Kojate complexes, stability constants

To put hydroxypyranonate and hydroxypyridinonate complexes in context, stability constants for kojate and l,2-dimethyl-3-hydroxy-4-pyridinonate complexes of Mg, Al, Fe, and Gd are compared with stability constants for complexes of these cations with a few other ligands in Table III. That these hydroxypyranonate and hydroxyp5rr-idinonate ligands form stable complexes is immediately apparent. In this section we shall present and discuss a generous, but far from... 

Comparisons of Stability Constants (Log K f for Selected Complexes of Kojate AND OF 1,2-Dimethyl-3-hydroxy-4-pyridinonate with Those for a Range of Other... 

In contrast to stability constants, there are very few data for enthalpies and entropies of complex formation for hydroxypyranonate and hydroxypyridinonate complexes. Early studies on zinc-maltolate (190) and first-row transition metal(II) complexes of kojate (191) gave estimates of enthalpies and entropies of formation from temperature variation of stability constants, though as accurate stability constant measurements are only possible over a rather short temperature range the Aff and AS values obtained cannot be of high precision. 

Stability Constants for Kojate Complexes m Water-Dioxan Mixtures... 

As shown in Table XIV, the stability constant for the meconate complex of UO is much higher than that for the corresponding kojate complex (log ifi(mec) — 11.8, log ifi(koj) = 7.1) (230). This behavior parallels that for the Zn complexes of this pair of ligands (log ifi(mec) = 7.3, log ifi(koj) — 5.0 cf. Section III.A.2 earlier), and in turn refiects a large difference in pAa values for meconic and kojic acids. 

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