Metal cation-ligand interactions of catechols of biological importance—I. Stability of iron(III) dihydroxybenzamide complexes which are related to cephalosporins bearing at C3′ a catechol group

摘要: Abstract Iron-chelating properties have been studied with N-ethyl-3,4-dihydroxybenzene-sulphonamide and 5-substituted dihydroxybenzamides as model molecules of β-lactam antibiotics to which are attached similar derivatized catechols. Acidity constants the ligands equilibrium iron(III) complexes determined by potentiometry spectrophotometry at 25°C 1 mol dm −3 ionic strength (NaClO 4 ). The formation show that these form exceptionally stable (log β 3 ⋍ 40) ferric ion, is coordinated through two phenolic oxygens catechol group. No precise correlation between stability Fe 3+ in vitro microbiological has made. However, it appears most potent those bearing substituted catechols possessing highest chelating lowest p K a values.