Effect of substituents on complex stability aimed at designing new iron(III) and aluminum(III) chelators.
The solution equilibria of iron(III) and aluminum(III) with two classes of hard ligands (catechol, salicylic acid and their nitro-derivatives) have been reliably studied by potentiometric, spectrophotometric and NMR spectroscopy. The effect of the nitro substituent on the binding properties of catechol and salicylic acid has been examined thoroughly. The inductive and resonance properties of the substituent that, as expected, lower the basicity of the phenolic and carboxylic groups, lead to a general decrease in both protonation and complex formation constants. This decrease causes an increase in pM of between 0.2 and 1.1pM units for the nitro-substituted salicylates and of about 4 units for 4-nitrocatechol, with a significantly higher chelating efficacy. The influence of the substituent on catechol and salicylic acid is discussed in detail on the basis of conditional constants at pH 7.4.
Nurchi
Valeria Marina
VM
Dipartimento di Scienze Chimiche, Centro Interdipartimentale per lo Studio dei Metalli in Medicina, Cittadella Universitaria, 09042 Monserrato-Cagliari, Italy.
Pivetta
Tiziana
T
Lachowicz
Joanna Izabela
JI
Crisponi
Guido
G
D000535:Aluminum / Q000737:chemistry*; D002396:Catechols / Q000737:chemistry; D002614:Chelating Agents / Q000138:chemical synthesis* / Q000737:chemistry; D015195:Drug Design; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D020156:Salicylic Acid / Q000737:chemistry
D002396:Catechols; D002614:Chelating Agents; D008024:Ligands; D009942:Organometallic Compounds; D000535:Aluminum; D007501:Iron; D020156:Salicylic Acid