Abstract
The redox properties of the title mono- and binuclear copper(II) chelates have been investigated by cyclic voltammetry in DMF at a working platinum electrode. The cathodic reduction and anodic oxidation of the investigated chelates produced the corresponding electrochemical Cu^sup I^ and Cu^sup III^species stable only in the voltammetric time scale, The effects of substituents on E^sub 1/2^, redox properties and stability towards oxidation of the complexes were related to the electron-withdrawing or releasing ability of the substituents on the C=N^sup 1^[H, CH^sub 3^ or C^sub 6^H^sub 5^] and/or N^sup 4^H [H, C^sub 2^H^sub 5^, C^sub 6^H^sub 5^ or pClC^sub 6^H^sub 4^] groups, The electron attracting substituents stabilize the Cu(II) complexes while electron-donating groups favor oxidation to Cu(III). Changes in the E^sub 1/2^ for the complexes due to remote substituent effects could be related to changes in basicity of N^sup 4^H.Thus, variation in N^sup 4^1-J has more influence on E^sub 1/2^ than changes in C=N^sup 1^. The correlation between E^sub 1/2^ of the complexes and pK^sub a^ of the ligands has been attributed to the spherical potential generated by the electron density of the donor atoms at the antibonding d orbitals.[PUBLICATION ABSTRACT]