Complexes 1, 2 and 4 are shown to exist as tetramers in the solid state by X-ray crystallography. In [D6]benzene solution, complexes 1, 2 and 5 were found by using 1H DOSY NMR to exist in rapid equilibrium between aggregates with average aggregation numbers of 2.5, 2.4 and 3.3, respectively, at 0.05 m concentration. Conversely, distinct trimeric, tetrameric and pentameric forms of 3 and 4 were distinguishable by one-dimensional 1H and 1H DOSY NMR spectroscopy. Complexes 3–5 are found to react stoichiometrically with iodobenzene, in the presence or absence of 1,10-phenanthroline as an ancillary ligand, to give arylamine products indicative of their role as potential intermediates in the modified Ullmann reaction. The role of phenanthroline has also been explored both in the stoichiometric reaction and in the catalytic Ullmann protocol.

Evidence for anisotropy in chlorine/nitrogen interactions in the cyanuric chloride crystal structure

Abstract The non-linearity of some of the chlorine/nitrogen intermolecular interactions upon which the known crystal structure of cyanuric chloride depends is evidence for the inadequacy of current isotropic models of interatomic potentials used for crystal packing predictions.

Mechanism of solid|liquid interfacial reactions. The reactive dissolution of p-chloranil in aqueous solution as studied by the channel flow cell with electrochemical detection and atomic force microscopy

Abstract A quantitative study of the hydrolytic dissolution of solid p-chloranil at alkaline pH using a combination of the channel flow cell and in situ atomic force microscopy measurements shows that the dissolution is driven by reaction of the substrate with hydroxide ions at, or very close to, the dissolving surface. The dissolution rate equation, deduced from the channel flow cell for single crystals of p-chloranil, is rate/mol cm −2 s −1 = 3.8 × 10 −7 [OH − ] 0 where [OH − ] 0 /M is the hydroxide ion concentration adjacent to the solid surface. An analogous rate law is derived for pressed pellet substrates. The novel application of the atomic force microscope to make absolute measurements of surface averaged dissolution rates is described. Comparison with the independent channel flow cell data reveals good mechanistic agreement and consistency of rate constants provided it is recognised that a thick stagnant diffusion layer can be present under the usual conditions employed for AFM.

Comparative solubilisation of potassium carbonate, sodium bicarbonate and sodium carbonate in hot dimethylformamide: application of cylindrical particle surface-controlled dissolution theory.

A surface-controlled dissolution of cylindrical solid particles model is applied to potassium carbonate, sodium bicarbonate and sodium carbonate in dimethylformamide at elevated temperatures. Previously published data for the dissolution of potassium carbonate is interpreted assuming a cylindrical rather than a spherical shape of the particles, the former representing a closer approximation to the true shape of the particles as revealed by scanning electron microscopy. The dissolution kinetics of sodium carbonate and sodium bicarbonate in dimethylformamide at 100 degrees C were investigated via monitoring of the deprotonation of 2-cyanophenol with dissolved solid to form the 2-cyanophenolate anion that was detected with UV-visible spectroscopy. From fitting of experimental results to theory, the dissolution rate constant, k, for the dissolutions of potassium carbonate, sodium bicarbonate and sodium carbonate in dimethylformamide at 100 degrees C were found to have the values of (1.0 +/- 0.1) x 10(-7) mol cm(-2) s(-1), (5.5 +/- 0.3) x 10(-9) mol cm(-2) s(-1) and (9.7 +/- 0.8) x 10(-9) mol cm(-2) s(-1), respectively.

Voltammetric study of the reaction of the 2-cyanophenoxide anion with carbon dioxide in dimethylformamide

The electrochemical reduction of 2-cyanophenol was studied in dimethylformamide (DMF) at a platinum microdisk electrode in the absence of carbon dioxide and with saturations of 10% and 100% carbon dioxide. Upon introduction of carbon dioxide it was inferred that the 2-cyanophenoxide anion, formed after the reduction of 2-cyanophenol and concomitant rapid protonation of the radical anion, reacts with carbon dioxide to form a possible cyanophenoxide–carbon dioxide complex. The latter then undergoes further protonation from the parent 2-cyanophenol. The complex formed undergoes further electrochemical reduction at the platinum electrode, introducing a new voltammetric reduction wave. UV/visible and IR spectroscopic studies confirm these inferences.

The production of tyramine via the selective hydrogenation of 4-hydroxybenzyl cyanide over a carbon-supported palladium catalyst

The selective production of primary amines is a problem that plagues heterogeneously catalysed nitrile hydrogenation reactions. Whilst the target amine tyramine (HOC6H4CH2CH2NH2) is biochemically available through the action of enzymes, synthetic routes to this species are not widely reported. Here, a heterogeneously catalysed method is proposed that utilises a Pd/C catalyst to effect the selective hydrogenation of 4-hydroxybenzyl cyanide within a three-phase reactor. The aforementioned selectivity issues are overcome by adjustment of various experimental parameters (hydrogen supply, agitation rate, temperature, use of an auxiliary agent) that result in improved catalytic performance, such that the desired tyramine salt (tyramine hydrogen sulphate) can be produced in quantitative yield. Accordingly, through consideration of the interconnectivity of hydrogenation and hydrogenolysis processes, a selective synthetic strategy is achieved with the findings suitable for extension to other substrates of this nature.