Synthesis, crystal structure and catecholase activity of a Ni(II) complex derived from a tetradentate Schiff base ligand

A new nickel(II) complex [Ni(L)] (1) [H₂L = 1,1^′-(1E,1^′E)-(propane-1,3-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)dinaphthalen-2-ol] was synthesized and X-ray crystallographically characterized. 1 crystallizes in orthorhombic crystal system with Cmc21 space group. The unit cell dimensions of the crystal are a = 30.6345(4) Å, b = 8.45340(10) Å, c = 7.75180(10) Å. Structural analysis reveals a tetradentate chelation behaviour of the dianionic ligand H₂L having a distorted square planar geometry around Ni(II) with NiN₂O₂ chromophore in 1. The title complex 1 behaves as an effective catalyst towards oxidation of 3,5-ditertiarybutyl catechol (3,5-DTBC) in acetonitrile to its corresponding quinone derivative in air. The reaction follows first-order reaction kinetics with rate constant 4.28 × 10^-5 min ^-1. The reaction follows Michaelis-Menten enzymatic kinetics with a turnover number of (K _{c a t} ) 140.72 h^-1 in acetonitrile. [Figure not available: see fulltext.]