Neutral and ionic aluminum,gallium, and indium compounds carrying two or three terminal ethynyl groups

The syntheses of the ionic compounds [Li(+).2 dioxane (2,6-iPr(2)C(6)H(3)N(SiMe(3))Al(C triplebond CSiMe(3))(3))(-)].0.75 dioxane (1), [(Li(+))(2).(dioxane)(7)](0.5) [2,6-iPr(2)C(6)H(3)N(SiMe(3))Ga(C triplebond CSiMe(3))(3)(-)].1.5 dioxane (2), and [(Li(+))(2).(dioxane)(7)](0.5) [2,6-iPr(2)C(6)H(3)N(SiMe(3))In(C triplebond CSiMe(3))(3)(-)].1.5 dioxane (3) by the reaction of the corresponding organo metal chloride with LiC triplebond CSiMe(3) are reported. The neutral ethynyl compounds Br-Al(C triplebond CtBu)(2).2 THF (4), Cl-Ga(C triplebond CtBu)(2).THF (5), Cl-In(C triplebond CtBu)(2).2 THF (6), Al(C triplebond CtBu)(3).C[N(Me)CMe](2) (7), Ga(C triplebond CtBu)(3).dioxane (8), and In(C triplebond CtBu)(3).NEt(3) (9) have been obtained in good yields from the reaction of AlBr(3), GaCl(3), and InCl(3) with LiC triplebond CtBu in the presence of a Lewis base. Compound 7 is the first heterocyclic carbene substituted ethynyl derivative. Aluminum and gallium compounds with three terminal ethynyl groups Al(C triplebond CPh)(3).NMe(3) (10) and Ga(C triplebond CPh)(3).NMe(3) (11) have been prepared by the reaction of AlH(3).NMe(3) or GaH(3).NMe(3) with three equivalents of phenylethyne. All the above-mentioned compounds have been structurally studied. In compound 1 the lithium ion is coordinated to the three terminal ethynyl groups, whereas in compounds 2 and 3 the lithium is coordinated to the solvent (dioxane). Compound 8 crystallizes as a coordination polymer with dioxane molecules bridging the individual gallium units.     

A comparative study of surfactant adsorption on model surfaces using the quartz crystal microbalance and the ellipsometer

The nature of hexaethylene glycol mono-n-tetradecyl ether (C(14)EO(6)) layers adsorbed onto different model surfaces was systematically investigated by means of QCM-D (quartz crystal microbalance-dissipation) and ellipsometry. The amount of non-ionic surfactant adsorbed is determined both at hydrophilic and hydrophobic surfaces. In particular, the substrates employed were hydrophilic silica, hydrophobized silica (using dimethyldichlorosilane), and hydrophobized gold surfaces (using 10-thiodecane and 16-thiohexadecane). It was shown that the frequency shift obtained from the QCM-D experiments results in an overestimation of the adsorbed mass. This is attributed to two different effects, viz. water that is coupled to the adsorbed layer due to hydration of the polar region of the surfactant and second water that for other reasons is trapped within the adsorbed layer. Furthermore, from the ellipsometry data the adsorbed layer thickness is determined. By combining the thickness information and the dissipation parameter (obtained from the QCM-D experiments), we note that the dissipation parameter is insufficient in describing the viscoelastic character of thin surfactant films.     

A Quantitative Assessment of „Through-space”︁ and „Through-bond”︁ Interactions. Application to Semi-empirical SCF Models

The scheme of ‘through-space’ and ‘through-bond’ interaction of (semi)localized orbitals, originally proposed by Hoffmann, is reexamined in terms of SCF many-electron treatments. It is shown that the two types of interaction can be characterized by examining the corresponding off-diagonal matrix elements of the Hartree-Fock matrices of the localized or the symmetry adapted localized orbitals and of the partially diagonalized Hartree-Fock matrices referring to ‘precanonical orbitals’. The procedure outlined is applied to three practical examples using the semiempirical many-electron treatments SPINDO, MINDO/2 and CNDO/2:

• a A reassessment of ‘through-space’ and ‘through-bond’ interaction in norbornadiene indicates, that the latter type of interaction is also of importance for the orbital based mainly on the antisymmetric combination of the localized x-orbitals. The differences in the predictions derived from the three models are critically examined.
• b The competition between ‘through-space’ and ‘through-bond’ interaction in the series of bicyclic dienes from norbornadiene to bicyclo[4.2.2]-dcca-7,9-diene and in cyclohexa-1,4-diene, i. e. their dependence on the dihedral angle UI is reexamined. It is found that the rationalization for the orbital crossing near ω = 130° deduccd from PE. spectroscopic data can not be as simple as originally suggested and that the relay’ orbitals responsible for ‘through-bond interaction affecting both the symmetric and the antisymmetric combination of the π-orbitals extend over the whole CC-σ-system of the six membered ring.
• c ‘Through-bond’ interaction of the two lone pair orbitals in 1,4-diazabicyclo[2.2.2]octane is found to be large for their symmetric and the antisymmetric linear combination.

