Copper(II) tetrazolato complexes: Role in oxidation catalysis and protein binding

Abstract

Three new coordination complexes [Cu2(phen)2(ptz)4] (1), [Cu(phen)(pmtz)2] (2) and [Cu(phen)(pytz)2] (3) (ptz=5-phenyltetrazolate, pmtz=5-(2-pyrimidyl)tetrazolate and pytz=5-(2-pyridyl)tetrazolate) have been synthesized using metal mediated [2+3] cycloaddition reaction between copper bound azide polymer and different organonitriles. All complexes have been structurally characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Complex 1 shows a dinuclear structure via bridging ptz, while 2 and 3 reveal mononuclear structures. These complexes were explored as homogeneous catalysts for the selective peroxidative (with tBuOOH) oxidation of cyclohexane to cyclohexanol and cyclohexanone (KA oil) under very mild and green (solvent- and additive-free) conditions using microwave irradiation. The catecholase-like activity of the synthesized Cu(II) complexes was investigated by employing 3,5-di-tert-butylcatechol (DTBC) as a convenient model substrate, which showed first order kinetics with respect to the substrate in the oxidation of 3,5-di-tert-butyl catechol (DTBC) to 3,5-di-tert-butyl benzoquinone (DTBQ). Further, the interaction of synthesized Cu(II)-tetrazolato complexes with bovine serum albumin (BSA) was studied experimentally as well as through molecular docking to obtain detailed binding information of the Cu(II) complexes with BSA, which revealed higher binding of complex 1 than 2 and 3.