Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5277066 | Tetrahedron Letters | 2007 | 5 Pages |
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 ÎGâ¡Â = 39.2 kJ/mol followed by a second one with a ÎGâ¡ 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.
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