An unprecedented solid of coper(II) complexes [Cu(dpa)₂NCS]₂[Cu(dpa)₂(NCS)₂](ClO₄)₂ (1) [dpa = 2,2'-dipyridylamine; SCN = thiocyanate], has been synthesized and crystallographically characterized with the aim to study the catecholase activity. The Cu(II) complex mimics the full catalytic cycle of the active site of catechol oxidase enzyme in acetonitrile medium with a turnover number of 4.788 × 10³ h⁻¹ along with the production of semiquinone radical and hydrogen peroxide. In situ generation of Cu(I) species in the catalytic pathway of catechol oxidation was established by electrochemical study and further confirmed by electron paramagnetic resonance (EPR) spectroscopy.

In this work, we have synthesised and crystallographically characterized a mononuclear iron(II) complex, [Fe(phen)₃](NO₃)₂ ·2H₂O (1) (phen = 1,10-phenanthroline). Single crystal X-ray diffraction (SXRD) analysis revealed that 1 crystallizes in monoclinic system with P 1⁻ space group. The lattice water molecules in 1 form a water-nitrate cluster, (H₂O)₂... (NO₃)₂ through strong H-bonding interaction mediated via iron(II) complex in a unique binding motif and provide additional stability to the compound in the solid state. This iron(II)complex is able to catalyze the cleavage of aromatic C-C linkage of 2,5-dihydroxybenzoic acid (Gentisic acid, GA) in oxygen environment. The iron(II) complex in the presence of two equivalent of triethylamine (Et₃N) binds with GA stoichiometrically in acetonitrile medium at 25^◦ C. Observation of GA-to-iron LMCT optical bands at 521 and 609 nm supports in situ generated iron-GA adduct in solution. This in situ generated iron-GA adduct reacts with molecular oxygen at the rate, k_obs = 6.58×10⁻³ min⁻¹ in acetonitrile and affords exclusively 2-oxo-4-hydroxy-hepta-3,5-dienedioic acid. The incorporation of both the oxygen atoms of molecular oxygen in the bio-mimicking activity of gentisate-1,2-dioxygenase by this iron(II)-phenanthroline complex remain arare example in scientific literature.