Field-deployed underwater mass spectrometers for investigations of transient chemical systems

The mass spectrometer developments and underwater deployments described in this work are directed toward observations of important reactive and influential inorganic and organic chemicals. Mass spectrometer systems for measurement of dissolved gases and volatile hydrocarbons were created by coupling a membrane analyte-introduction system with linear quadrupole and ion trap mass analyzers. For molecular masses up to 100 amu, the in situ quadrupole system has detection limits on the order of 1-5 ppb. For masses up to approximately 300 amu, the underwater ion trap system detects many volatile hydrocarbons at concentrations below 1 ppb. Both instruments can function autonomously or via interactive communications from a remote control site. Continuous operations can be sustained for up to approximately 12 days. Deployments have initially involved shallow water proof-of-concept operations at depths less than 30 m. Future modifications are planned that will allow operational depths to 200 m.     

Pyridazines. XXXV. Preparation of some novel pyrimido[4,5-c]pyridazine derivatives from 3-alkylamino- and 3-arylamino-4-pyridazinecarboxamides

Facile syntheses of pyrimido[4,5-c]pyridazine-5,7(6H,8H)diones 4 , pyrimido[4,5-c]pyridazin-5(8H)-ones 7–10 , and dihydropyrimido[4,5-c]pyridazin-5(6H)ones 5,6 starting from 3-chloro-4-pyridazinecarbonitrile 1 via aminocarbonitriles 2 and aminocarboxamides 3 are described. In addition, a convenient access to the new aminopyridazinecarbonitrile 11 from the chloronitrile 1, employing the tetrazolo[1,5-b]pyridazine 12 as the key intermediate, is reported.     

Electron impact ionization mass spectrometry and tandem mass spectrometry of phenylalkylpyridazines

The mass spectrometric fragmentation behaviour of pyridazine and four monosubstituted derivatives containing a pbenylalkyl side-chain (3- and 4-benizylpyridazine, 3- and 4-(2-pbenylethyl)pyridazine) was investigated. In the electron impact ionization mess spectra of the 3-substituted compounds abundant [M – H]⁺ peaks are observed. This allows a clear distinction between 3- and 4-substituted pyridazines, as the spectra of the latter isomers show only very weak [M – H]⁺ signals. The stability of [M – H]⁺ ions derived from 3-alkylpyridazines (deduced from only the very low abundance of further fragment ions) gives strong evidence for a cyclic structure of these ions. One fragmentation pathway typical of the parent pyridazine, the [M - N₂] fragmentation, was not detectable with any of the phenylalkylpyridazines investigated. Instead, loss of HCN, H₃CN⁺ and N²H⁺ was observed. An interesting fragmentation, observed with 3-(2-phenylethyl)pyridazine, is the loss of ⁺CH₃ from the molecular ion and also from the [M – H]⁺ ion.     

Reaktionen an komplexgebundenen liganden : XXXIII. Synthese,reaktivität und struktur von eisen-carbonyl-komplexen mit vierzähnigen thioäther-thiolato-liganden

The reaction of the anion [Fe(CO)₂(S₂C₆H₄)₂]^2? with 1,2-C₂H₄Br₂ yields [Fe(CO)₂(dttd)] containing the dianion of the new tetradentate thioether-thiol ligand 2,3,8,9-dibenzo-1,4,7,10-tetrathiadecan (dttd-H₂). Iron(II) salts coordinate CO under normal conditions also in the presence of alkyl mercaptides; the reaction of, e.g., Fe²⁺, 1,2-S₂C₂H₄^2? and CO yields [Fe(CO)₂(S₂C₂H₄)]^2? which reacts with 1,2-C₂H₄Br₂ analogously yielding [Fe(CO)₂(tdd)], (ttd = [1,4,7,10-tetrathiadecane]^2?). As shown by X-ray analysis the iron centre in [Fe(CO)₂(ttd)] is coordinated pseudo-octahedrally by four sulfur atoms and two cis-carbonyl groups. [Fe(CO)₂(dttd)] splits off one CO ligand upon heating in THF yielding [Fe(CO)(dttd)], which on reaction with PMe₃ yields [Fe(CO)(PMe₃)(dttd)]. The new complexes are characterized by elemental analyses as well as by IR, ¹H NMR and mass spectroscopy.     

