Iron(III) and aluminium(III) complexes with substituted salicyl-aldehydes and salicylic acids.
The chelating properties toward iron(III) and aluminium(III) of variously substituted salicyl-aldehydes and salicylic acids have been evaluated, together with the effect of methoxy and nitro substituents in ortho and para position with respect to the phenolic group. The protonation and iron and aluminium complex formation equilibria have been studied by potentiometry, UV-visible spectrophotometry and (1)H NMR spectroscopy. The overall results highlight that salicyl-aldehydes present good chelating properties toward iron(III), with pFe ranging from 14.2 with nitro to 15.7 with methoxy substituent, being ineffective toward aluminium; the pFe values for salicylic acids are generally lower than those for salicyl-aldehydes, and about 4 units higher than the corresponding pAl values. The effect of the two substituents on the chelating properties of the ligands can be rationalized in terms of the Swain-Lupton treatment which accounts for the field and resonance effects. The structural characterization of the 1:2 iron complex with p-nitro salicylic acid shows that iron(III) ion exhibits an octahedral surrounding where two salicylate chelating ligands supply two O-phenolate and two O-carboxylate donor atoms in a roughly equatorial plane. The trans-apical sites are occupied by two aqua ligands.
Dipartimento di Scienze Chimiche e Geologiche, Università di Cagliari, Cittadella Universitaria, 09042 Monserrato, Cagliari, Italy. Electronic address: nurchi@unica.it.
Valeria M
VM
Nurchi
Miriam
M
Crespo-Alonso
Leonardo
L
Toso
Joanna I
JI
Lachowicz
Guido
G
Crisponi
Giancarla
G
Alberti
Raffaela
R
Biesuz
Alicia
A
Domínguez-Martín
Juan
J
Niclós-Gutíerrez
Josefa M
JM
González-Pérez
M Antonietta
MA
Zoroddu
D000447:Aldehydes / Q000737:chemistry*; D000535:Aluminum / Q000737:chemistry*; D002614:Chelating Agents / Q000737:chemistry / Q000494:pharmacology; D056831:Coordination Complexes / Q000037:antagonists & inhibitors / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007501:Iron / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D011199:Potentiometry; D012459:Salicylates / Q000737:chemistry*; D020156:Salicylic Acid / Q000737:chemistry*; D013053:Spectrophotometry
D000447:Aldehydes; D002614:Chelating Agents; D056831:Coordination Complexes; D012459:Salicylates; D000535:Aluminum; D007501:Iron; D020156:Salicylic Acid
Al(III); Complex formation constant; Fe(III); Salicyl-aldehydes; Salicylic acid; X-ray structure