The synthesis of shape-persistentmacrocycles based on the phenyl-ethynyl backbone containing various extraannular alkyl side chains is described. Although compound solubility increases with increasing size of the side groups, decreasing the solvent polarity induces aggregation of the rings by nonspecific interactions. This was investigated by proton NMR spectroscopy. The magnitude of aggregation can
Rigid Phenylene Ethynylene Units Linked by A V-shaped Centre. An Approach to Biaxial Nematogens?
作者:Matthias Lehmann、Jérémy Levin
DOI:10.1080/15421400490435260
日期:2004.1
theoretical predictions that nematic phases formed from V-shaped compounds could be biaxial, shape-persistent phenylene ethynylene arms linked by 1,3-phenylene, 4,4′-diphenylenemethane and 3,6-fluorenone units have been synthesised. Crystallisation and micro-segregation is prevented by 2,5-alkoxy substitution on the middle benzene ring of the arms. The specific molecular engineering, i.e. variation
Oligo(phenyleneethynylene)s 1 are rod-like compounds with undisturbed conjugation. In supplementation of the previously described members of this series 1a−e, with repeating units of up to n = 5, this work contains the preparation of higher oligomers 1f−i (n = 6, 7, 8, 10) through the use of the Sonogashira−Hagihara reaction. Both the absorption and the fluorescence bands showed convergence for increasing