Über die einwirkung metallorganischer verbindungen auf chinole. VII

Zusammenfassung Es wird gezeigt, daß für die Einwirkung von metallorganischen Verbindungen auf o- und p-Chinolacetate neben dem früher allein diskutierten Reaktionsverlauf entsprechend dem Schema II (S. 33/34) das Schema III (S. 35/36) vorwiegend zu berücksichtigen ist. Im letzteren spielt die bisher nicht beobachtete Reaktion 2, die im Schema II überhaupt keine Berücksichtigung gefunden hat, eine bedeutende Rolle. Die Art der erhaltenen Reaktionsprodukte läßt sich qualitativ durch Berücksichtigung von Geschwindigkeitsunterschieden der verschiedenen, in Betracht kommenden Reaktionen der Schemata II und III erklären. Diese Überlegungen werden gestützt durch Versuche an acylierten Acyloinen, für welche in einem von der Konstitution abhängigen Ausmaß die Reaktion 2 (vgl. Schema I, S. 28) von Bedeutung ist.Auszugsweise vorgetragen (F. W.) am XIV. Intern. Kongress f. reine und angew. Chemie, Zürich, Juli 1955. VI. Mitt.: Mh. Chem.86, 912 (1955). V. Mitt.: Mh. Chem.86, 831 (1955). Diese Arbeit wurde irrtümlich als IV. Mitt. bezeichnet.Herrn Prof. Dr.A. Wacek zum 60. Geburtstag in alter Freundschaft gewidmet (F. W.).     

Effect of headgroup size on permeability of Newton black films

Gas permeability and thin-film interferometry are used as a tool to elucidate the orientation of polymeric headgroups in free-standing foam films. Nonionic polyoxyethylene (EO) surfactants were used to stabilize the foam films, keeping the size of the hydrophobic part constant (C12) and varying the size of the hydrophilic (EO numbers) part. The effect of headgroup size on the gas permeability of Newton black foam films was studied. Thickness, contact angle, and surface tension were measured to understand the permeation mechanism. Increase of film thickness and surface tension was observed while increasing the headgroup size, but the contact angle remains small and constant. Upon increasing the headgroup size, the permeability decreases showing that the headgroups provide a resistance to permeation. For smaller headgroups, the permeability follows a linear dependence on the film thickness, whereas for larger headgroups, the permeability essentially deviates from linearity. We use the conventional "coil model" of the EO chains to explain the observed results providing a detailed picture of the orientation of this important molecule in a confined volume of foam films.     

Dramatic variation of magnetic exchange through double end-on azide bridges in a series of ladder-like copper(II) coordination polymers

Three ladder-like coordination polymers, [Cu2(phprpy)2-mu-(N3)2(N3)2], 1; [Cu2(terpy)2-mu-(N3)4Cu2-mu-(N3)2(N3)2], 2; and[Cu2(terpy)2-mu-(N3)2(N3)2Cu3-mu-(N3)4(N3)2], 3, consisting of Cu2+ ions with double end-on azide bridges were synthesized, their crystal structures and magnetic properties were determined, and spin dimer analysis was performed to explain the signs and strengths of their strong spin exchange interactions [phprpy is 4-(3-phenylpropyl)pyridine and terpy is 2,2':6,2'-terpyridine]. Although these compounds have ladder-like arrangements of Cu2+ ions, their magnetic structures are described as isolated dimers for 1 and 2 and as isolated trimers for 3. The predominant spin exchange paths in 1-3 have double end-on azide bridges linking adjacent Cu2+ ions, and the geometrical parameters of these bridging structures are similar. However, the spin dimer of 1 exhibits a strong ferromagnetic coupling; that of 2, a strong antiferromagnetic coupling; and that of 3, a weak ferromagnetic coupling. These findings are well explained by the present spin dimer analysis and show that the nature and geometry of the nonbridging ligands can have a strong influence on the sign and strength of the spin exchange interaction between Cu2+ ions connected by double end-on azide bridges.     

Über die Darstellung von Azidophenolen

Zusammenfassung Es wird gezeigt, daß die o-Chinolacetate, die als Substituenten nur Alkylreste tragen, z. B.1, nicht mit dem Azidion im methanol. oder essigsaurer Lösung reagieren. Mit den o-Chinolacetaten2–5 erfolgt der Eintritt des genannten Ions unter gleichzeitiger Aromatisierung und Bildung der Azidophenole2 a, 3 a, 4 a und5 a.

---

It is shown that o-quinol acetates which bear only alkyl groups as substituents, e. g.1, do not react with the azide ion in methanol or dilute acetic acid solution. In contrast, N ₃ ^– adds to the o-quinol acetates2–5 with simultaneous aromatization forming the azidophenols2 a, 3 a, 4 a and5 a.

---

---

Herrn Prof. DDr. h. c.V. Prelog zum 60. Geburtstag.     

