engleski

Estimation of Stability Constants of Copper(II) and Nickel(II) Chelates with 1, 2-Diaminoethanes by the Overlapping Spheres Method

The method of overlapping spheres (OS) was applied for the estimation of stability constants (log K1) of copper(II) and nickel(II) mono-complexes with 1, 2-diaminoethane and its N-alkylated, N, N-dialkylated, and C-substituted derivatives. The central sphere, with the radius 3 or 4 &Aring ; ; ; ; ; , was situated at the central atom, or in the equatorial (N1 or N2) or apical position (X1 or X2). The overlapping volumes of the central sphere and the van der Waals spheres of the surrounding atoms were calculated, and correlated on the stability constants measured at two temperatures, 0 and 25°C. The regression analysis included the training set consisted of 14 ligands, subsequently divided into three subsets (classes), consisted of 5, 5, and 4 ligands. The general multivariate model including all the experimental data, i.e. log K1 for Cu(II) and Ni(II) complexes measured at 0 and 25°C (N=56), was developed by introducing two indicator variables. Predictive power of the best models was tested on stability constants of five copper(II) diamine chelates with highly variable structure, yielding the reproduction of experimental data with an error 0.02 - 0.75 (rms = 0.34) log K units.

coordination compounds; molecular volumes; indicator variable; CROMRsel prodedure

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