Synthesis, Structures, and Conformational Characteristics of Calixarene Monoanions and Dianions

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• 作者：Tracy A. Hanna ; Lihua Liu ; Alfredo M. Angeles-Boza ; Xiaodi Kou ; C. David Gutsche ; Krzysztof Ejsmont ; William H. Watson ; Lev N. Zakharov ; Christopher D. Incarvito ; and Arnold L. Rheingold
• 刊名：Journal of the American Chemical Society
• 出版年：2003
• 出版时间：May 21, 2003
• 年：2003
• 卷：125
• 期：20
• 页码：6228 - 6238
• 全文大小：395K
• 年卷期：v.125,no.20(May 21, 2003)
• ISSN：1520-5126

文摘

The synthesis, complete characterization, and solid state structural and solution conformationdetermination of calix[n]arenes (n = 4, 6, 8) is reported. A complete series of X-ray structures of the alkalimetal salts of calix[4]arene (HC4) illustrate the great influence of the alkali metal ion on the solid statestructure of calixanions (e.g., the Li salt of monoanionic HC4 is a monomer; the Na salt of monoanionicHC4 forms a dimer; and the K, Rb, and Cs salts exist in polymeric forms). Solution NMR spectra of alkalimetal salts of monoanionic calix[4]arenes indicate that they have the cone conformation in solution. Variable-temperature NMR spectra of salts HC4·M (M = Li, Na, K, Rb, Cs) show that they possess similarcoalescence temperatures, all higher than that of HC4. Due to steric hindrance from tert-butyl groups inthe para position of p-tert-butylcalix[4]arene (Bu^tC4), the alkali metal salts of monoanionic Bu^tC4 exist inmonomeric or dimeric form in the solid state. Calix[6]arene (HC6) and p-tert-butylcalix[6]arene (Bu^tC6)were treated with a 2:1 molar ratio of M₂CO₃ (M = K, Rb, Cs) or a 1:1 molar ratio of MOC(CH₃)₃ (M = Li,Na) to give calix[6]arene monoanions, but calix[6]arenes react in a 1:1 molar ratio with M₂CO₃ (M = K, Rb,Cs) to afford calix[6]arene dianions. Calix[8]arene (HC8) and p-tert-butylcalix[8]arene (Bu^tC8) have similarreactivity. The alkali metal salts of monoanionic calix[6]arenes are more conformationally flexible than thealkali metal salts of dianionic calix[6]arenes, which has been shown by their solution NMR spectra. X-raycrystal structures of HC6·Li and HC6·Cs indicate that the size of the alkali metal has some influence onthe conformation of calixanions; for example, HC6·Li has a cone-like conformation, and HC6·Cs has a1,2,3-alternate conformation. The calix[6]arene dianions show roughly the same structural architecture,and the salts tend to form polymeric chains. For most calixarene salts cation- arene interactions wereobserved.