摘要:

AbstractIncreasing numbers of investigations have been carried out on bridged aromatic compounds, the independence of which was very recently acknowledged in the class name “phanes”. Special attention is being attracted by the [2.2] metacyclophanes, whose molecular architecture raises many interesting theoretical questions, mainly with regard to intramolecular steric and electronic interactions. In the present progress report, a short description of the classification and nomenclature of the phanes is followed by a discussion of new physical and chemical aspects of the stereochemistry of [2.2]metacyclophanes and a number of related [2.2] phanes with other aromatic nuc

ISSN:0570-0833    

DOI:10.1002/anie.197200731

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractA substance on which X‐rays fall emits photoelectrons and Auger electrons. The energy spectra of the electrons emitted provide information about the electronic structure in the specimen, ranging from the innermost atomic levels and their dependence on the chemical environment to the molecular orbitals of the valence electrons and the band structure in solids. Electron spectra of this nature can now be recorded with high‐resolution instruments; their analysis offers new aspects for investigation of chemical composition. The method of electron spectroscopy developed for this purpose, which has now been developed to a high degree of perfection, will be referred to in the following discussion as ESCA (ElectronSpectroscopy forChemicalAnalys

ISSN:0570-0833    

DOI:10.1002/anie.197200831

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractA review of the various possible definitions of diradicals leads the authors to describe these systems as having two odd electrons in degenerate or nearly‐degenerate molecular orbitals. A study of the wave‐function for the two odd electrons shows that its form depends entirely on whether the diradical is homo‐ or heterosymmetric. Energy schemes are given in these two cases, as well as in the intermediate “non‐symmetric” case. The extent of zwitterionic character in diradical states is also investigated. This is followed by a discussion of intersystem crossing between singlet and triplet diradical states via spin‐orbit coupling and other mechanisms. The electronic matrix elements for spin‐orbit coupling are calculated and evaluated numerically for various model cases. It is then possible to establish general rules for favorable (electronic) intersystem crossing. In 1,3 or 1,4 diradicals its efficiency is estimated to be comparable with that in aromatics. The role of the electron‐nuclear hyperfine interaction in mixing singlet and triplet states, particularly in CIDNP, is explained.Finally the question of whether diradicals actually occur as secondary minima on potential energy surfaces is examined. Recent quantum‐mechanical calculations, in contradiction to some thermochemical and kinetic evidence, lead to flat singlet surfaces without

ISSN:0570-0833    

DOI:10.1002/anie.197200921

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractIn solvents of low polarity, salts containing a carbanion, e.g. fluorenylsodium, or a radical anion, e.g. coronenesodium, can exist as contact ion pairs or as solvent separated ion pairs. Particular interest attaches to the complexes of ion pairs with the strongly solvating, polydentate polyglycol dimethyl ethers (glymes) and with crown compounds. These systems can be studied by optical spectroscopy, NMR spectroscopy, and other methods.

ISSN:0570-0833    

DOI:10.1002/anie.197201121

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197201271

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197201281

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197201291

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197201301

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197201311

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197201331

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY