Synthesis, ESR, UV–Visible and reactivity studies of new bis(N-dimethoxyaniline-3,5-tBu2-salicylaldiminato)copper(II) complexes

Several new copper(II) complexes (4–6) with N-dimethoxyphenyl-3,5-tBu2-salicylaldimine ligands abbreviated as N-R-3,5-DTBS, where R = 2,4-dimethoxyphenyl (1), 2,5-dimethoxyphenyl (2) and 3,5-dimethoxyphenyl (3) have been prepared and their spectroscopic (IR, 1H NMR, UV/Vis, ESR), magnetic and redox reactivity are described. The ESR spectra of frozen-solution 4–6 and solid state 4 and 5 are indicative of axially symmetric g-tensor (g∥ > g⊥ > 2.03). The powder ESR spectrum of 6 is unusual for CuN2O2 type systems and exhibits “reversed” type (g∥ < g⊥) signal with a rhombic g-tensor g3 (2.235) > g2 (2.128) > g1 (2.019) pattern indicative of a dz2 ground state. Chemical oxidation of 4 and 6, as supported by ESR and UV/Vis techniques, generates new Cu(II) species and Cu(II)-phenoxyl radicals. The CV studies have shown that the complexes possess ligand-centered and copper(II)-centered quasi-reversible and irreversible responses.

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► New copper(II) complexes with N-di-(CH3O)Ph-3,5- tBu2-butylsalicylaldi-mines.
► For bis(N-3,5-di-CH3OPh-3,5-tBu2-salicylideneiminato)copper(II) g∥ < g⊥ was found.
► Chemical oxidations of bis(N-di-(CH3O)Ph-3,5-tBu2-salicylaldiminato) copper(II).