ISSN:
1572-8927
Keywords:
Thermodynamics of oxygen binding
;
Co(II) oxygen-carrier complexes
;
macrocyclic ligands
;
tetraazacyclopentadecane
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Aqueous solutions containing Co2+ and the macrocyclic ligand 1,4,8,12-tetraazacyclopentadecane (L) are able to bind reversibly molecular oxygen to form the species Co2L2O 2 4+ between pH 5 and 7. This species at pH greater than 8 is replaced by the complex Co2L2O2 (OH) 2 2+ whose concentration in the solution increases to about pH 10.5. At pH greater than 10.5, Co(II) exists totally in this μ-peroxobisydroxo complex. Both the above mentioned oxygenated forms suffer a relatively slow irreversible oxidation to Co(III). From oxygen binding curves, approximate values of the equilibrium constants were calculated for the addition of oxygen to CoL2+ to form the μ-peroxo and the μ-peroxo-bishydroxo complexes. The enthalpies of formation of this latter complex starting from both Co2+ or CoL2+ have been obtained by means of calorimetric measurements. The effects of the size of the macrocyclic ligand on the affinity and the enthalpy of oxygen binding have been considered.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00646289
Permalink
