Estimation of stability constants of copper(II) chelates with triamines and their mixed complexes with amino acids by using topological indices and the overlapping spheres method

Our two original approaches, the first based on the topological (connectivity) index 3χv and the second based on the model of overlapping spheres (OS), were applied for the estimation of stability constants of copper(II) complexes (CuL) with ethylenediamines (N = 14) and diethylenetriamines (N = 8), and mixed complexes (CuLA) of amino acids and diethylenetriamines (N = 18). The stability constants of the ethylenediamine complexes were predicted “indirectly” from calibration models developed on diethylenetriamines and vice versa, and also by a more direct method using the leave-one-out procedure of cross validation (cv). By averaging all the estimates, stability constants were reproduced with a rms error of 0.56 and 0.43 log K units for diethylenetriamines and ethylenediamines, respectively.Stability constants of the mixed complexes (CuLA) were estimated with S.E.cv = 0.69 log K units (the best linear regression) and S.E.cv = 0.53 log K units (the best binomial regression). The best bivariate regression with the indicator variable, In = 1 for CuLA, In = 0 for CuL, combining stability constants of CuL and CuLA, gave S.E.cv = 0.67 log K units.

Graphical abstractStability constants of Cu(II) chelates with ethylenediamines and diethylenetriamines, and their mixed complexes with amino acids were calculated from their connectivity indices, 3χv, and OS volumes, V∗, by using calibration models developed on the same or different classes of compounds.Figure optionsDownload full-size imageDownload as PowerPoint slide