Alternatively, the charge and spin population of Cu was evaluated in terms of Quantum Theory of Atoms-in-Molecules (QTAIM)[17] (see Supplementary Information for details). The O → Cu electron density transfer was alternatively estimated as the Laplacian of the electron density (∇2ρ) at Cu – O bond critical points (BCP) using AIMAll software.[18] The MOLDRAW software[19] was used for geometry manipulation and visualisation purposes.
MIA is evaluated as the interaction energy
Eint = EcomplexECu(II) - EPh (1)
where E complex is the DFT energy of the2[Ph Cu]2+complex, E Cu(II) is the DFT energy of the Cu2+ ion and E Ph is the DFT energy of the p-substituted phenol molecule.
The standard linear regression analysis was used to obtain the regression parameters a and b of the relation
log (1/IC 50) = a X + b (2)
where log(1/IC 50) are the experimental toxicity data of Selassie et al .[2] and X stands for predictor variables under study. The goodness of fit is evaluated by standard statistical parameters such as the coefficient of determination R2 or the critical value α of the F-test.