Darstellung und EPR-spektroskopie m-phenylen-verknuepfter biradikalischer bistetracyclon-metallketyle
作者:H. Kurreck、S. Obstreich
DOI:10.1016/s0040-4020(01)97574-x
日期:1974.1
From the corresponding metal ketyls—obtained by alkali metal reduction—EPR triplet powder spectra have been recorded. The spectra can be interpreted in terms of electron-electron dipolar coupling between the unpaired spins of randomly oriented molecules. The influences of substitution, concentration of the paramagneticspecies and of the nature of the alkali metal counter ion on the magnitude of the
Conformational subtlety in large polyphenylene molecules
作者:Robert A Pascal、Naoto Hayashi、Douglas M Ho
DOI:10.1016/s0040-4020(01)00238-1
日期:2001.4
1,3-Bis(nonaphenyl-3-biphenylyl)benzene (3), a large polyphenylene molecule (C138H94), was prepared by the Diels-Alder addition of 2 equiv. of 1-(pentaphenylphenyl)-2-phenylacetylene to 1,3-bis(3-oxo-2,4,5-triphenylcyclopenta-1,4-dienyl)benzene, and its X-ray structure was determined. The experimental structures of decaphenylbiphenyl (4) and 3 were compared with calculated structures of these molecules obtained by using methods ranging from molecular mechanics to hybrid density functional theory. Surprisingly, none of the computational methods examined correctly predicted the experimentally observed conformations of both 3 and 4. (C) 2001 Elsevier Science Ltd. All rights reserved.