Authors Komber, H. ; Stumpe, K. ; Voit, B.
Title The rotation of pentaphenylphenyl groups and their terminal phenyl groups: a variable-temperature 1H NMR study on an albatrossene and a three-bladed molecular propeller
Date 13.04.2007
Number 14787
Abstract Dynamic NMR of 1-phenylethynyl-3,5-bis(pentaphenylphenyl)benzene (1) and 1,3,5-tris(pentaphenylphenyl)benzene (2) allows us to determine two rotational barriers for each compound. For 1, a first process exhibits ·G‡ = 39.2 kJ/mol followed by a second one with a ·G‡ value of 69.9 kJ/mol. Two processes with similar rotational barriers are found for 2 (70.9 and 75.3 kJ/mol). Motional processes which can be related to these barriers are 60° and 180° rotations of the pentaphenylphenyl units about the single bond with the core benzene ring and rotation of the terminal phenyl rings of the pentaphenylphenyl units. The results are discussed considering the consequences of these processes on the NMR spectra.
Publisher Tetrahedron Letters
Citation Tetrahedron Letters 48 (2007) 2655-2659
Tags conformational analysis dynamic nmr polyphenylenes oligophenylenes polycyclic aromatic-hydrocarbons polyphenylene dendrimers hyperbranched polyphenylenes crystal-structures cubic graphite hexaarylbenzenes oligophenylenes dynamics

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