Naphthyl- <i>vs</i>. anthrylpyridine-2,6-dicarboxamides in cation binding studies. Synthesis and spectroscopic properties

<p>Pyridine-2,6-carboxamides bearing α- or β-naphthyl- and α- or β-anthryl residues were prepared using simple method from pyridine-2,6-carboxylic acid dichloride and the respective aromatic amines. For the obtained receptors, selective binding of lead(II) and copper(II) was found. Ion–receptor interactions were studied using UV–vis spectroscopy, spectrofluorimetry, ¹H NMR and FTIR spectroscopy. The reversible lead(II) and copper(II) binding was discussed in regard of type of aromatic residue and amide bond localisation in aromatic ring, and binding model was proposed.</p

Dendronized Polymers with Silver and Mercury Cations Recognition: Complexation Studies and Polyelectrolyte Behavior

Metal binding properties of a series of worm-like dendronized polymers bearing oxathiaether-based dendrons are reported. Extensive characterization of the complexation properties toward a large range of metal cations showed a high and selective affinity of the polymers for Ag⁺ and Hg²⁺ cations. Its origin is explained by the presence of specific M···S and M···O interactions (M = Ag⁺ or Hg²⁺) within a cage structure formed by the dendritic moiety. The stoichiometry of the complexation is found to be affected by the degree of steric constraints in the dendronized materials. The effect of Ag⁺ complexation leads to the appearance of polyelectrolyte/charged colloid properties which were intensively studied by SANS. A significant result is the absence of major modification of the (spherocylinder) shape of the polymers upon Ag⁺ sequestration which confirms the above mentioned complexation scenario. Another outstanding result of Ag⁺ complexation is the Coulombic stabilization of the charged denpols that drastically affects their thermoresponsive properties (sharp elevation of LCST), indicating possible chemosensing applications

Bidentate Urea Derivatives of <i>p‑tert</i>-Butyldihomooxacalix[4]arene: Neutral Receptors for Anion Complexation

Three new bidentate ureidodihomooxacalix[4]­arene derivatives (phenyl <b>5a</b>, <i>n</i>-propyl <b>5b</b>, and <i>tert</i>-butyl <b>5c</b>) were synthesized in four steps from the parent compound <i>p-tert</i>-butyldihomooxacalix­[4]­arene and obtained in the cone conformation, as shown by NMR studies. The binding ability of these neutral receptors toward spherical, linear, trigonal planar, and tetrahedrical anions was assessed by ¹H NMR and UV–vis titrations. The structures and complexation energies of some complexes were also studied by DFT methods. The data showed that the association constants are strongly dependent on the nature of the substituent (aryl/alkyl) at the urea moiety. In general, for all the receptors, the association constants decrease with decrease of anion basicity. Ph-urea <b>5a</b> is the best anion receptor, showing the strongest complexation for F^– (log <i>K</i>_assoc = 3.10 in CDCl₃) and also high binding affinity for the carboxylates AcO^– and BzO^–. Similar results were obtained by UV–vis studies and were also corroborated by DFT calculations