Tetrathiafulvalene diindolylquinoxaline: a dual signaling anion receptor with phosphate selectivity

Abstract

Incorporation of tetrathiafulvalene into the backbone of a known neutral phosphate receptor, diindolylquinoxaline, yields a dual optical-electrochemical chemosensor for dihydrogen phosphate that functions in dichloromethane. This system shows selectivity for dihydrogen phosphate over other small anions and can be used to detect the presence of this analyte via fluorescence quenching or cyclic voltammetry.

Fig. 1

Single crystal X-ray structure of 1·TBA·H₂PO₄. Top: view of the 2 : 2 complex formed between the receptor and the bound anion. The TBA counter cations have been omitted for clarity and the thermal ellipsoids are scaled to 30% probability level. Bottom: view showing the extended one-dimensional dihydrogen phosphate network within the crystal.

Fig. 2

(a) Fluorescent emission spectra of 1 (2.0 × 10⁻⁶ M) recorded in dichloromethane (λ_ex = 468 nm) before and after the addition of up to 50 equiv. of TBA·H₂PO₄. (b) Fluorescent emission spectra of receptor 1 (1.5 × 10^–6 M) recorded upon the addition of 50 equiv. of various tetrabutylammonium anion salts in dichloromethane (λ_ex = 468 nm).

Fig. 3

Cyclic voltammograms of receptor 1 (2.5 × 10⁻⁴ M) recorded in dichloromethane at 298 K with TBA·PF₆ (0.3 M) as the supporting electrolyte in the presence of TBA·H₂PO₄. The potentials were referenced to Ag/AgCl.

Scheme 1

Synthesis of receptor 1.

Scheme 1

Synthesis of receptor 1.