Biomolecular interaction, catecholase like activity and alkane oxidation in ionic liquids of a phenylcarbohydrazone-based monocopper(II) complex

A phenylcarbohydrazone-based Schiff base type ligand (E)-N′-(2-hydroxy-5-methylbenzylidene)benzohydrazide (HL) and its monocopper(II) complex [CuL(NO3)(H2O)]·(H2O) (CuL) are synthesized and structurally characterized including single-crystal X-ray crystallography. The DNA interacting efficacy of the synthesized CuL with CT (calf thymus) DNA has been investigated using different spectral and viscosity measurements. The DNA binding constant (Kb = 2.1 (±1.11) × 105 M−1) and binding site size (s = 0.31), viscosity data together with circular dichroism studies, revealed that the CuL could interact with DNA via intercalation. The protein binding ability of CuL with BSA (Bovine Serum Albumin) was investigated by absorption, fluorescence and synchronous fluorescence methods and a static quenching mechanism was observed for their interaction with BSA. CuL acts as an efficient catalyst for the aerobic oxidation of catechols (4-methylcatechol, 3,5-ditertiarybutylcatechol, 3-methoxycatechol and 3-nitrocatechol) to the corresponding quinones, in methanol/0.02 M HEPES medium at pH = 8.0 and at 25 °C. The highest activity is observed for the substituted catechol with the electron donor tert-butyl group, resulting in a turnover frequency (TOF) value of 1.45 × 104 h−1. CuL also mimics the action of other copper enzymes, being capable of catalyzing the peroxidative oxidation of cyclohexane, under in mild conditions and in several media. The best results were obtained in an ionic liquid, with a TOF of 1220 h−1.