Mosaics of combinatorial designs for information-theoretic security

Designs, Codes and Cryptography - We study security functions which can serve to establish semantic security for the two central problems of information-theoretic security: the wiretap channel, and...     

Dynamic Interactions in Synthetic Receptors: A Guest Exchange Saturation Transfer Study

The accumulated knowledge regarding molecular architectures is based on established, reliable, and accessible analytical tools that provide robust structural and functional information on assemblies. However, both the dynamicity and low population of noncovalently interacting moieties within studied molecular systems limit the efficiency and accuracy of traditional methods. Herein, the use of a saturation transfer-based NMR approach to study the dynamic binding characteristics of an anion to a series of synthetic receptors derived from bambusuril macrocycles is demonstrated. The exchange rates of BF₄⁻ are mediated by the side chains on the receptor (100 s⁻¹<k_ex<5000 s⁻¹), which play a critical role in receptor-anion binding dynamics. The signal amplification obtained with this approach allows for the identification of different types of intermolecular interactions between the receptor and the anion, something that could not have been detected by techniques hitherto used to study molecular assemblies. These findings, which are supported by a computational molecular dynamic study, demonstrate the uniqueness and added value of this NMR method.     

Über die Löslichkeit des Berlinerblaus

Ohne ZusammenfassungHerrn Ingenieur E. Hofmann danke ich fÜr seine bewährte UnterstÜtzung.     

Stereochemie von Metallocenen, 40. Mitt.

Starting from optically active methylferrocene-- and--carboxylic acids (1 a and1 b) of known absolute configuration and enantiomeric purity about 15 chiral ferrocenes (of each isomeric series— and ) were obtained by suitable ligand transformations. Thereby (almost) all possible chiral combinations of the ligands CH₃, COOH (COO^–), COOCH₃, CN and NH₂ (NH₃ ⁺) were accessible which are necessary for a potential test of approximations of chirality functions for compounds with basic symmetry C_5v. The chiroptical properties of these disubstituted ferrocenes are recorded.Preliminary tests using a shortened Ansatz revealed large discrepancies between calculated () and found [M]_D-values. Possible reasons for this failure are discussed.

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61. Mitt. über Ferrocenderivate

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39. Mitt.:A. Meyer, H. Neudeck undK. Schlögl, Chem. Ber.110, 1403 (1977).

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60. Mitt.:V. Rapi, K. Schlögl undB. Steinitz, J. Organometal. Chem.94, 87 (1975).     

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Ohne Zusammenfassung     

The magnetic hyperfine field of bromine in iron by NMR/ON

Nuclear magnetic resonance of⁸²Br oriented at low temperature in iron has been observed with a sample prepared by ion implantation atT<0.2 K. The asymmetric resonance signal can be decomposed in a broad background signal and a narrow line of FWHM=1.8 (4) MHz which can be attributed to⁸²Br in undisturbed substitutional sites of Fe. From the center frequency of this narrow line (B _ext=0)=201.86(13) MHz we derive the magnetic hyperfine field asB _hf(BrFe)=81.38(6) T. This value is considerably larger than the result of theoretical calculations.     

Ferrocenasymmetrie, 4. Mitt.: Die Absolutkonfiguration von (β- und γ-Phenyl-α-ketotetramethylen)-ferrocen

Zusammenfassung Ringschluß von -bzw. -Phenyl--ferrocenyl-buttersäure liefert die homoannular überbrückten Ketone (- bzw. -Phenyl--ketotetramethylen)-ferrocen (VI, VII, XIV). Die Ermittlung der Absolutkonfiguration dieser Ketone gelang durch Korrelation des Asymmetriezentrums der optisch aktiven -Phenyl--ferrocenyl-buttersäure (deren Absolutkonfiguration primär bestimmt wurde) mit der Konfiguration des planar asymmetrischen Anteils in den optisch aktiven Ketonen.Die erhaltenen Ergebnisse waren auch mit der früher für (+)-1,2-(-Ketotetramethylen)-ferrocen (I) auf unabhängigem Weg ermittelten Konfiguration in Einklang, wie durch Messung des optischen Circulardichroismus erwiesen werden konnte: die rechtsdrehenden Enantiomeren besitzen die (R), die linksdrehenden (S)-Konfiguration.

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Ring closure of - and -phenyl--ferrocenylbutyric acid yielded the corresponding homoannularily bridged ketones, (- and -phenyl--ketotetramethylene)-ferrocene (VI, VII, XIV), respectively. The absolute configuration of these ketones could be established by correlation of the asymmetric center of the optically active -phenyl--ferrocenylbutyric acid (whose absolute configuration was determined previously) with the configuration of the planar asymmetric part in the optically active ketones.The results obtained support the configuration reported earlier for (+)-1,2-(-ketotetramethylene)-ferrocene (I) and established by an independent route. The configurations could also be supported by use of optical circular dichroism, i. e., the dextrorotatory enantiomers have the (R)-configuration, the laevorotatory the (S)-configuration.

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Mit 1 Abbildung

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Über die Verwendung des Ausdruckes Ferrocen-Chiralität (bzw. Chiralitäts-Zentrum und Planar-Chiralität) vgl., Fußnote S. 266.

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Vgl. hierzu die Fußnote auf S. 1066

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3. Mitt. über Ferrocenasymmetrie, zugleich 24. Mitt. über Ferrocenderivate:H. Falk undK. Schlögl, Mh. Chem.96, 266 (1965).     

Biphenyl-tricarbonylchrom-komplexe, 9. Mitt.: Synthesen,chromatographische Enantiomerentrennung,Circulardichroismus und Chiralität von mono- und bis-(Tricarbonylchrom)-Komplexen di- und tetrasubstituierter sowie überbrückter Biphenyle

Chiral title compounds have been resolved by medium pressure liquid chromatography (MPLC) on triacetylcellulose in ethanol. Whereas a quantitative separation was achieved for16 and20, a recycling technique had to be applied to1,4,6,10 and15 leading to a 100% e.e. for1,6 and15 and to ca. 60% e.e. for4 and10.An unambiguous assignment of the chirality (+)-(R) _a -(S) _m for tricarbonylchromium-6,6-dimethyl-diphenicacid dimethylester (4) was deduced both from the photochemical decomplexation to (-)-5 with the known chirality (R) _a (whose e.e. was determined by MPLC on triacetylcellulose) and by comparison of the¹H-n.m.r. spectra of4 and5 thereby proving the structure 4 for the former.Other chiralities both for mono and bis(tricarbonylchromium)biphenyl complexes were established by chemical correlations and comparison of the CD spectra with those of key compounds.

Herrn Prof. Dr.H. Tuppy mit besten Wünschen zum 60. Geburtstag gewidmet.