Lower Rim (lower + rim)

Distribution by Scientific Domains

Selected Abstracts

Lower Rim Substituted p-tert -Butyl-Calix[4]arene.

ELECTROANALYSIS, Issue 17-18 2009

Abstract Tetrasubstituted p-tert- butylcalix[4]arene-thioamides (1,5) were applied as ionophores in ion-selective membrane electrodes (ISE) and were tested towards Pb-selectivity. The selectivity coefficients of the electrodes were determined. The tertiary calix[4]thioamides (1, 2) show remarkable selectivity for Pb(II) cations when compared with respectable calix[4]amides. The electrode membranes with those ligands are stable, the Pb-characteristics are close to nernstian within a wide linear range (,log c=6,1). Compounds 3,5, the secondary calix[4]thioamides form less stable electrode membranes. Complex formation constants of the ligands 1, 2, 3 and 5 with Pb(II) and some most interfering ions were determined. [source]

ChemInform Abstract: Synthesis of New Schiff Base p-tert-Butyl-calix[4]arene with Imine Units Spanning 1,3-Distal Positions on the Lower Rim.

CHEMINFORM, Issue 36 2002
Manoj Kumar
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Heterometallic CoIII,LnIII (Ln = Gd, Tb, Dy) Complexes on a p -Sulfonatothiacalix[4]arene Platform Exhibiting Redox-Switchable Metal-to-Metal Energy Transfer

Viktoriya Skripacheva
Abstract Nuclear magnetic relaxation along with pH metric data have been used to reveal pH-dependent heterometallic CoIII,LnIII (Ln = Gd, Tb, and Dy) complex formation on a p -sulfonatothiacalix[4]arene (TCAS) platform in aqueous solution. The previously obtained 1D and 2D 1H NMR spectroscopic and X-ray data prove the outer sphere binding of the CoIII block with the upper rim of TCAS, whereas the LnIII ion is coordinated with the phenolate groups of the lower rim of TCAS. The inclusive outer-sphere binding of CoIII tris(dipyridyl) and tris(ethylendiaminate) complexes with the upper rim of TCAS favors binding of the inner-sphere lanthanide ions through the lower rim of TCAS, whereas noninclusive binding of CoIII bis(histidinate) provides no effect on the binding of lanthanide ions. The emission properties of [Co(dipy)3]3+,LnIII (Ln = Gd, Tb, Dy) complexes indicate the quenching of 4f luminescence by the 3d block. This quenching can be switched off by electrochemical CoIII/CoII reduction with further switching on by reoxidation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Synthesis and Anion-Binding Properties of Novel Redox-Active Calixarene Receptors

Estelle Métay
Abstract A novel synthetic approach towards redox-active calixarene-based receptors is described in which ferrocene fragments were introduced at the lower rim through anion-binding urea or amide connections. These derivatives were prepared in one pot by treating an amine-containing calixarene with ferrocenecarboxylic acid in the presence of diphenylphosphoryl azide and diisopropylethylamine. This method allows a convergent approach to these receptors and is readily adaptable to the introduction of other urea substituents. The anion-binding properties of these artificial receptors have been revealed by NMR spectroscopy and thoroughly investigated by electrochemical methods. We have assessed the importance of the urea,phosphate bonds in the observed electrochemical response by studying receptors in which the ferrocene reporters and binding fragments are closely associated or fully disconnected through a long alkyl chain. The experimental results clearly show the utmost importance of ion-pairing effects in the electrochemical recognition process, which account for most of the transduction signal in organic apolar media. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Analysis of interaction modes in calix[4]arene,levofloxacin complexes by quantum methods

Alexandrine Lambert
Abstract Host,guest interactions between chiral calix[4]arenes and the antibiotic levofloxacin are analyzed on the basis of quantum mechanical calculations at the density functional (for model systems) and semi-empirical levels. The calix[4]arene macrocycle carries two (+)-isomenthyl groups attached to opposing phenyl groups at the lower rim and different substituents (R,=,H, CH3, tBu, CH2CHCH2, COCH3 and NO2) are considered at the upper rim. Nitro derivatives are expected to form ionized complexes whereas the other derivatives should form neutral complexes with a very low stability. Copyright © 2006 John Wiley & Sons, Ltd. [source]

25-Allyloxy-5,11,17,23-tetra- tert -butyl-26,27,28-trihydroxycalix[4]arene chloroform disolvate

Tobias Gruber
In the title solvated calixarene, C47H60O4·2CHCl3, the host chalice displays an almost undistorted cone conformation, stabilized by three strong O,H...O hydrogen bonds at the calixarene's lower rim. One chloroform solvent molecule is fixed in the calixarene cavity by C,H..., interactions, while the second is accommodated in a clathrate-like mode in elliptical packing voids. These voids are spanned by six host molecules connected via C,H..., contacts and van der Waals interactions. Within the crystal structure, one tert -butyl group of the calixarene host is disordered over two orientations, with occupancies of 0.884,(4) and 0.116,(4). Furthermore, both solvent molecules show disorder, with occupancies of 0.857,(2) and 0.143,(2) for the cavitate-type, and 0.9359,(17) and 0.0641,(17) for the clathrate-type chloroform solvent molecules. [source]

Synthesis of Novel Calix[4]arenocrowns via Ring-closing Metathesis

Lin-Gang LU
Abstract A series of novel calix[4]arenocrown derivatives 8a,8c in a cone conformation, in which the lower rim and the upper rim were connected via ring-closing metathesis (RCM) reaction have been synthesized in good yields, and their structures were characterized by 1H NMR, 13C NMR, IR, MALDI-TOF MS techniques and elemental analyses. [source]

Novel Pyrene-armed Calix[4]arenes through Triazole Connection: Ratiometric Fluorescent Chemosensor for Zn2+ and Promising Structure for Integrated Logic Gates

Lin-Na ZHU
Abstract Two novel pyrene-armed calix[4]arenes by triazole connection were synthesized using "click" chemistry. Compound 1 with two pyrene subunits appended to the lower rims of the calix[4]arene shows ratiometric fluorescence response toward Zn2+, and selective fluorescence quenching toward heavy metal ions such as Cu2+, Hg2+ and Pb2+; while compound 2 with one pyrene subunit exhibits significant fluorescence quenching toward Cu2+ and moderate quenching behaviour toward Hg2+. By utilizing the different fluorescence behavior of 1 toward Zn2+ and Cu2+, inhibition (INH) and not or (NOR) logic gates were established. [source]