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. 2021 Mar 10;11(17):10203-10211.
doi: 10.1039/d1ra01285a. eCollection 2021 Mar 5.

Carbazole sulfonamide-based macrocyclic receptors capable of selective complexation of fluoride ion

Na Luo  1 , Junhong Li  1 , Tao Sun  2 , Suran Wan  1 , Peijia Li  1 , Nan Wu  1 , Ya Yan  1 , Xiaoping Bao  1
Affiliations

Carbazole sulfonamide-based macrocyclic receptors capable of selective complexation of fluoride ion

Na Luo et al. RSC Adv. .

Abstract

Two carbazole sulfonamide-based macrocycles 1 and 2 were facilely synthesized and carefully evaluated for their anion recognition properties. The obtained results revealed that macrocycle 1 with a 1,3-xylyl linker was able to bind fluoride ion more strongly and selectively in acetonitrile medium than its strong competitors (like acetate and dihydrogen phosphate anions), with a large binding constant (K a) of 50 878 M-1. More importantly, an exclusive fluoride recognition was achieved for macrocycle 1 in the more polar DMSO-d 6 solution, albeit with a moderate affinity of K a = 147 M-1. Compared with macrocycle 1, macrocycle 2 bearing a 2,6-lutidinyl linkage exhibited a remarkable change not only in the anion affinity but also in the anion selectivity, although with only a slight difference in their molecular structures.

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Conflict of interest statement

There are no conflicts to declare.

Figures

Scheme 1
Scheme 1. Synthesis of macrocycles 1 and 2. Reaction conditions: (a) 1,3-xylenediamine/dry CH2Cl2/dry TEA/rt/30%; (b) 2,6-lutidinylenediamine/dry CH2Cl2/dry TEA/rt/25%.
Fig. 1
Fig. 1. Crystal structures of macrocycles 1 and 2.
Fig. 2
Fig. 2. (a) Stack plot of 1H NMR titration of macrocycle 1 (1.6 mM) with TBAF in CD3CN at 298 K. (b) Chemical shift changes of the proton Hc in 1 upon addition of TBAF in CD3CN (Ka > 10 000 M−1).
Fig. 3
Fig. 3. (a) Stack plot of 1H NMR titration of macrocycle 1 (1.6 mM) with TBAH2PO4 in CD3CN at 298 K. (b) Fitting binding isotherms of macrocycle 1 with TBAH2PO4 in CD3CN at 298 K, showing chemical shift changes of the proton Ha based on a 1 : 1 binding model.
Fig. 4
Fig. 4. UV-vis titration of macrocycle 1 (20 μM) with TBAF in CH3CN (Inset: A 1 : 1 non-linear curve fitting of the absorbance at 294 nm of macrocycle 1 against the added F−).
Fig. 5
Fig. 5. (a) 1H NMR titration of macrocycle 1 (1.6 mM) with TBAF in DMSO-d6. (b) Fitting binding isotherms of macrocycle 1 with TBAF in DMSO-d6 at 298 K, showing chemical shift changes of the proton Hc based on a 1 : 1 binding model.
Fig. 6
Fig. 6. Crystal structure of the formed complex between macrocycle 1 and fluoride ion. The counterion (TBA+) was omitted for clarity.
Fig. 7
Fig. 7. DFT-optimized structure of macrocycle 1/F− complex.
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