Original scientific paper

Estimation of Stability Constants of Copper(II) Chelates with N-alkylated Amino Acids using Topological Indices

Branka Grgas ; Institute for Medical Research and Occupational Health, Ksaverska c. 2, P.O.B. 291, HR-10001 Zagreb, The Republic of Croatia
Sonja Nikolić ; The Rugjer Bošković Institute, Bijenička c. 54, P.O.B. 1016, HR-10001 Zagreb, The Republic of Croatia
Nevenka Paulić ; Institute for Medical Research and Occupational Health, Ksaverska c. 2, P.O.B. 291, HR-10001 Zagreb, The Republic of Croatia
Nenad Raos ; Institute for Medical Research and Occupational Health, Ksaverska c. 2, P.O.B. 291, HR-10001 Zagreb, The Republic of Croatia

Abstract

Protonation (pK₁ and pK₂) and copper(II) binding stability constants (log β₁₁₀ and log β₁₂₀) of glycine and five N-alkylated glycines (methyl, dimethyl, diethyl, tert-butyl and tert-butylmethyl) were determined by potentiometric titration. These constants and the constants of eight N-alkylated glycinates, measured previously, were correlated with four topological indices (Wiener index, W, and the first-, second- and third-order valence-connectivity indices, 1χv, 2χv and 3χv) calculated for the ligand. The first protonation constants (ascribed to the dissociation of COOH group) do not correlate with any of the chosen topological indices (r2 < 0.3), but significant correlation was obtained for pK₂ (dissociation of amino group) with r2 values up to 0.920. »Corrected « stability constants (obtained by subtracting pK₂ value) yielded a generally better fit than the uncorrected ones. Our stability constants are better correlated with topological indices (max. r2 = 0.993) than the constants measured previously (max. r2 = 0.836). From the regression analysis it is possible to predict the values of pK₂, log β₁₁₀ and log β₁₂₀ with an error less than 0.1, 0.3 and 0.3 log units, respectively.

Keywords

Stability constants; Copper(II) chelates; N-alkylated glycinates; topological indices

Hrčak ID:

132307

URI

https://hrcak.srce.hr/132307

Publication date:

1.12.1999.

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