• Duarte, Mt
• Freire, Cristina
• De Castro, B.
• Santos, Ic
• Vilas Boas, M.
• Piedade, Mfm

Abstract

The oxidative chemistry of three Ni(II) complexes with Schiff base ligands derived from salicylaldehyde and diamines with different steric demands, N,N'-2-methylpropane-2,3-diyl-bis(salicylideneiminate)nickel(II) (1), N,N'-1,2-cyclohexyl-1,2-dyil-bis(salicylideneiminate)nickel(II) (2) and N,N'-2,3-dimethylbutane-2,3-diyl-bis(salicylideneiminate)nickel(II) (3), was studied by cyclic voltammetry and chronoamperometry in N,N'-dimethylformamide and (CH3)(2)SO. The electrogenerated species were characterised by EPR spectroscopy. All three complexes exhibited metal-centred oxidised processes and the oxidised products were low-spin six-coordinate Ni(III) species (d(z2) ground state) with two solvent molecules axially coordinate. Addition of pyridine resulted in the replacement of solvent molecules with no changes in the ground state. The crystal structures of compounds 1 and 3 were determined from single crystal X-ray diffraction data, and the crystal packing for any of the complexes did not show any systematic parallel orientation of any part of the molecules. X-ray structural data for the Ni(II) complexes provided a rationale for the E-1/2 values obtained in the oxidation processes and for the relative energy of the low-lying excited duplets of the electrogenerated Ni(III) species.

Topics

• compound
• single crystal X-ray diffraction
• single crystal
• nickel
• electron spin resonance spectroscopy
• cyclic voltammetry
• chronoamperometry