Studies of the atom-dimer polarization transfer

The polarization transfer between optically pumped alkali atoms and alkali molecules is studied, using the model introduced in a previous paper (Z. Physik A273, 9(1975)). It is shown that the atom-molecule-exchange reactionX+X ₂→X ₂+X is responsible for the nulear spin polarization observed in the alkali molecules, and that the recombination of the alkali atoms does not contribute to this polarization transfer.     

Analysis of green copper pigments in illuminated manuscripts by micro-Raman spectroscopy

In the majority of the literature describing green coloured materials used on ancient painting layers (15th or 16th century), two copper greens are mainly cited: malachite [CuCOr3 x Cu(OH)2] and verdigris [Cu(CH3COO)2 x [Cu(OH)2]3 x 2H2O]. It is shown, by micro-Raman spectroscopy, that the artists were actually employing more than these two copper greens, in particular various copper sulfates, among which the most common pigment found is posnjakite [CuSO4 x 3Cu(OH)2 x H2O]. In contrast to the PIXE (particle induced X-ray emission) technique, Raman spectroscopy is a technique of choice, able to distinguish not only a copper sulfate from a carbonate or acetate but also the different sulfates themselves; in this respect, we found that the high wavenumber region (2800-4000 cm(-1)), characteristic of H2O vibrations, is of particular interest. It is also shown that numerous green areas were created with mixtures of a copper sulfate mixed with other pigments, for instance to enhance the colour depth. Finally, in some cases, no green pigment is actually employed but the colour is obtained by intimately mixing yellow and blue pigments. All these results led to a new look at the pigments which were in use on the palettes of the ancient artists.     

The infrared spectrum of Au-.CO2

The Au-.CO2 ion-molecule complex has been studied by gas phase infrared photodissociation spectroscopy. Several sharp transitions can be identified as combination bands involving the asymmetric stretch vibrational mode of the CO2 ligand. Their frequencies are redshifted by several hundred cm(-1) from the frequencies of free CO2. We discuss our findings in the framework of ab initio and density-functional theory calculations, using anharmonic corrections to predict vibrational transition energies. The infrared spectrum is consistent with the formation of an aurylcarboxylate anion with a strongly bent CO2 subunit.     

SynCar: an approach to automated synthesis

The automation of all aspects of manual solution-phase synthesis into one integrated, efficient, and reliable system could be regarded as something of an unmet challenge in organic chemistry. The requirements for modern solution-phase libraries in mainstream drug discovery is typically 50-250 high-purity compounds on a 10-100-mg scale, whether for target class libraries or lead optimization, and short cycle time in combination with high capacity is critical. To achieve these goals, in a codevelopment between Aventis and Accelab GmbH, Kusterdingen, Germany, we designed a completely novel system of independent workstations connected by a shuttle transfer system produced by Montech, Derendingen, Switzerland. Seven modular workstations process four reactions on each shuttle in parallel, with the ability to perform synthesis (temperature control and liquid reagent handling), filtration, liquid-liquid extraction, evaporation, weighing, solid-phase extraction, and HPLC/MS analysis. The modular design enables the continuous loading of shuttles at any time, and each shuttle can have its own workflow. The design also allows easy expansion for future needs. The result is a combination of high flexibility and high throughput.     

Neue Kupferkomplexe mit Phosphaalkenliganden. Molekülstruktur von [Cu{P(Mes*)C(NMe2)2}2]BF4 (Mes* = 2,4,6‐tBu3C6H2)

New Copper Complexes Containing Phosphaalkene Ligands. Molecular Structure of [Cu{P(Mes*)C(NMe₂)₂}₂]BF₄ (Mes* = 2,4,6‐tBu₃C₆H₂) Reaction of equimolar amounts of the inversely polarized phosphaalkene tBuP=C(NMe₂)₂ ( 1a ) and copper(I) bromide or copper(I) iodide, respectively, affords complexes [Cu₃X₃{μ‐P(tBu)C(NMe₂)₂}₃] ( 2 ) (X =Br) and ( 3 ) (X = I) as the formal result of the cyclotrimerization of a 1:1‐adduct. Treatment of 1a with [Cu(L)Cl] (L = PiPr₃; SbiPr₃) leads to the formation of compounds [CuCl(L){P(tBu)C(NMe₂)₂}] ( 4a ) (L = PiPr₃) and ( 4b ) (L = SbiPr₃), respectively. Reaction of [(MeCN)₄Cu]BF₄ with two equivalents of PhP=C(NMe₂)₂ ( 1b ) yields complex [Cu{P(Ph)C(NMe₂)₂}₂]BF₄ ( 5b ). Similarly, compounds [Cu{P(Aryl)C(NMe₂)₂}₂]BF₄ ( 5c (Aryl = Mes and 5d (Aryl = Mes*)) are obtained from ArylP=C(NMe₂)₂ ( 1c : Aryl = Mes; 1d : Mes*) and [(MeCN)₄Cu]BF₄ in the presence of SbiPr₃. Complexes 2 , 3 , 4a , 4b , and 5b‐5d are characterized by means of elemental analyses and spectroscopy (¹H‐, ¹³C{¹H}‐, ³¹P{¹H}‐NMR). The molecular structure of 5d is determined by X‐ray diffraction analysis.     

