136734-88-8Relevant articles and documents
Dynamic factors in the design of redox-switched calix[4]arene cationophores
Bethell, Donald,Dougherty, Gary,Cupertino, Domenico C.
, p. 407 - 416 (2007/10/03)
Syntheses are described of four calix[4]arenes, each bearing a 9,10-anthraquinone moiety as a redox switch to modify cation binding. The first compound, having a triester-amide lariat-type structure, showed no experimental evidence (from cyclic voltammetry in acetonitrile solution) for enhancement of binding of alkalimetal cations, indicating negligible interaction between the binding site and the switchable group. Computer modelling showed that a large steric barrier prevents rotation of the switch into the energetically favourable position that would enhance cation binding. Compounds in which the anthraquinone formed part of a 1,3-bridging unit spanning the lower rim of the calix showed large cation-binding enhancements, the values being affected by the other, auxiliary groups on the lower rim of the calixarene. Unusual CV behaviour was observed in the case of the compound with two methoxy auxiliary donor groups in the presence of K+ , but not with Na+ . Computer modelling and NMR spectroscopic evidence indicates that this effect is attributable to a slow change of the calixarene from a cone to a partial cone conformation in binding K+, whereas the smaller Na+ fits easily into the available cavity of the cone conformation. Acta Chemica Scandinavica 1998.
Selective Monohydrolysis of Bridged and Unbridged Calixarene Esters and its Inhibition by Alkali Ion. Evidence for Hydronium Ion Complexation
Barrett, Geraldine,Bohmer, Volker,Ferguson, George,Gallagher, John F.,Harris, Stephen J.,et al.
, p. 1595 - 1601 (2007/10/02)
Several bridged and unbridged calixarene tetraester derivatives are hydrolysed by trifluoroacetic acid in chloroform with the loss of one, and only one, ester group to form triester monoacids.In bridged tetraethyl ester 11, the group that is hydrolysed is that on the aromatic moiety not carrying the methylene bridge.The hydrolysis process is inhibited by the presence of alkali metal cations, especially sodium.Evidence is presented in favour of a hydrolytic process involving hydronium ion complexation within the hydrophilic oxygenated cavity of the calixarene receptor.Crystals of the triester monoacid 5 were studied at 123 K and are monoclinic, space group P21/n, with four molecules in a cell of dimensions a = 13.554(6), b = 20.095(9), c = 20.658(17) Angstroem, β = 102.27(5) deg.The structure was solved by direct methods and refined by full-matrix least-squares calculations; R = 0.063 for 2017 observed reflections.The calixarene has a distorted cone conformation similar to that found in other closely related derivatives.The hydroxy group of the carboxylic acid moiety is hydrogen bonded to a proximal ethereal oxygen and not to carbonyl oxygen atoms.
Selective Monohydrolysis of a Calixarene Tetraethyl Ester with Trifluoroacetic Acid and its Inhibition by Na+ Ion: Evidence for Hydronium Ion Complexation
Boehmer, Volker,Vogt, Walter,Harris, Stephen J.,Leonard, Raymond, G.,Collins, Elizabeth M.,et al.
, p. 431 - 432 (2007/10/02)
Calixarene tetraethyl ester (1a) is hydrolysed by trifluoroacetic acid with the loss of one, and only one, ester group to form a monoacid triester; the process, which is inhibited by Na+ ion, is believed to involve specific hydronium ion complexation within the calixarene receptor.
