Grainne Moran

Formation of a fulvene by trimerisation of an alkyne at a rhodium centre; crystal structure of cycloocta-1,5-diene(η5-1,3,6-tri-t-butylfulvene) rhodium hexafluorophosphate

Reaction of [RhCl(1,5-C8H12)]2 with silver hexafluorophosphate in the presence of an excess of 3,3-dimethylbut-1-yne gives cycloocta-1,5-diene(η5-1,3,6-tri-t-butylfulvene) rhodium hexafluorophosphate, which was identified by X-ray crystallography.

Orientation effects in the deuterium NMR spectroscopy of perfluorinated ionomer membranes

Abstract The properties of water in Nafion ® and Dow perflourinated ionomer membranes in their protonated forms were investigated by proton and deuterium NMR spectroscopy. The 2 H quadrupolar splittings were shown to be dependent on the orientation of the membranes in the magnetic field as well as on their water content. The larger quadrupolar splittings found for Nafion are attributed to a greater degree of orientational order compared to the Dow samples. Hydrogen bonding, as evidenced by 1 H and 2 H chemical shifts, was very similar in the two types of membrane for a given relative humidity. The 2 H spin-lattice relaxation times ( T 1 ) were 93 and 109 ms for Nafion and Dow respectively at 300 K and 100% relative humidity, compared to 612 ms for D 2 O in 1:9 D 2 O:H 2 O. The temperature dependence of the T 1 values was similar for the two membranes in the range 280–320 K and activation energies for molecular reorientation were estimated at 22±2 kJ mol -1 , comparable to that for pure water in the same temperature range.

Absorption and magnetic circular dichroism spectra of the compressed copper (II) ion in K2ZnF4

The polarized absorption and magnetic circular dichroism spectra of 1–3% copper(II) doped into the tetragonal host K2ZnF4 are measured over the temperature range 1.8-300 K. Sharp origins for the spin-orbit components of the 2A1g(z2→ 2Eg(xz, yz) transition and accompanying vibrational fine structure are observed. The spectra are interpreted on the basis of doped Cu(II) ions occupying a tetragonally compressed octahedron of six-coordinated fluoride ions. This system presents an excellent opportunity for the study of a highly structured spectrum of a Cu(II) complex with an unusual geometry.

Luminescence decay characteristics of Ru(bpy)2+3 in dilute single crystals and polymer hosts

Abstract Luminescence decay characteristics for Ru(bpy) 2+ 3 doped in dilute single crystals and polymer hosts have been measured in the temperature range 1.5 to 77 K using 1 ms square-pulse excitation from an acousto-optically modulated Ar + laser. Previously observed deviations from single-exponential decay behaviour in experiments using higher-power, short (3 ns) pulse excitation, are shown to be mainly due to sample heating effects. The temperature dependence of the decay times is consistent with luminescence from three states of equal degeneracy, separated by (8±0.5) and (60±5) cm -1 respectively.

Hierarchical surfaces: an in situ investigation into nano and micro scale wettability

Two scales of roughness are imparted onto silicon surfaces by isotropically patterning micron sized pillars using photolithography followed by an additional nanoparticle coating. Contact angles of the patterned surfaces were observed to increase with the addition of the nanoparticle coating, several of which, exhibited superhydrophobic characteristics. Freeze fracture atomic force microscopy and in situ synchrotron SAXS were used to investigate the micro- and nano-wettability of these surfaces using aqueous liquids of varying surface tension. The results revealed that scaling different roughness morphologies result in unique wetting characteristics. It indicated that surfaces with micro, nano or dual scale roughness induced channels for the wetting liquid as per capillary action. With the reduction of liquid surface tension, nano-wetting behaviour differed between superhydrophobic and non-superhydrophobic dual-scale roughness surfaces. Micro-wetting behaviour, however, remained consistent. This suggests that micro- and nano-wetting are mutually exclusive, and that the order in which they occur is ultimately governed by the energy expenditure of the entire system.

Temperature-dependent lifetimes, MCPL and shifts of the luminescence in the materials [Ru(bpy)x(bpy-d8)3-x]2+, x=0–3, in dilute systems

Abstract Luminescence decay kinetics of the title series, measured after quasi-steady-state excitation, are found to be first order under all conditions. The decay rates of the x =1 and 2 partially deuterated complexes are approximately evenly spaced between the x =0 and x =3 values. Luminescence profiles are almost identical for the series, but with the low-temperature x =0 luminescence shifted ≈40 cm −1 to higher energy relative to the x =1, 2, 3 spectra. MCPL magnitudes were found to be unaffected by deuteration. Analysis of the temperature dependence of the lifetimes in poly(vinyl alcohol) indicates an 8.2±0.2 cm −1 lowest energy gap for all four complexes, which is consistent with the zero-phonon line separations in single crystals of the PF 6 salts.

