Chromogenic amides of pyridine-2,6-dicarboxylic acid as anion receptors

Influence of halogen-halogen interactions in the self-assembly of pillar[5]arene-based supramolecular polymers

Halogen-halogen interactions play a pivotal role in the formation and stability of supramolecular assemblies. Herein, we investigate the assembly dynamics and dissociation pathways of linear supramolecular polymers based on pillar[5]arene-mediated by guest halogen-halogen interactions (C-X × X-C) in both the solution and solid states. The structure of the solid-state supramolecular assembly was determined by single-crystal X-ray diffraction analysis. The binding affinities of four different 1,4-dihalobutane guests with pillar[5]arene were investigated by 1H NMR spectroscopic titration and isothermal titration calorimetry (ITC). The formation of the halogen-bonded linear supramolecular polymer in solution was demonstrated using diffusion-ordered spectroscopy (DOSY) and ITC. Our findings highlight the dependence of the dissociation process on halogen nature within the encapsulated guest, revealing that the process is entropically driven (TΔS = 27.12 kJ mol-1) and enthalpically disfavored (ΔH = 9.99 kJ mol-1). Moreover, the disassembly of supramolecular polymers promoted by N-containing compounds was investigated using 1H NMR spectroscopy and ITC, revealing that the process is driven both enthalpically (ΔH = -2.64 kJ mol-1) and entropically (TΔS = 15.70 kJ mol-1). Notably, the data suggest the formation of N⋯I bonding interactions at both ends of the inclusion guest, elucidating the intricate interplay of halogen interactions and host-guest chemistry in supramolecular polymer systems.

Spatially Designed Supramolecular Anion Receptors Based on Pillar[5]arene Scaffolds: Synthesis and Halide Anion Binding Properties

Urea-functionalized anion receptors based on brominated functionalized pillar[5]arenes were prepared. The binding affinity toward halide anions was investigated and probed using ¹H NMR titration and isothermal titration calorimetry (ITC). The complexation behavior was affected by the structure of the receptor and the nature of the anionic guest. The synthesized receptors are highly selective toward fluoride resulting in the formation of a 1:2 host-to-guest complex. The anion receptor based on the 1,3-alternate pillar[5]arene regioisomer shows the highest affinity toward fluorine anions. No significant interactions were observed with larger bromine anions. The formation of a self-assembled supramolecular polymer driven by hydrogen bonds in solution was demonstrated by diffusion-ordered spectroscopy (DOSY), ITC, and dynamic light scattering (DLS) measurements. From ITC dilution experiments, we found that the supramolecular polymer self-assembly at higher concentrations is a spontaneous process as indicated by the positive value of Gibbs free energy (ΔG = 12.04 kJ mol^-1).

Synthesis and Structural Characterization of Pyridine-2,6-dicarboxamide and Furan-2,5-dicarboxamide Derivatives

Derivatives based on pyridine-2-6- and furan-2,5-dicarboxamide scaffolds reveal numerous chemical properties and biological activities. This fact makes them an exciting research topic in supramolecular and coordination chemistry and in discovering new pharmacologically-active compounds. This work aimed to obtain a series of symmetrical pyridine-2-6- and furan-2,5-dicarboxamides through a condensation reaction of the appropriate acyl chlorides and aromatic amides. Successful syntheses were confirmed with NMR spectroscopy. We solved their crystal structures for seven compounds; two pyridine and five furan derivatives. Based on our crystallographic studies, we were able to indicate supramolecular features of the crystals under investigation. Additionally, Hirshfeld surface analysis allowed us to calculate a distribution of intermolecular contacts in the dicarboxamide crystals.

Ion recognition properties of new pyridine-2,6-dicarboxamide bearing propeller-like pendant residues: multi-spectroscopic approach

Abstract

The synthesis and ion binding properties of new amide derived from propeller-like tris(2-pyridyl)amine and 2,6-pyridinedicarboxylic acid chloride were described. Amide binds divalent metal cations: copper(II), nickel(II), zinc(II), and lead(II) in acetonitrile. In acetonitrile:water mixture (9:1 v/v) amide interacts only with copper(II) and nickel(II) cations forming complexes of 1:1 stoichiometry. It was found that the introduction of bulky, nitrogen donor atom bearing pendant groups can influence coordination mode of pyridine-2,6-dicarboxamides. The probable model of ligand-ion interactions is proposed on the basis of 1H NMR and FT-IR spectroscopy.

Graphic abstract

Anion binding by p-aminoazobenzene-derived aromatic amides: spectroscopic and electrochemical studies

The synthesis and complexing properties of p-aminoazobenzene-derived mono-, bis-, and trisamides were described. Ligands 3 and 4 bind anions, including fluorides, chlorides, bromides, acetates, benzoates, dihydrogen phosphates, hydrogen sulfates, and p-toluenesulfonates, in chloroform forming 1 : 1 complexes. The highest value of stability constant was evaluated for the 4-F^- complex (log K = 5.63 ± 0.21). On the basis of ¹H NMR, and FTIR spectroscopy, the possible nature of the ligand-anion interactions was proposed. The E ⇄ Z isomerization process of tripodal amide 4 in chloroform was studied. The effect of anions on Z to E thermal back isomerization was investigated.