Kapinos, Larisa E. Song, Bin Sigel, Helmut <jats:title>Abstract</jats:title><jats:p> The stability constants of the 1:1 complexes formed between Mg<jats:sup>2+</jats:sup>, Ca<jats:sup>2+</jats:sup>, Sr<jats:sup>2+</jats:sup>, Ba<jats:sup>2+</jats:sup>, Mn<jats:sup>2+</jats:sup>, Co<jats:sup>2+</jats:sup>, Ni<jats:sup>2+</jats:sup>, Cu<jats:sup>2+</jats:sup>, Zn<jats:sup>2+</jats:sup> or Cd<jats:sup>2+</jats:sup> (= M<jats:sup>2+</jats:sup>) and 5,6-dichloro-l-(β-ᴅ-ribofuranosyl)benzim idazole (DRB) were determined by potentiom etric pH titrations in aqueous solution (25 °C; I = 0.5м, NaNO<jats:sub>3</jats:sub>). The acidity constant of H(DRB)<jats:sup>+</jats:sup>, the proton being at N3, was measured by the same method and the result was confirmed via spectrophotometry. Based on previously established [L. E. Kapinos, B. Song, H. Sigel, Inorg. Chim . Acta 280, in press (1998)] log<jats:sup>м</jats:sup><jats:sub>мʟ</jats:sub> versus K<jats:sup>ʜ</jats:sup><jats:sub>ʜʟ </jats:sub>straight-line plots for complexes of imidazole-type ligands it is shown for the Mn(DRB)<jats:sup>2+</jats:sup> and Zn (DRB)<jats:sup>2+</jats:sup> complexes, as examples, that the benzene ring of the benzim idazole residue exerts a steric inhibition for metal ion binding at N3; i.e., the data points for the M(DRB)<jats:sup>2+</jats:sup> complexes fall clearly below the straight lines defined by the imidazole- type ligands.</jats:p> https://sonar.ch/global/documents/231994 eng info:eu-repo/semantics/altIdentifier/doi/10.1515/znb-1998-0822 info:eu-repo/semantics/altIdentifier/issn/1865-7117 Zeitschrift für Naturforschung B. - Walter de Gruyter GmbH. - 1998, vol. 53, no. 8, p. 903-908 General Chemistry Metal Ion-Binding Properties in Aqueous Solution of the Nucleoside Analogue, 5,6-Dichloro-1-(β-ᴅ-ribofuranosyl)benzimidazole (DRB) http://purl.org/coar/resource_type/c_6501