Measurement of gold and sulfur mass fractions in L-cysteine-modified gold nanoparticles by ICP-DRC-MS after acid digestion: validation and uncertainty of results

Measurement of mass fractions of trace element sulfur and main element gold in L-cysteine-modified gold nanoparticles was performed by inductively coupled plasma mass spectrometry with dynamic reaction cell (DRC) technology after aqua regia digestion. Sulfur concentration was measured at m/z 48 as 32S16O+ in a reaction cell with O2 to reduce the effect of polyatomic interferences at m/z 32. Following a study of the main interferences affecting the signal from 32S16O+, optimization of instrument parameters by an experimental design along with an investigation of the effect of aqua regia in matrix on the signal-to-background ratio of 32S16O+ were carried out to improve the detection limit for sulfur. Under the optimum experimental conditions the detection limits were 1.43 μg L−1 for S and 0.033 μg L−1 for Au. 45Sc was selected as the internal standard for measurement of 32S16O+. The presence of Au at high concentrations showed a negligible effect on the intensity of 32S16O+ and 45Sc+ under DRC mode. The method was in-house validated and the combined uncertainty was estimated according to the Guide to the Expression of Uncertainty in Measurement. Preliminary studies show that the method may be transferred to other ICP-MS systems by re-optimizing cell gas flow (e.g. 1.8 mL min−1 used for NexION 300D). X-ray photoelectron spectroscopy confirmed that a self-assembled monolayer of cysteine was formed on the surface of colloidal gold nanoparticles via sulfur-to-gold bonding.

Reactions of co-ordinated ligands. Part 29. The formation of a 1,3-diene at a molybdenum centre by linking of but-2-yne with an alkene; X-ray crystal structures of [Mo(η2-o-Ph2PC6H4CHCH2)(η2-MeC2Me)(η-C5H5)][BF4] and [Mo(NCMe)(η4-o-MeCHCMe–CHCHC6H4PPh2)(η-C5H5)][BF4]

Reaction of [Mo(CO)(η2-RC2R′)2(η-C5H5)][BF4](R = R′= Me; R = H, R′= But) with o-diphenylphosphinostyrene (dpps) in CH2Cl2 affords the alkyne–alkene complex [Mo(dpps)(η2-RC2R′)(η-C5H5)][BF4]. The structure of [Mo(η2-dpps)(η2-MeC2Me)(η-C5H5)][BF4] was established by X-ray crystallography. Crystals are orthorhombic, space group Pna21 with Z= 4 in a unit cell of dimensions a= 22.324(5), b= 9.249(3), c= 14.566(3)A. The structure has been refined to R= 0.040 (R′= 0.041) for 2 228 reflections at 293 K. The molybdenum atom is bonded to an η-C5H5, an η2-bonded but-2-yne, and chelating o-diphenylphosphinostyrene ligands, where the C–C vectors of the co-ordinated alkyne and alkene lie essentially parallel to the Mo–P axis. In refluxing acetonitrile the but-2-yne cation is transformed via C–C bond formation and a 1,3-H shift into a 1,3-diene complex [Mo(NCMe)(η4-MeCHCMe–CHCHC6H4PPh2-o)(η-C5H5)][BF4] identified by X-ray crystallography. Crystals are monoclinic, space group P21/c with Z= 4 in a unit cell of dimensions a= 10.836(2), b= 8.551 (2), c= 30.896(6)A, and β= 94.80(2)°. The structure has been refined to R= 0.029 (R′= 0.030) for 3 828 reflections at 293 K. The cation contains a molybdenum atom bound to an η-C5H5 ligand, an N-bonded acetonitrile, and a ligand formally derived from but-2-yne and o-diphenylphosphinostyrene, which is η4-bonded to the Mo via a 1,3-diene moiety. The co-ordinated acetonitrile is displaced by ButCN, CO, and P(OMe)3 to form the cations [Mo(L)(η4-MeCHCMe–CHCHC6H4PPh2-o)(η-C5H5)][BF4][L = ButCN, CO, or P(OMe)3]. The nitrile-substituted cations exist in solution as a mixture of two conformational isomers, whereas the CO- and P(OMe)3-substituted cations are present in only one isomeric form. The conformations of these species are discussed in terms of frontier molecular orbitals, and the nature of the 1,3-H shift process has been examined using deuterium-labelled o-diphenylphosphinostyrene.

NMR relaxation studies of porous sol-gel glasses

2H relaxation times T1, T1 rho and T2 for D2O in silica sol-gels are used to monitor porosity and surface interactions within the silica framework as a function of aging. Tetramethoxysilane gels are compared with composites containing low levels of poly(vinyl alcohol) (PVA) prepared under acidic conditions. Non-exponential decay of magnetisation in T1 rho and T2 experiments is attributed to the fractal nature of the pore structure.

Magnetic circular dichroism spectroscopy of the hexacyano complexes of Ru(III) and Os(III)

Abstract The UV-Vis absorption and magnetic circular dichroism spectra of (Bu4N)3Ru(CN)6 and (Bu4N)3Os(CN)6 were measured at 4.2 K. The MCD spectra confirm the assignments of the ligand-to-metal charge transfer transitions in these complexes. They also cast doubt on earlier d-d assignments made for Os(CN)63− and Fe(CN)63−. Attempts to measure the intraconfigurational d-d splitting of the 2T2g ground state of (Bu4N)3Ru(CN)6 were unsuccessful. However, the near IR MCD spectrum of (Bu4N)3Os(CN)6 showed a sharp negative line at 4110 cm−1, with some weaker bands to higher energy.