Original scientific paper

Estimation of Stability Constants with Connectivity Index: Development of Bivariate and Multivariate Linear Models for Copper(II) Chelates with Oligopeptides

Ante Miličević ; Institute for Medical Research and Occupational Health, Ksaverska c. 2, P. O. Box 291, HR-10000 Zagreb, Croatia
Nenad Raos ; Institute for Medical Research and Occupational Health, Ksaverska c. 2, P. O. Box 291, HR-10000 Zagreb, Croatia

Abstract

The equilibrium constants K₁,K_a andβ₁of 25 copper(II) complexes with di-(N = 15), tri-(N = 5), tetra-(N = 2), and pentapeptides (N = 3) were estimated by using linear models based on the valence connectivity index of the 3rd order (3χv). For the stability constant K₁ two kinds of models were developed: bivariate models, which divide a molecule into N- and C-terminal segments, and multivariate models, which treat the connectivity index of each chelate ring as a separate variable. The models proved equally successful, yielding fair reproduction of experimental log K₁ (S.E._cv = 0.16–0.19, max. error = 0.4). Overall deprotonation constant K_a was estimated from the 3χv, calculated for the whole molecule of the complex, with the addition of two indicator variables to distinguish various classes of ligands. In this way, the overall stability constant (log β₁ = log K₁–pK_a) was reproduced with the error<0.81 (S.E. = 0.31).

Keywords

topological indices; linear regression models; indicator variable; dipeptides; tripeptides; tetrapeptides; pentapeptides

Hrčak ID:

45464

URI

https://hrcak.srce.hr/45464

Publication date:

11.12.2009.

Visits: 1.461 *