Issue 7, 2001

Unusual conformational control of mobile mono- and diionizable calix[4]areneligands by alkali metal cations

Abstract

Conformations adopted in CDCl3 solution by alkali metal salts of mobile calix[4]arene ligands with one and two pendent proton-ionizable groups have been studied by NMR spectroscopy. For a series of the ligands with two N-(R-sulfonyl)carbamoylmethoxy substituents, there is no significant change in the conformational preferences of the calix[4]arene unit upon variation of the NSO2R substituents. Systematic changes of the preferred conformation(s) for the calix[4]arene moiety from cone to partial cone to 1,3-alternate are observed for all five of the ligands as the alkali metal cation is varied from Li+ to Na+ to K+ to Rb+ to Cs+. For ligands with one proton-ionizable group [carboxylic acid or N-(trifluoromethylsulfonyl)carboxamide] the conformational preferences of the calix[4]arene unit are also controlled by the identity of the complexed metal ion. The Li+ salts prefer the cone conformation, while for the Na+ and K+ salts more than two significantly populated conformations are evident. Remarkably, Cs+ and Rb+ salts prefer a partial cone conformation, which provides the possibility for the metal ion to have three π-interactions with the arene units of the calix[4]arene moiety and a coulombic interaction with the ionized group.

Graphical abstract: Unusual conformational control of mobile mono- and diionizable calix[4]arene ligands by alkali metal cations [ ]  [ ]

Supplementary files

Article information

Article type
Paper
Submitted
07 Feb 2001
Accepted
10 May 2001
First published
06 Jun 2001

J. Chem. Soc., Perkin Trans. 2, 2001, 1103-1108

Unusual conformational control of mobile mono- and diionizable calix[4]arene ligands by alkali metal cations

V. S. Talanov, H. Hwang and R. A. Bartsch, J. Chem. Soc., Perkin Trans. 2, 2001, 1103 DOI: 10.1039/B101232K

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Spotlight

Advertisements