An antiferromagnetically coupled hexanuclear copper(II) Schiff base complex containing phenoxo and dicyanamido bridges: Structural aspects and magnetic properties

A novel hexanuclear complex [{(CuL)₂Cu}₂(μ-dca)₂](ClO₄)₂·2L′(1) (where H₂L = (OH)C₆H₄C(CH₃)N(CH₂)₃NC(CH₃)C₆H₄(OH) or N,N′-bis(2-hydroxyacetophenone) propylenediimine and dca = N(CN)₂⁻ and L′ = 2-hydroxyacetophenone) has been synthesized and characterized by elemental analysis, UV-Vis, FT-IR spectroscopic and electrochemical methods. Single crystal X-ray structural characterization reveals a centrosymmetric nature of the complex unit, where the metal centers adopt distorted square-planar and distorted octahedral geometries. Structural analysis also reveals μ₂-phenoxo bridges between terminal and the central copper(II) centers of the asymmetric [(CuL)₂Cu(dca)] unit, the latter being interconnected to its symmetry related counterpart by double μ_1,5-dca bridges, leading to the hexanuclear complex ion [{(CuL)₂Cu}₂(μ-dca)₂]²⁺. Low temperature susceptibility measurements of 1 revealed the presence of strong antiferromagnetic coupling (2J = −407 cm⁻¹) between the copper(II) centers.     

Adsorptive behavior of CO2, CH4 and their mixtures in carbon nanospace: a molecular simulation study

Using molecular simulation, four types of nanoporous carbons are examined as adsorbents for the separation of CO(2)/CH(4) mixtures at ambient temperature and pressures up to 10 MPa. First, the adsorption selectivity of CO(2) is investigated in carbon slit pores and single-walled carbon nanotube bundles in order to find the optimal pore dimensions for CO(2) separation. Then, the adsorptive properties of the optimized slit pore and nanotube bundle are compared with two realistic nanoporous carbon models: a carbon replica of zeolite Y and an amorphous carbon. For the four carbon models, adsorption isotherms and isosteric heats of adsorption are presented for both pure components and mixtures. Special attention is given to the calculation of excess isotherms and isosteric heats, which are necessary to assess the performance of model nanoporous materials in the context of experimental measurements. From these results, we discuss the impact that variables such as pore size, pore morphology, pressure and mixture composition have on the performance of nanoporous carbons for CO(2) separation.     

A combined experimental inelastic neutron scattering, Raman and ab initio lattice dynamics study of α-lithium amidoborane

A combination of inelastic neutron scattering (INS) spectroscopy and Raman spectroscopy with periodic density functional theory calculations is used to provide a complete assignment of the vibrational spectra of α-lithium amidoborane (α-LiNH(2)BH(3)). The Born charge density and the atomic motion up to the decomposition temperature have been modelled. These models not only explain the nature of bonding in α-LiNH(2)BH(3) but also provide an insight into the atomic mechanisms of its decomposition. The (INS) measurements were performed in the range of 0-4000 cm(-1) on the high-resolution time-of-flight TOSCA INS spectrometer at the ISIS Spallation Neutron Source at the Rutherford Appleton Laboratory.     

Spin crossover in di-, tri- and tetranuclear, mixed-ligand tris(pyrazolyl)methane iron(II) complexes

