Beiträge zur Chemie der Pyrrolpigmente, 38. Mitt.: Zur Assoziation von Gallenpigmenten

The long standing problem of solvent dependent absorption spectra of certain bile pigments such as bilirubindimethylester has been solved by measurement of molecular masses by means of vapour pressure osmometry. Using this method and the investigation of the concentration and temperature dependence of the absorption spectra on several model compounds an association equilibrium for pigments of the rubinoid structural type could be confirmed. Moreover the optical properties of the coexisting species and the corresponding equilibrium constants could be deduced by spectroscopic techniques. Verdinoid pigments lacking free carboxylic functions on the other hand tend to be monomeric in solution. A heteroassociated species involving equimolar amounts of a verdinoid and a rubinoid pigment could be verified existing on adsorbents like silicagel.

37. Mitt.:Falk, H., Thirring, K., Tetrahedron, im Druck.     

Chemistry of polyfunctional molecules-123. Reactions of BiBr3, SbI3 and AsI3 with LiN(PPh2)2; X-ray structure of a cyclophosphazene salt containing arsenic(I)

BiBr₃ or SbI₃ react at 20°C with LiN(PPh₂)₂ (1) to give elementary Bi or Sb and the P---P coupled phosphazene ligand Ph₂P---N=PPh₂---PPh₂=N---PPh₂ (2). The reaction of AsI₃ with 1 at room temperature formed yellow needles of the eight-membered heterocycle (3), whereas AsI₃ interacted at 80°C with 1 in the molar ratio of 1:3 to give elementary arsenic and 2. Treatment of AsI₃ and 1 at 20°C in a 1:2 stoichiometry yielded the seven-membered, cyclic arsenium(I) salt

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I·4THF (5·4THF), which was characterized by elemental analysis, conductivity, mass, IR and NMR spectroscopy and single-crystal X-ray structural analysis.     

Beiträge zur Chemie der Pyrrolpigmente, 70. Mitt.: Zum aktiven Transport mit tripyrrinoiden Liganden

The tripyrrin carboxylic acid6 exhibits a pronounced efficiency for carrier mediated proton driven secondary active transport (counter transport) for a series of toxic or valuable cations in a bulk chloroform membrane. In case of Zn⁺⁺ ions the mechanism including complete concentration profiles forNerst diffusion layers and bulk phase have been established. This compound might be used for detoxification or enrichment of precious metals using membrane separation systems.

Herrn Prof. Dr.A. Neckel mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Ferrocenasymmetrie, 5. Mitt.: Die Anwendung eines halbempirischen Rechenverfahrens auf optisch aktive Ferrocenderivate

The procedure ofBrewster was employed in the calculation of the molecular rotation of optically active derivatives of 1,2-tetramethylene-ferrocene, which (in addition to ferrocene asymmetry) contain asymmetric (chiral) centers in the cyclohexene part of the molecule. Satisfactory agreement between the calculated and observed values for the rotations was obtained throughout. In one case, the calculation of the absolute configuration of the planarasymmetric part was successful; it was found to be in agreement with the results of an independent (experimental) method employed earlier. The absolute conformation of some of the ferrocene derivatives is discussed with the aid of optical circular dichroism.     

Zur Chemie der Pyrrolpigmente, 56. Mitt.

From an investigation of the ICD of bilatrienes-abc and 2,3-dihydrobilatrienes-abc induced by mixtures of CCl₄ with (+)-cis-Pinane, (–)-lactic and (+)-tartaric acid esters it is concluded that specific interactions between chromophore and the chiral reagents afford a partial resolution of the labile racemate of helices. Attaching chiral residues covalently to the chromophore induces very low resolution of the same kind in case of apolar ligands like a cholesteryl-residue. However, with polar ligands as in the case ofBoc-lysyl derivatives enantiomeric excesses up to 90% are achieved depending on the solvent used.

Herrn Prof. Dr.Karl Schlögl zu seinem 60. Geburtstag gewidmet.     

Beiträge zur Chemie der Pyrrolpigmente, 9. Mitt.: Bildung,Struktur und Konfiguration vonZ- undE-Arylmethyliden-3,4-dimethyl-3-pyrrolin-2-onen

The condensation of 3.4-dimethyl-3-pyrrolin-2-one with p-methyl-, p-chloro-benzaldehyde and ferrocenealdehyde yields theZ-andE-isomers of the corresponding condensates. Due to kinetic control theZ-isomers are obtained almost exclusively in this reaction. TheE-isomers of the two firstmentioned products can be produced by photochemical isomerization. The structures (tautomeric forms) and configurations of the isomers were established by the Lanthanide-induced-shift-technique and by evaluating the Nuclear-Overhauser-Effect.