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8431991 
Journal Article 
1002. The stability of metal complexes of 1,10-phenanthroline and its analogues. Part I. 1,10-Phenanthroline and 2,2′-bipyridyl 
Irving, H; Mellor, DH 
1962 
Yes 
Journal of the Chemical Society
ISSN: 0368-1769 
5222-5237 
English 
Methods suitable for determining the step-stability constants of very stable complexes of transition metals with 1,10-phenanthroline and its analogues are reviewed. Partition coefficients for 2,2′-bipyridyl and 1,10-phenanthroline between aqueous buffers of ionic strength 0.1M and chloroform, carbon tetrachloride, and n-hexane have been measured at 25°. From measurements of the distribution of the two ligand bases between these solvents and aqueous buffers containing known concentrations of various cations, step-stability constants, valid for 25° and 0.1M-potassium chloride (or nitrate) have been determined for bivalent ions of manganese, iron, cobalt, nickel, copper, zinc, and cadmium. The stabilities of the 1:1 complexes follow the Irving-Williams order in each case and they increase in the order Mn<Cd<Fe<Zn<Co<Ni<Cu. For the 3:1 complexes, however, the order becomes Mn<Cd<Zn<Co<Cu<Fe<Ni. The anomalous stability of the ferrous tris-complex is shown to arise because K3 is greater than both K1 and K2, owing to formation of a spin-paired complex.