Pyridazines,LIV: On the synthesis of pyridazine-fused S-heterocycles: Thieno[2,3-c]pyridazine,pyrimido[4′,5′:4,5]thieno[2,3-c]pyridazine,and pyridazino[3,4-b][1,4]benzothiazine

Summary Starting from 3-chloro-4-pyridazinecarbonitrile (1), the thienopyridazine derivatives2 and3 were prepared. Condensation of3 with triethyl orthoformate afforded the novel tricyclic system4. Reaction of1 with 2-aminothiophenol, followed by treatment with NaH/DMSO was found to give the diaza-phenothiazine6 instead of the expected condensed thiazepine.Dedicated with best wishes to Prof. Dr. G. Zigeuner on the occasion of his 70^th anniversary     

Perceiving pitch absolutely: Comparing absolute and relative pitch possessors in a pitch memory task

Background  

The perceptual-cognitive mechanisms and neural correlates of Absolute Pitch (AP) are not fully understood. The aim of this fMRI study was to examine the neural network underlying AP using a pitch memory experiment and contrasting two groups of musicians with each other, those that have AP and those that do not.     

Die Teilräume eines linearen Koordinatenraumes

Ohne Zusammenfassung     

Topology-Selective Ullmann Coupling on Metal Surfaces by Precursor Design and Adsorbate-Substrate Interaction: Towards the Control over Polymer versus Macrocycle Formation

In polymerization reactions, controlling the formation of open-chain versus cyclic product topologies is necessary because of the different properties of polymer chains and macrocycles. Here, we report a topology-selective Ullmann coupling on metal surfaces with control of the ring/chain competition. The precursor employed is 4,4′′-dibromo-ortho-terphenyl (DBOTP), which features a 60° bent feature and polymerizes into zigzag polyphenylene chains on both Au(111) and Ag(111) surface via Ullmann coupling. However, the cyclotrimerization of the precursor occurs only on Ag(111) but not Au(111). It is proposed that the cyclotrimerization reaction on Au(111) is blocked, because the necessary C−C coupling of two carbon radicals with different vertical heights is unfavored. Such height difference stems from the intrinsic steric repulsion between the two ortho-substituted phenyl groups. On Ag(111), the stronger adsorbate-substrate interaction reduces the extent of the tilting of the phenyl group, resulting in a smaller height difference of the carbon radicals and consequently in the increased probability for the formation of the cyclic trimer.     

Direct synthesis of a metalloporphyrin complex on a surface

We demonstrate that well-defined monolayers of a metal complex on a surface can be prepared by direct vapor deposition of the metal atoms on monolayers of the ligand. In particular, ordered monolayers of adsorbed tetraphenylporphyrin (2H-TPP) on a silver surface were exposed to cobalt vapors, resulting in the complexation of the metal by the porphyrin. The formation of the metal complexes was monitored by means of X-ray photoelectron spectroscopy (XPS), which reveals that this metalation reaction leads to a chemical equivalence of all four nitrogen atoms. The described in situ metalation provides a convenient way to produce adsorbed monolayers of more reactive (e.g., air- or solvent-sensitive) or thermally unstable metalloporphyrins that are difficult to evaporate or even to obtain as pure compounds at room temperature.     

A planar water tetramer with tetrahedrally coordinated water embedded in a hydrogen bonding network of [Tc4(CO)12-(mu3-OH)4.4H2O

A virtually planar water tetramer in which the water molecules are virtually tetrahedrally coordinated could be realized in the solid in a three-dimensional network of [Tc4(CO)12-(mu3-OH)4.4H2O]. The network could be produced by cocrystallization of the new cubane-like cluster [Tc(CO)3-(mu3-OH)]4 and water as a complementary component. The amphiphilic behavior of cluster and water results in a highly ordered three-dimensional network. The complementary components, the water tetramer and the cubic cluster, independently of one another form two interpenetrating tetragonal lattice networks held together exclusively by hydrogen bonds.