title: Thermodynamic study of dihydrogen phosphate dimerisation and complexation with novel urea- and thiourea-based receptors.
abstract: Complexation of dihydrogen phosphate by novel thiourea and urea receptors in acetonitrile and dimethyl sulfoxide was studied in detail by an integrated approach by using several methods (isothermal titration calorimetry, ESI-MS, and (1)H NMR and UV spectroscopy). Thermodynamic investigations into H2PO4(-) dimerisation, which is a process that has been frequently recognised, but rarely quantitatively described, were carried out as well. The corresponding equilibrium was taken into account in the anion-binding studies, which enabled reliable determination of the complexation thermodynamic quantities. In both solvents the thiourea derivatives exhibited considerably higher binding affinities with respect to those containing the urea moiety. In acetonitrile, 1:1 and 2:1 (anion/receptor) complexes formed, whereas in dimethyl sulfoxide only the significantly less stable complexes of 1:1 stoichiometry were detected. The solvent effects on the thermodynamic parameters of dihydrogen phosphate dimerisation and complexation reactions are discussed.
authors.affiliation: Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, Zagreb (Croatia).
authors.forename: Nikola
authors.initials: N
authors.lastname: Bregović
authors.forename: Nikola
authors.initials: N
authors.lastname: Cindro
authors.forename: Leo
authors.initials: L
authors.lastname: Frkanec
authors.forename: Krunoslav
authors.initials: K
authors.lastname: Užarević
authors.forename: Vladislav
authors.initials: V
authors.lastname: Tomišić
keywords: anions; dimerisation; receptors; solvent effects; thermodynamics