A series of polynuclear mixed-ligand tris(pyrazolyl)methane iron(II) complexes displaying high temperature spin crossover behaviour has been synthesised. These complexes are of the type [(Fe((3,5-Me(2)pz)(3)CH))(n)(μ-L)](BF(4))(2n), where μ-L is one of five bridging ligands X(CH(2)OCH(2)C(pz)(3))(n), (X = the central linking moiety, pz = pyrazolyl ring and n = 2 (ditopic), 3 (tritopic) or 4 (tetratopic)). Throughout the series the terminal tris(3,5-dimethylpyrazolyl)methane co-ligand (3,5-Me(2)pz)(3)CH and the BF(4)(-) counter anion were kept constant while variations in the central linking moiety have produced three dinuclear complexes and a trinuclear and tetranuclear complex, all isolated as solvates. The three dinuclear complexes are a 1,4-xylene-bridged complex 1·2DME, a 2,6-naphthalene-bridged complex 2·2.5MeCN.2DME and a 1,4-butene-bridged complex 3·2DME. The trinuclear complex 4·solvent (solvent undefined) has a 1,3,5-mesitylene core and the tetranuclear complex, 5·8MeCN.2(t)BuOMe, has a 1,2,4,5-tetramethylbenzene core (DME = dimethoxyethane, (t)BuOMe = tertiarybutyl-methylether). The trinuclear cluster has a "3-up" cup shape with the cups arranging themselves in pairs to form capsules that contain anion guests. All the solvated compounds have been structurally characterised and both the solvated and desolvated versions have had their magnetic and thermal properties thoroughly investigated by variable temperature magnetic susceptibility, differential scanning calorimetric and M?ssbauer spectral methods. They all display typical low spin iron(II) magnetic behaviour at room temperature and all undergo a spin state transition to high spin iron(II) above room temperature. In particular, complex 1·2DME shows an abrupt spin transition which shifts, upon desolvation, to a lower value of T(1/2) and in addition displays a small thermal hysteresis.     

A temperature-dependent order-disorder and crystallographic phase transition in a 0D Fe(II) spin crossover compound and its non-spin crossover Co(II) isomorph

The new dipyridylamino/triazine ligand DDE (N(2),N(2),N(4),N(4)-tetraethyl-N(6),N(6)-di(pyridin-2-yl)-1,3,5-triazine-2,4,6-triamine) has been incorporated into the mononuclear Fe(II) SCO compounds cis-[Fe(II)(NCSe)(2)(DDE)(2)] (1), cis-[Fe(II)(NCBH(3))(2)(DDE)(2)] (2), and cis-[Fe(II)(NCS)(2)(DDE)(2)] (3). Magnetic susceptibility measurements reveal that each of 1, 2 and 3 undergoes a complete, continuous spin transition with a T(?) of ～260 K, ～300 K and ～205 K, respectively. An analogue and isomorph of 1, cis-[Co(II)(NCSe)(2)(DDE)(2)] (4), remains high spin down to low temperatures. Variable temperature single crystal data reveal that 1 and 4 undergo a crystallographic phase transition (from orthorhombic Pbcn at high temperatures to monoclinic P2/c at low temperatures) accompanied by an order-disorder transition of ethyl moieties of the DDE ligand. In the Pbcn phase, the structures of 1 and 4 contain one crystallographically unique M(II) centre, while in the P2/c phase, 1 and 4 contain two crystallographically unique M(II) centres. Variable temperature powder X-ray diffraction experiments reveal that the crystallographic phase transition occurs at ～250 K for 1. The occurrence of the concomitant order-disorder and crystallographic phase transitions undergone by 1 and 4 is not directly apparent in their magnetic susceptibility measurements, and this is likely due to the local environment of the M(II) centres remaining largely undisturbed as the transitions occur. The compound 2 is isostructural to 1 and 4 at low temperatures.     

A first step towards practical single cell proteomics: a microfluidic antibody capture chip with TIRF detection

We have developed a generic platform to undertake the analysis of protein copy number from single cells. The approach described here is 'all-optical' whereby single cells are manipulated into separate analysis chambers using an optical trap; single cells are lysed by a shock wave caused by laser-induced microcavitation, and the protein released from a single cell is measured by total internal reflection microscopy as it is bound to micro-printed antibody spots within the device. The platform was tested using GFP transfected cells and the relative precision of the measurement method was determined to be 88%. Single cell measurements were also made on a breast cancer cell line to measure the relative levels of unlabelled human tumour suppressor protein p53 using a chip incorporating an antibody sandwich assay format. These results suggest that this is a viable method for measuring relative protein levels in single cells.     

Facile formation of Pt and PtPd nanoparticles on reactive carbon-TiO2 nanosheet substrates

A novel nanosheet carbon-TiO(2) support is used as a highly reactive substrate for the facile formation of well-dispersed 3-5 nm Pt and PdPt nanoparticles. The synthetic strategy does not require the use of ligands, strong reducing agent or heat.