Oxidation of thymol catalysed by a water-soluble Cu(II)-adipate-diphenylamine complex in a biphasic medium

A metal–organic framework involving a dicarboxylate (adipic acid) and dipyridylamine (dpya), [Cu 2 (dpya)( µ -adipate)]. 2ClO 4 ·2H 2 O, has been synthesized by one-pot reaction and structurally characterized by X-ray diffraction. Pentacoordinated Cu(II) dimer complex links the adjacent Cu(dpya) units through chelating carboxylate oxygens of adipate dianion in a coordination pattern with the metal center. The centrosymmetric adipate-bridged dinuclear complex cations [Cu 2 (dpya)( µ -adipate)] 2+ are assembled into pseudo-2D supramolecular networks through aromatic stacking interactions (4.108 Å) and also hydrogen bondings with counter ion with the coordinated water molecule. The catalytic performance of the compound was investigated for thymol (T) oxidation in organic solvents and water/hexane biphasic systems. Its selectivity was measured as 100 % for T to thymoquinone (TQ). A novel, simple, and efficient catalyst system (TOF = 400 h −1 ) was developed for the oxidation of T into a valuable derivate, TQ, using TBHP with subs./cat.(1 0 0) in a water/hexane biphasic system at 70 ο C.