The analysis quoted, draws attention to some of the dangers involved in using semiempirical treatments for the interpretation of PE. data in terms of Koopmans′ theorem, without due caution.     

γ‐HIO3 – a Metastable,Centrosymmetric Polymorph of Iodic Acid

From solutions of chromium(III) perchlorate and periodic acid, single crystals of γ‐HIO₃ were obtained and characterized by single‐crystal X‐ray diffraction, Raman spectroscopy and thermal analysis. The compound crystallizes in the orthorhombic crystal system, space group Pbca (a = 563.92, b = 611.10, c = 1507.16 pm). The structure is built up by dimers (HIO₃)₂, which are formed by hydrogen bonds. The crystals are metastable and transform into the stable modification, α‐HIO₃, within a couple of weeks.     

Biosynthesis of δ-Jasmin Lactone ( = (Z)-Dec-7-eno-5-lactone) and (Z,Z)-Dodeca-6,9-dieno-4-lactone in the Yeast Sporobolomyces odorus

(all-Z)-(9,10,12,13,15,16-²H₆)Octadeca-9,12,15-trienoic acid ( = α-linolenic acid; D₆- 4 ) was synthesized to investigate the biochemical formation of linolenic-acid-derived aroma compounds in cultures of the yeast Sporobolomyces odorus, using an established gas chromatographic/mass spectrometric (GC/MS) method. Three compounds were identified as labeled: (Z)-dec-7-eno-5-lactone (δ-jasmin lactone), (Z,Z)-dodeca-6,9-dieno-4-lactone, and (2E,4Z)-hepta-2,4-dienoic acid. Both lactones were biosynthesized mostly under conservation of the initial configuration from their corresponding oxygenated linolenic-acid intermediates. The application of (13S,9Z,11E,15Z)-13-hydroxy(9,10,12,13,15, 16-²H₆)octadeca-9,11,15-trienoic acid (D₆- 7 ) as a OH-functionalized precursor of δ-jasmin lactone allowed to gain insight into the stereochemical course of the biosynthesis to both enantiomers of this lactone. In this experiment, 88.3% of the metabolized labeled precursor was transformed under retention of the original configuration of the (R)-enantiomer. This investigation is also a contribution to a better understanding of the C?C bond isomerization steps which took place during the β-oxidative degradation of the substrate.     

Cathodoluminescence Depth Profiling in SiO2:Ge Layers

 For investigation of the luminescent center profile cathodoluminescence measurements are used under variation of the primary electron energy E ₀ = 2…30 keV. Applying a constant incident power regime (E ₀·I ₀ = const), the depth profiles of luminescent centers are deduced from the range of the electron energy transfer profiles dE/dx. Thermally grown SiO₂ layers of thickness d = 500 nm have been implanted by Ge⁺-ions of energy 350 keV and doses (0.5–5)10¹⁶ ions/cm². Thus Ge profiles with a concentration maximum of (0.4 – 4) at% at the depth of d_m≅240 nm are expected. Afterwards the layers have been partially annealed up to T _a = 1100 °C for one hour in dry nitrogen. After thermal annealing, not only the typical violet luminescence (λ = 400 nm) of the Ge centers is strongly increased but also the luminescent center profiles are shifted from about 250 nm to 170 nm depth towards the surface. This process should be described by Ge diffusion processes, precipitation and finally Ge nanocluster formation. Additionally, a Ge surface layer is piled-up extending to a depth of roughly 25 nm.     

Syntheses of macrocyclic bisbibenzyls on solid support

We describe a route for the polymer supported total synthesis of the cyclic bisbibenzyls of the isoplagiochin type found in liverworts. TentaGel^® resins were used as solid support for a sequence involving Suzuki, Wittig and hydrogenation protocols. The polymer linked intermediates could be characterized by HR-MAS NMR. This route is to be extended to the synthesis of small libraries of differently halogenated derivatives.     

Palladium salicylaldimine complexes containing boronate esters

Reactions of salicylaldehydes with boronate ester derivatives of aniline have been examined. Addition of these Schiff base ligands to palladium acetate or Na₂PdCl₄ afforded novel boron-containing trans-bis(N-arylsalicylaldiminato) palladium complexes.Condensation of salicylaldehyde (2-HOC₆H₄C(O)H) with H₂NC₆H₄Bpin (pin=1,2-O₂C₂Me₄) afforded the boron-containing Schiff bases, 2-HOC₆H₄C(H)=NC₆H₄Bpin (1–3a). Similar reactivity with 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde gave the corresponding Schiff bases (1-3b) and (1-3c), respectively. Reaction of Schiff bases (2) and (3) with palladium acetate or Na₂PdCl₄ afforded complexes of the type PdL₂ (4,5), where L=deprotonated Schiff base. The molecular structure of the nitro-salicylaldehyde 4-Bpin palladium complex (5b) was characterized by an X-ray diffraction study. All new palladium compounds have been characterized fully and tested for their antifungal activity against Aspergillus niger and Aspergillus flavus.