Kinetically stable complexes of alkali cations with rigidified calix[4]arenes. X-ray structure of a calixspherand sodium picrate complex

Abstract

In this communication we describe the synthesis of a novel class of highly preorganized host molecules in which the structural features of the calix[4]arenes and spherands are combined (calixspherand a), together with the complexation with alkali cations. The hexa-anisyl spherand 1 represents a macrocyclic host with an enforced cavity in which Li+ or Na+ cations are complexed with a very high thermodynamic stability.' Cram and co-workers have shown that these complexes of 1 with Li+ and Na+ are also kinetically very stable. However, the scope of complexation is Organic Chemistry,

Ab Initio Calculated Structures and Vibrational Spectra of 1,3-Diethoxy-p-tert-butylcalix[4]crown-5-ether Complexed with Potassium Cation

“…The number of cation-oxygen interactions in crown-5-ether ring and ethoxy groups with potassium cation was crucial to the stability of the different conformation of 2+K + complex. Theoretical infrared (IR) absorption spectra were calculated for the 1,3-diethoxy-p-tert-butylcalix [4]crown-5-ether (2) in the cone isomer and its alkali-metal-ion complexes. The vibrational frequencies for the host molecule 2cone are compared with those of its complexes (2cone+K + and 2pc+K + ), and found that the calculated results agree well with the structural features of the complexes.…”

“…[1][2][3] In particular the 1,3-dimethyl ether of p-tert-butylcalix [4]crown-5-ether (1) has shown a surprisingly high K + /Na + selectivity in extraction. 2 The complexation of alkali metal cations by conformationally rigid calix [4]crown ethers has been studied by 1 H NMR experiment, and X-ray crystal structures of 1,3-dialkoxycalix [4]crown-5-ether were reported. 4 Along with these efforts, a theoretical study of the stereochemical dependence of alkali metal ion complexation and liquid-liquid extraction of alkali cations by 1,3-dimethoxy-calix [4]crown-6-ether has been reported.…”

Functionalized calix[4]arenes as potential therapeutic agents

“…[42] Furthermore, similar strategies have been used to generate lower-rimbridged structures by reacting calix [4]arene with compounds having di-electrophilic sites. [43][44][45] Several examples have also been reported where porphyrins are quadruply attached to the lower/endo rim of calix [4]arene. [46][47][48] The functionalization of calixarenes at upper/exo rim in most cases has been carried out using p-tert-butylcalixarenes as starting material due to its easy availability in a singlestep procedure from a few milligrams to many kilograms scale.…”

mPW1PW91 Calculated Relative Stabilities and Structures for the Conformers of 1,3-dimethoxy-p-tert-butylthiacalix[4]crown-5-ether

“…[1][2][3][4] In particular the 1,3-dimethyl ether of p-tert-butylcalix [4] crown-5-ether (1) has shown a surprisingly high K + /Na + selectivity in extraction. 5 Thiacalix [4]arenes in the presence of sulfur atoms instead of methylene groups exhibit novel structural and functional features including easy oxidation of sulfur bridges and extra binding sites, which make these compounds very interesting with potential applications such as inclusion of a variety of guest molecules, recognition of metal ions, chiral recognition, novel anion receptors, and novel dendriticshelled molecular receptors. [6][7][8][9][10][11][12][13][14][15] Therefore, one of the obvious classes of ionophores suitable for selective complexation of alkali metal 522 김광호 ․ 최종인…”