Template condensation of 3,5-di-tert-butyl-2-hydroxybenzaldehyde S-methylisothiosemicarbazone with pentane-2,4-dione and triethyl orthoformate at elevated temperatures resulted in metal complexes of the type M^IIL, where M = Ni and Cu and H₂L = a novel tetradentate ligand. These complexes are relevant to the active site of the copper enzymes galactose oxidase and glyoxal oxidase. Demetalation of Ni^IIL with gaseous hydrogen chloride in chloroform afforded the metal-free ligand H₂L. Then by the reaction of H₂L with Zn(CH₃COO) ₂•2H₂O in a 1:1 molar ratio in 1:2 chloroform/methanol, the complex Zn^IIL(CH₃OH) was prepared. The three metal complexes and the prepared ligand were characterized by spectroscopic methods (IR, UV-vis, and NMR spectroscopy), X-ray crystallography, and DFT calculations. Electrochemically generated one-electron oxidized metal complexes [NiL]⁺, [CuL]⁺, and [ZnL(CH ₃OH)]⁺ and the metal-free ligand cation radical [H ₂L]^+• were studied by EPR/UV-vis-NIR and DFT calculations. These studies demonstrated the interaction between the metal ion and the phenoxyl radical.