Influence of substituents on the structure of Schiff bases Cu(II) complexes

Abstract The relationship between molecular conformation and substituent effects of salicylaldehyde Schiff-base Cu(II) complexes was explored. For this study, eight samples of the complexes Cu(Sal-X)2 (X = OMe, Me, H, F, Cl, Br, CF3 and CN) were obtained by reaction of Cu(OAc)2 with Schiff base ligands (Sal-X) derived from Salicydaldehyde, and their crystal structures were characterized by the X-ray diffraction technique. The QSPR methods were employed to achieve deeper insight into geometry structure of Cu(Sal-X)2. The results show that the main geometrical parameters of Cu(Sal-X)2 are dominated by the substituents on the aniline ring. That is, the dihedral angle τ1 between the Cu–O–N plane and O–C N plane increases with the increase of electron-donating effect and electron-withdrawing effect of substituents, whereas the electronic effect of substituents has the opposite effect on τ2, which is the dihedral angle between the aniline ring plane and C–N–Cu plane. Moreover, the bond length L Cu - N decreases with growing excited-state parameter σ cc e x σccex of substituents which enhances the energy of C–N bond.