Synthesis, spectroscopy, magnetic and redox behaviors of copper(II) complexes with tert-butylated salen type ligands bearing bis(4-aminophenyl)ethane and bis(4-aminophenyl)amide backbones

New salen type ligands, N,N′-bis(X-3-tert-butylsalicylidene)-4,4′-ethylenedianiline [(X = H (1), 5-tert-butyl (2)] and N,N′-bis(X-3-tert-butylsalicylidene)-4,4′-amidedianiline [X = H (3), 5-tert (4)] and their copper(II) complexes 5–8, have been synthesized. Their spectroscopic (IR, 1H NMR, UV/vis, ESR) properties, as well as magnetic and redox-reactivity behavior are reported. IR spectra of 7 and 8 indicate the coordination of amide oxygen atoms of 3 and 4 ligands to Cu(II). The solid state ESR spectra of 5–8 exhibits less informative exchange narrowed isotropic or anisotropic signals with weak unresolved low field patterns. The magnetic moments of 5 (2.92 μB per CuII) and 6 (2.79 μB per CuII) are unusual for copper(II) complexes and considerably higher than those for complexes 7 and 8. Cryogenic measurements (300–10 K) show weak antiferromagnetic exchange interactions between the copper(II) centers in complexes 6 and 8. The results of electrochemical and chemical redox-reactivity studies are discussed.

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► New N,N-bis(X,3-t-butylsalicylidene) separated by bis(4-aniline)ethane/amide ligands Cu(II) complexes.
► Spectroscopic characteristics of all compounds.
► Effect of linkers on the magnetic moments of Cu(II) complexes.
► Chemical oxidation of synthesized compounds.