Textural and calorimetric investigations on a homologous series of mesogenic azocompounds complexed with palladium(II)

A comparative study of some mesogenic azobenzene compounds and their organometallic palladium(II) derivatives is reported. On the basis of the textural properties, calorimetric data and uniaxial order parameters (as deduced approximately from infrared spectroscopy), the main features induced by palladium complexation are (i) the transition temperatures increase, (ii) the number of ordered mesophases increases, (iii) the nematic uniaxial order parameter decreases, (iv) the textures are typical of highly ordered phases, and (v) an optical biaxiality appears in the nematic phase. The calorimetric data as well as the order parameters, if discussed in terms of molecular biaxiality result are interpreted at least qualitatively. Optical investigations show that macroscopical biaxial ordering can be achieved.     

Sensitive determination of 3-methoxy-4-hydroxyphenylglycol (MHPG) in human plasma by HPLC with electrochemical detection

Summary This study deals with the development of a new HPLC method for the determination of 3-methoxy-4-hydroxyphenylglycol (MHPG), the main noradrenaline metabolite in human plasma. A Varian reversed-phase column (C₈; 250 mm×4.6 mm i.d.; 5 μm particles) was used as the stationary phase and an aqueous solution of citric acid, 1-octanesulfonic acid, EDTA, and methanol was used as the mobile phase. Coulometric electrochemical detection (ED) was used to obtain the highest sensitivity. Isolation of MHPG from plasma was accomplished by means of a new solid-phase extraction procedure after a protein precipitation step. The extraction yield of MHPG from plasma was very high (>97%). Linearity was observed in the 0.5–25 ng mL⁻¹ concentration range; the limit of detection was 0.2 ng mL⁻¹ and the limit of quantitation was 0.5 ng mL⁻¹. Repeatability (RSD,%) for plasma samples was found to be <3.2% and intermediate precision was <4.3%. The method was applied to the determination of MHPG in the plasma of healthy subjects under experimentally-induced psychological stress.     

Thermotropic mesomorphism in penta- and hepta-coordinated metal complexes

New Ni(II) and UO₂(II) metallomesogens obtained from mesomorphic N,N'-salicyliden(3,3'-diamine-N-methyldipropylamine) ligands containing a pentadentate N₃O₂ chelating cavity and bearing two or four lateral substituents, are isolated and fully characterized. Some of the synthesized nickel and dioxouranium complexes show a SmC mesophase. To the best of our knowledge, these species are the first pentacoordinated Ni(II) and heptacoordinated UO₂(II) metallomesogens to be reported.     

Synthesis and solid state characterization of hexacoordinated 1:1 ionic gallium(III) complexes

The coordination of the N,N ligands 2,2-bipyridine (bipy) and 1,10-phenanthroline (phen) to Ga(III) has been investigated via the formation of new ionic hexacoordinated complexes of general formula [Q'(2)Ga(N,N)][X], where HQ' stands for 2-methyl-8-hydroxyquinoline and the counter anion X(-) is nitrate (NO(3)(-)) or hexafluorophosphate (PF(6)(-)). All synthesized complexes were characterized by single-crystal X-ray diffraction analysis. The geometry of the Ga(III) cations is octahedral and a single geometric isomer (all N, N trans conformation) has been obtained in all cases. The role of both the N,N ligand and the counter anion has been investigated in the formation of the crystal supramolecular motifs occurring in the 3D-crystal networks of these new class of ionic Ga(III) derivatives. A full investigation of the photophysical properties of the new synthesized ionic species is reported and discussed in relation to their crystalline packing and the degree of crystallinity of thin solid films as well as the nature of the N,N ligand and the counter anion.     

Mixed 2-phenylpyridine and 5-substitued-8-hydroxyquinolines palladium(II) complexes: new emitters in solutions at room temperature

The newly synthesized complexes formed by cyclopalladated 2-phenylpyridine co-ordinated to 5-substituted-8-hydroxyquinolines, are at room temperature and in fluid solution, luminescent with an absolute photoluminescent quantum yield which depends on the nature of the substituent in position 5.     

Comparison of different techniques for the FLUENT$^{\copyright}$-based treatment of the electromagnetic field in inductively coupled plasma torches

A new technique for using the CFD commercial code FLUENT ^©^{\copyright} to simulate inductively coupled plasma torches by means of two-dimensional axisymmetric models is presented. The method is based on an external user-defined function (UDF) which fully solves the electromagnetic field equations, letting the FLUENT ^©^{\copyright} built-in module calculate only the plasma temperature and velocity fields inside the torch region. In this framework, computations have been carried out for LTE, optica lly thin argon plasmas at atmospheric pressure, using extended grid models with either magnetic dipole or vanishing vector potential boundary conditions for the electromagnetic field. It is shown that our newly developed technique is up to 60% faster on each iteration than that using user-defined scalars (UDS) previously proposed in the literature, as the need of solving flow field equations also outside the plasma zone is eliminated. Calculations are also performed using exact integral boundary conditions for the vector potential, as given by the standard electromagnetic field approach, taking into account the effects of both exciting and induced currents. The corresponding results are compared with the approximate ones obtained by employing extended grid models, showing that for small radial dimensions of the electromagnetic field domain, the magnetic dipole boundary conditions give more realistic solutions than those assuming a vanish ing vector potential.     

The synthesis and structure of bis(acetonitrile)nitrosyl tris(3,5-dimethylpyrazolyl)borato molybdenum hexafluorophosphate

Summary Treatment of [Mo{HB(3,5-Me₂C₃HN₂)₃}(NO)I₂] with one or two moles of AgPF₆ in acetonitrile afforded the paramagnetic (one unpaired electron) complex [Mo{HB(3,5-Me₂C₃NH₂)₃}(NO)(NCMe)₂][PF₆]. The structure of this complex was determined crystallographically, and the six-coordinate geometry of the complex cation confirmed.