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The unique properties observed for the unsymmetrical macrocyclic compounds with the highly distorted structure
Authors:Junko Morita  Nao Yoshida  Sayaka Yokokawa
Institution:a The school of Human Environmental Science, Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-Ku, Tokyo 112-8610, Japan
b Institute of Industrial Science, The University of Tokyo, 7-22-1 Roppongi, Minato-Ku, Tokyo 106-0032, Japan
Abstract:A new class of aza-macrocycles with the highly distorted structure was found to exhibit unique properties. These macrocycles react with various lithium salts to form lithium complexes and their lithium complexation reactions depend on a substituent on the macrocyclic ring; slower rates and larger equilibrium constants were observed for the macrocycle with a bulkier substituent. The irradiation of these macrocycles by UV light was found to lead to the isomerization, and the photoisomerization rate of macrocycle with the bulky substituent was much faster. The highly distorted structure of these macrocycles makes it much easier to change the conformation of macrocyclic skeleton and these macrocycles have a variety of conformations. The factors to govern this conformational change were therefore explored. The solvent effect was examined by 1H NMR spectroscopy, because these macrocycles have a strong intramolecular hydrogen bond in the ring. As a result, the solvent was found to have a big effect on the 1H NMR spectra of macrocycles that could be explained in terms of the conformational change of macrocycle. This finding suggests the solvent to be an important way of controlling the conformation.
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