Anion Responsive TTF-Appended Calix4arenes. Synthesis and Study of Two Different Conformers

摘要

Two new cone- and 1,3-alternate-calix[4]arenes (>cone-1 and >1,3-alt-1), bearing four modified TTF (tetrathiafulvalene) substituents on the upper rim, have been synthesized. The binding ability of these two sets of conformers for various anions, including F⁻, Cl⁻, Br⁻, I⁻, PF6⁻, ClO4⁻, HSO4⁻, CH3COO⁻, H2PO4⁻, and HP2O7³⁻, was tested in organic media by monitoring the changes in their UV/vis and ¹H NMR spectra as a function of added anion, as well as via cyclovoltammetry (CV) (all anions studied as their respective TBA salts). On the basis of the present findings, we propose that incorporation of four TTF units within an overall calix[4]arene-based recognition framework produces a preorganized receptor system that displays a modest preference for the pyrophosphate (HP2O7³⁻) anion.