Investigation of the scanning tunneling microscopy image, the stacking pattern, and the bias-voltage-dependent structural instability of 1,10'-phenanthroline molecules adsorbed on Au(111) in terms of electronic structure calculations

A self-assembled monolayer of 1,10'-phenanthroline (phen) molecules on Au(111) was found to undergo a structural phase transition when the bias voltage is switched in scanning tunneling microscopy (STM) experiments (Phys. Rev. Lett. 1995, 75, 2376; Surf. Sci. 1997, 389, 19). The nature of two bright spots representing each phen molecule in the high-resolution STM images of phen molecules on Au(111) was identified by calculating the partial density plots for a monolayer of phen molecules adsorbed on Au(111) with tight-binding electronic structure calculations. The stacking pattern of chains of phen molecules on Au(111) was explained by studying the intermolecular interactions between phen molecules on the basis of first-principles electronic structure calculations for a phen dimer, (phen)(2). The structural instability of phen molecule arrangement caused by the bias-voltage switch was probed by estimating the adsorbate-surface interaction energy with the point-charge approximation for Au(111).     

Buchbesprechungen

Ohne Zusammenfassung     

Über die Einwirkung von metallorganischen Verbindungen auf Chinole II

Zusammenfassung Bei der Einwirkung von CH₃MgX, CH₃Li, C₆H₅MgBr und C₆H₅Li auf das Diacetat des 4-Methyl-2-oxy-o-chinols I entstehen in der Hauptmenge disubstituierte Brenzkatechine vom Typus II. Ihre Bildung erklärt sich durch eine 1,4-Addition der metallorganischen Verbindung an das konjugierte System von I. Zum Unterschied von den genannten metallorganischen Verbindungen liefert C₂H₅MgBr als Hauptreaktionsprodukt 3-Oxy-4-äthoxy-toluol. Die bisher beiGrignard-Reaktionen nicht beobachtete Bildung eines Äthers wird durch eine primäre 1,2-Addition derGrignard-Verbindungen I erklärt, der nachträglich eine Umlagerung unter Bildung des aromatischen Äthers folgt.     

Über die Reduktion cyclischer Acylale mit LiAlH4

Zusammenfassung Reduktion der cyclischen Acylale1 (a bzw.b) mit LiAlH₄ führt zu den erwarteten Diolen5 (a bzw.b). Bei2 hingegen wird lediglich die olefinische Doppelbindung reduziert, was durch die Ausbildung eines gegen weiteren H^–-Angriff stabilisierten, mesomeren Anions zu erklären ist. Auch die Verbindung4 ist gegen LiAlH₄ stabil.

---

Reduction of the cyclic acylals1 (a andb) with LiAlH₄ yields the expected diols5 (a andb). In contrast, only the olefinic double bond of2 is reduced, owing to the formation of a mesomeric anion which resists further attack by hydride ion. The compound4 is also stable to LiAlH₄.

     

From homoleptic to heteroleptic double stranded Copper(I) helicates: the role of self-recognition in self-assembly processes

The ligands 2,9-bis[(6-methyl-2, 2'-bipyridin-6'-yl)methyleneoxymethylenyl]-1,10-phenanthroline (6), 6' ',6' "-bis[(6-methyl-2, 2'-bipyridin-6'-yl)methyleneoxymethylenyl)]-2' ',2' "-bipyridine (2), 5,5'-bis[(6-methyl-2,2'-bipyridin-6'yl)methyleneoxymethylenyl]-2, 2'-bithiophene (7), and 6,6'-bis[(6-methyl-2, 2'-bipyridin-6'-yl)methyleneoxymethylenyl]-2,2'-biphenyl (8) and their respective homo- and heteroleptic double-stranded copper(I) complexes were prepared and characterized in order to estimate the importance of self-recognition in the self-assembly processes of double-stranded copper complexes. The homoleptic double-stranded copper complexes of 2, 6, 7, and 8 were characterized by NMR, FAB-MS, and electrochemistry. It was found that 6 and 2 each form a single double-stranded helicate having the structure of [(L)(2)Cu(3)](3+) (L = 2 or 6), 7 forms two double-stranded [(7)(2)Cu(3)](3+) complexes, and 8 results in a mixture of at least two [(8)(2)Cu(2)](2+) complexes. The potential shift, DeltaE degrees (,) of the Cu(+)/Cu(2+) redox process of these complexes reflects the binding affinity of the different binding sites to the copper cation. The electrochemical data show that the central units have a higher affinity to Cu(+) as compared to the off-center binding sites. NMR was used to determine the actual complex composition obtained from different mixtures of 2, 6, or 7 with Cu(+). Interestingly, we have found that, although 6, 2, and 7 each form homoleptic double-stranded complexes, no heteroleptic double-stranded copper complexes were formed from the mixtures of 7 with either 6 or 2. However, when mixtures of 6 and 2 are used, helicate distributions seem to follow simple statistics. These results are discussed in terms of the relative importance of self-recognition in the self-assembly of double-stranded helicates.