Complexation and Transport of Alkali and Alkaline Earth Metal Cations byp-tert-Butyldihomooxacalix[4]arene Tetraketone Derivatives

Abstract

The binding properties of three p-tert-butyldihomooxacalix[4]arene tetraketone derivatives (tert-butyl 2b, adamantyl 2c and phenyl 2d) in the cone conformation and one derivative (methyl 2a) in a partial cone conformation, towards alkali and alkaline earth metal cations have been established by extraction studies of metal picrates from water into dichloromethane, stability constant measurements in methanol and acetonitrile, and by 1 H NMR spectrometry. Transport experiments of metal picrates through a dichloromethane membrane were also performed. The results are compared to those obtained with closely-related calix[n]arene derivatives (n 5 4 and 5) and discussed in terms of the substituents, size and conformational effects. Methylketone 2a is a poor binder for all the cations studied, due to its partial cone conformation. Ketones 2b, 2c and 2d show high extraction and complexation levels for the alkali cations, with similar profiles and preference for K 1 and Na 1 (plateau selectivity). Towards alkaline earth cations, these ketones show a strong peak selectivity for Ba 21 in extraction, but a plateau selectivity for Ca 21 , Sr 21 and Ba 21 in complexation. The nature of the substituent attached to the ketone function has some influence on their binding properties, with phenylketone 2d being a slightly weaker binder than ketones 2b and 2c. 1 H NMR titrations confirm the formation of 1:1 complexes between the ketones and the cations studied, also indicating that they should be located inside the cavity defined by the phenoxy and carbonyl oxygen atoms. Ketones 2b, 2c and 2d show transport rates that do not follow, in general, the same trends observed in extraction and complexation.

Oligoether‐Strapped Calix[4]pyrrole: An Ion‐Pair Receptor Displaying Cation‐Dependent Chloride Anion Transport

“…Compounds 2 and 3 were synthesized by using slightly modified procedures previously reported in the literature. [11,16] All titrations (UV/Vis, fluorescence and ITC) were performed by using HPLC-grade CH 3 CN purchased from Aldrich.…”

Complexation and transport of transition and heavy metal cations by p-tert-butyldihomooxacalix[4]arene tetraketones and X-ray crystal structure of the tert-butyl ketone derivative

“…In the course of the studies of alkali and alkaline earth metal cation complexation and transport properties of dihomooxacalix [4]arenes bearing carbonyl groups at the lower rim, we have extended our research into transition and heavy metal ions. [16][17][18][19] This paper reports the binding properties of four tetraketone (methyl 2a, tert-butyl 2b, adamantyl 2c and phenyl 2d) derivatives of p-tert-butyldihomooxacalix [4]arene (1) towards transition (Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ ) and heavy (Ag + , Cd 2+ , Hg 2+ and Pb 2+ ) metal cations. These properties have been assessed by extraction studies of metal picrates from an aqueous solution into dichloromethane, transport experiments with the same salts through a dichloromethane membrane and stability constant measurements in methanol and acetonitrile based on UV absorption spectrophotometry.…”

Binding Properties and Molecular Mechanics Calculations ofp-tert-Butylhexahomotrioxacalix[3]arene Tri(diethyl)amide with Alkali, Alkaline Earth, Transition and Heavy Metal Cations

“…For the ArCH 2 Ar bridges, the variation in chemical shifts experienced by the equatorial methylene protons is downfield and much smaller than that of the axial protons, but the ArCH 2 OCH 2 Ar bridges behave differently, as reported previously [21,26,27]. The axial and equatorial methylene protons of the oxygen bridge move upfield and the equatorial protons experience larger shift variations than the axial ones.…”

“…It has been observed that the chemical shift changes of the methylene protons of the OCH 2 CO groups in dihomooxacalix [4]arene amide [26] and ketones [27,36] derivatives is upfield for the monovalent and downfield for the divalent cations. A closer examination of the spectral changes upon complexation indicates that triamide 1b behaves in a similar way.…”