Mass spectrometry of onium compounds—IX: On the evaporation of anilinium oxides. Ionization potential measurements

o-N,N,N-Trimethylanilinium oxide is evaporated structurally unchanged, admixed with the corresponding transalkylated ether. The ionization potential for the anilinium oxide was determined as 6·8 eV which was 0·8 eV lower than for the corresponding ether. An explanation for the unusually low IP value is advanced. In IP measurements in binary mixtures the semi-log plot method showed parallel curves for different compositions in the gas phase, but no linear relationship between the recorded IP and composition was found. Appearance potential measurements show that the energy of the zwitterion in the gas phase is at least 10 kcal/mol higher than in the corresponding ether.     

Mass spectrometry of onium compounds—X: on the evaporation of pyridinium-3-oxides ionization potential measurements

Ionization potentials of a number of substituted pyridines have been measured. The ionization potential is dependent on the substituent properties. Derivatives of pyridinium-3-oxide are unusual in that they have considerably lower IP values than isomeric covalent structures.     

Design, synthesis and characterization of a Pt-Gd metal-organic framework containing potentially catalytically active sites

The heterobimetallic metal-organic framework {[(BPDC)PtCl(2)](3)(Gd(H(2)O)(3))(2)}.5H(2)O (BPDC = 2,2'-bipyridine-5,5'-dicarboxylate) has been designed and synthesized by hydrothermal methods. The new coordination polymer contains subunits of (BPDC)PtCl(2) (1) where both N atoms of the BPDC ligand are attached to a square-planar Pt(II) center. The two remaining cis coordination sites at Pt(II) are occupied by chloride ions. The final structure (2) of the polymeric network is obtained when Gd(III) ions link together the (BPDC)PtCl(2) units, which are organized in sheets, into larger blocks. These blocks are stacked along the crystallographic [010] direction and are held together by a hydrogen bonding scheme that involves carboxylate oxygen atoms and water molecules in the coordination sphere of Gd. The coordination polymer 2 can be obtained in a single-step reaction or in a two-step synthesis where the corresponding Pt complex (1) was first synthesized followed by reacting 1 with Gd(NO(3))(3).6H(2)O. In situ high temperature powder X-ray diffraction shows that the crystalline coordination polymer transforms into an anhydrous modification at 100 degrees C. This modification is stable to 350 degrees C, at which temperature the structure starts to decompose. The coordination sphere around platinum in the polymer closely resembles organometallic Pt complexes that have been previously found to catalytically or stoichiometrically activate and functionalize hydrocarbon C-H bonds in homogeneous systems.     

Syntheses,structures and magnetic properties of Mn(II) containing 3D polymeric networks

Two novel 3D coordination polymers {[Mn(aip)(DMF)]}_n, CPO-9, and {[Mn₃(Hatp)₂(atp)₂](H₂O)₂(DEF)₄}_n CPO-10 (aip = 5-aminoisophthalate, atp = 2-aminoterephthalate, DMF = dimethylformamide, DEF = diethylformamide) have been synthesized by solvothermal methods. Their properties have been studied by single-crystal X-ray diffraction, thermogravimetric analysis, high-temperature powder X-ray diffraction and magnetic susceptibility measurements. The crystal structure of CPO-9 is based on infinite chains of carboxylato-bridged five-coordinated Mn(II) ions that are crosslinked via the aip ligands to form a 3D structure. CPO-10 is based on linear trinuclear building units of carboxylato-bridged octahedral Mn(II) ions that are crosslinked by the atp ligands into a 3D structure. Both compounds have 1D channels that contain solvent molecules. The solvent accessible void volume for CPO-10 is 51.9% of the unit cell volume. For both compounds, however, the solvent molecules cannot be removed without the collapse of the structures into amorphous phases at 250 °C. The magnetic susceptibility measurements indicate antiferromagnetic couplings between the Mn(II) ions in both compounds. The magnetic data have been fitted using theoretical approaches.     

Drag amplification of long flexible riser models undergoing multi-mode VIV in uniform currents

Measurement data of long flexible riser models are used to study the drag amplification due to multi-mode vortex induced vibration (VIV). The riser model was towed in a towing tank, and vibration along its length was measured indirectly at a set of discrete points using accelerometers, along with the total drag and lift forces on the model. These data were used to fit expressions for the drag amplification taking into account the spatial variation of the vibration amplitude along the riser length. The results were compared with the existing empirical expression used in the VIV analysis tool SHEAR7 as well as other test data. It was found that the expression in SHEAR7 agrees well with the test data. However, for larger vibration amplitudes, it appears to under-predict the drag amplification.     

Photochemistry of the anthracene chromophore: Triplet-sensitized isomerizations of dianthrylethanes

The photochemical isomerization of 1,2-di(9-anthryl)ethane can be sensitized by biacetyl to proceed by intramolecular Diels-Alder reaction. The molecular geometry of dianthrylethanes affects their triplet state reactivity.     

Separation of the isochromatics-isopachics patterns by use of retarders in holographic photoelasticity

By double passing the object beam in photoelastic-holographic interferometry, separation of the isochromatic-isopachic patterns can be achieved. The object beam must then interact with a suitable polarizing element between the first and second pass. This problem is analyzed using Jones' matrices. This analysis shows that, apart from active and passive rotators, half-wave and quarter-wave retarders can also be used as polarizing elements. Possible experimental arrangements of the method are reviewed and experimental verifications are presented.     

API stepsize control for the numerical solution of ordinary differential equations

A control-theoretic approach is used to design a new automatic stepsize control algorithm for the numerical integration of ODE's. The new control algorithm is more robust at little extra expense. Its improved performance is particularly evident when the stepsize is limited by numerical stability. Comparative numerical tests are presented.     

A reinvestigation of the thermal rearrangements of naphthvalene

The previously reported thermal transformation of naphthvalene to benzofulvene has been shown to be a catalyzed process; naphthvalene rearranges to naphthalene under flow pyrolysis conditions.