On the interactive solution to a multicriteria scheduling problem

Summary A mixed integer multiple criteria model is formulated for scheduling problems. Its solution is obtained by an interactive method based on the Tchebycheff-approximation. For solving greater problems some modifications are discussed at the end of the paper, which are essentially based on the notion of heuristic efficiency.

---

Zusammenfassung Da bei Ablaufplanungsproblemen häufig mehrere Zielsetzungen zu beachten sind, wird im folgenden Beitrag hierzu ein gemischt-ganzzahliges multikriterielles Entscheidungsmodell formuliert. Seine Lösung erfolgt mit Hilfe eines interaktiven Verfahrens. Zur numerischen Lösung größerer Problemstellungen sind einzelne Verfahrensmodifikationen erforderlich, die im wesentlichen auf dem im letzten Abschnitt eingeführten Begriff der heuristischen Effizienz aufbauen.

     

Complex forming and extraction properties of oligo benzo-fused crown ethers

The complex forming properties with alkali metal and ammonium ions of a series of oligo benzo-condensed 18-crown-6 ethers1–8 having a different gradation of lipophilicity and of molecular rigidity are investigated by voltammetry at the interface of two immiscible electrolyte solutions (ITIES) and by a liquid-liquid extraction technique. The experimental results obtained in the two phase system H₂O/nitrobenzene are discussed in relation to the structure of the crown and the cation type. The stability constants for the 1 : 1 complexes of Na⁺, K⁺, Rb⁺, Cs⁺ and NH ₄ ⁺ in nitrobenzene have been determined and compared with the extraction constants for the 1: 1 complexes of Na⁺ and K⁺ and for the 1 : 1 and 1 : 2 complexes of Cs⁺, showing the effect of oligo benzo condensation for the 18-crown-6 system.     

Ersatz der Podbielniak-Destillation durch eine Kombination von Graschromatographie und Gravimetrie

Zusammenfassung An Stelle der Podbielniak-Analyse für Gasproben, die neben Inertgasen und leichten Kohlenwasserstoffen auch C₅- und höhere Kohlenwasserstoffe enthalten, wird ein neues Verfahren vorgeschlagen. Die Inertgase und leichten Kohlenwasserstoffe werden wie üblich gaschromatographisch bestimmt. Zusätzlich trennt man aus einer zweiten Probe gaschromatographisch die leichten Anteile ab, spült durch Umkehr der Trägergasrichtung die Summe der schweren Kohlenwasserstoffe wieder aus der Säule und bestimmt ihre Menge durch Wägung.     

Übergangsmetall-substituierte Acylphosphane und Phosphaalkene. 17 [1] Synthese und Struktur der μ-Isophosphaalkin-Komplexe [(η5-C5H5)2(CO)2Fe2(μ-CO)(μ-CPC6H2R3-2,4,6)] (R = Me,iPr, tBu)

Transition Metal Substituted Acylphosphanes and Phosphaalkenes. 17. Synthesis and Structure of the μ-Isophosphaalkyne Complexes [(η⁵-C₅H₅)₂(CO)₂Fe₂(μ-CO)(μ-C?PC₆H₂R₃)] (R = Me, iPr, tBu) . Condensation of (η⁵-C₅H₅)₂(CO)₂Fe₂(μ-CO)(μ-CSMe)}⁺SO₃CF₃^? ( 6 ) with 2,4,6-R₃C₆H₂PH(SiMe₃) ( 7 ) ( a : R = Me, b : R = iPr, c : R = tBu) affords the complexes (η⁵-C₅H₅)₂(CO)₂Fe₂(μ-CO)(η-C?PC₆H₂R₃-2,4,6) ( 9 a–c ) with edge-bridging isophosphaalkyne ligands as confirmed by the x-ray structure analysis of 9 a .     

A photoactivated diazopyruvoyl cross-linking agent for bonding tissue containing type-I collagen

On the basis of the earlier examples of diazopyruvoyl (DAP) groups reported by Lawton for covalent binding and cross-linking of proteins and oligopeptides and our recent demonstration that a coumaryl diazopyruvamide was used to label Type-I collagen, we have extended our investigations to the synthesis and cross-linking capabilities of a bis-DAP polyethylene glycol to cross-link Type-I collagen. The new photoactivated cross-linking agent, N,N'-bis(3-diazopyruvoyl)-2,2'-(ethylenedioxy)bis(ethylamine) (DPD, 2), has been designed and synthesized specifically to "weld" collagenous tissues by cross-linking Type-I collagen. A working model for the photochemical welding studies of collagenous tissues was developed using gelatin strips (gel strips) composed of denatured Type-I collagen. Gel strips are transparent to near-UV and visible light, uniform in thickness, and have reproducible composition. Furthermore, the availability of nucleophilic amine sites in gel strips was demonstrated by reaction with o-phthalaldehyde, producing a fluorescent derivative of the protein. Gel strips were coated with a solution of DPD in chloroform 7 irradiated at 320-390 nm, and the resulting bonded gel strips were tested for the strength of the weld. The welds were generally brittle and had average tensile strengths that exceeded 100 N/cm2. Welds were not formed in the absence of light or DPD. Scanning electron microscopy studies revealed a pockmarked surface from severed welds. Welds of rabbit Achilles tendon were also obtained using the tethered diazopyruvamide. These welds were much weaker, having an average tensile strength of 11.95 N/cm2 for DPD-2,2'-ethylenedioxy(bis)ethylamine comonomers in the cross-linking reaction. In both studies the welds obtained by this method were significantly stronger than the controls.