Dehydroacetic Acid Derivatives Bearing Amide or Urea Moieties as Effective Anion Receptors

5 years ago

Dehydroacetic Acid Derivatives Bearing Amide or Urea Moieties as Effective Anion Receptors

Krunoslav Užarević, Vladislav Tomišić, Dajana Barišić, Branimir Bertoša, Nikola Cindro, Leo Frkanec, Nikola Bregović

Derivatives of dehydroacetic acid comprising amide or urea subunits have been synthesized and their anion-binding properties investigated. Among a series of halides and oxyanions, the studied compounds selectively bind acetate and dihydrogen phosphate in acetonitrile and dimethyl sulfoxide. The corresponding complexation processes were characterized by means of 1H NMR titrations, which revealed a 1:1 complex stoichiometry in most cases, with the exception of dihydrogen phosphate, which formed 2:1 (anion/ligand) complexes in acetonitrile. The complex stability constants were determined and are discussed with respect to the structural properties of the receptors, the hydrogen-bond-forming potential of the anions, and the characteristics of the solvents used. Based on the spectroscopic data and results of Monte Carlo simulations, the amide or urea groups were affirmed as the primary binding sites in all cases. The results of the computational methods indicate that an array of both inter- and intramolecular hydrogen bonds can form in the studied systems, and these were shown to play an important role in defining the overall stability of the complexes. Solubility measurements were carried out in both solvents and the thermodynamics of transfer from acetonitrile to dimethyl sulfoxide were characterized on a quantitative level. This has afforded a detailed insight into the impact of the medium on the complexation reactions. Come to bind: Amide or urea derivatives of dehydroacetic acid were synthesized and their anion-binding properties in MeCN and DMSO studied in detail by 1H NMR spectroscopy. Selectivity of the receptors towards H2PO4− and acetate was detected (see figure). Monte Carlo conformational searches assisted the interpretation of the experimental results. Thermodynamic characterization of receptor and complex solvation was carried out in both MeCN and DMSO, allowing for a deeper understanding of the effect of medium on the processes.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201701677