Original scientific paper

Estimation of Stability Constants of Copper(II) Bis-chelates by the Overlapping Spheres Method

Ante Miličević
Nenad Raos

Abstract

The method of overlapping spheres (OS) was applied for the estimation of stability constants (β2) of sets of (binary) copper(II) bis-complexes with 1,2-diaminoethanes (N = 14), aliphatic amino acids and their N-alkylated derivatives (N = 11), and naturally occurring amino acids (N = 9), along with a set of 16 mixed (ternary) copper(II) bis-complexes with naturally occurring amino acids. The central sphere, with the radius, Rv, 300 or 400 pm, was situated at the copper atom. The OS volumes (V*) of the central sphere and the van der Waals spheres of the surrounding atoms were calculated from the structures of bis- or corresponding mono-complexes
and correlated with the log β2 values. Both approaches yielded similar results, differing in the reproduction of stability constants by less than 20 %. Bivariate linear regression was performed
for mixed complexes, using (V*1 + V*2) and (V*1 – V*2) as independent variables (V*1 and V*2 correspond to the OS values for the two constituting chelate rings). The bivariate linear regression gave r = 0.961 and the reproduction of experimental data from 0.00 to 0.16 log β units (S.E.cv = 0.08 log β units).

Keywords

amino acids; 1,2-diaminoethanes; molecular volumes

Hrčak ID:

4159

URI

https://hrcak.srce.hr/4159

Publication date:

19.7.2006.

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