| Abstract
| - Newp-tert-butylcalix[4]diquinones containing ester(1), amide (2−4), crown ether(5), and bis(veratrole) bridge (7)functionalities have been synthesized. The X-ray crystalstructures of 1-Sr(ClO4)2,1-KClO4, 2-NaClO4,4-n-BuNH3BF4,5-NaCO2CF3, and5-KPF6 have been elucidated. Theelectrochemical properties of the receptors have been studied and showthat these receptors can be used as electrochemical sensors forcaations.
- A new library of ionophoricp-tert-butylcalix[4]diquinones containing ester(1), primary, secondary, and tertiaryamide (2−4), and crown ether (5)substituents has been synthesized by treatment of the respective1,3-bis-substitutedp-tert-butylcalix[4]arene withTl(OCOCF3)3 in trifluoroacetic acid.The structures of the free ligands 1 and 2,ap-tert-butylcalix[4]diquinone bridged at thelower rim by two linked veratrole groups (7), and apreviouslysynthesized p-tert-butylcalix[4]diquinonebis(methyl ether) species (8) have been elucidated byX-ray crystallography. The X-ray crystal structures of1-Sr(ClO4)2,1-KClO4, 2-NaClO4,4-n-BuNH3BF4,5-NaOCOCF3, and5-KPF6 demonstrate that these complexes adoptthe cone conformation in the solid state. Interestingly,cation−quinone oxygen atom coordination occurs at both the upper and lower rimof 2-NaClO4 and4-n-BuNH3BF4.Solution coordination properties have been studied by both1H NMR and UV/vis techniques. Theelectrochemicalproperties of the “acyclic”p-tert-butylcalixdiquinones 1,4, and 8 and their complexes have been studiedusingcyclic and square wave voltammetric techniques. The reductionpotentials of the group 1 or 2 metal, ammonium,and alkylammonium complexes are significantly anodically shifted withrespect to that of the free ligand. Additionof cations to electrochemical solutions of ap-tert-butylcalixdiquinone−crown-5 compound (5)caused large anodicshifts (by up to 555 mV in the presence of Ba2+) in amanner similar to that of the acyclic species.
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