Oxazolidine-Based Chloro-Bridged Dimeric Copper(II) Complex: A Bifunctional Catalyst for Enzyme-Mimetic Aerobic...

Oxazolidine-based dinuclear Cu-(II) complexes, [Cu ^II ₂ (μ ₂ -Cl) ₂ (Cl) ₂ (L _1R2S/1S2R ) ₂ ] (1 and 2), were synthesized using a chiral N,N-donor ligand ( L _1R2S/1S2R ) and CuCl₂·2H₂O. Single-crystal X-ray diffraction (SCXRD) confirmed the formation of a μ₂-Cl-bridged copper complex. Structural features of the dinuclear complexes have been examined in detail, which provides information on C-H···π and π···π supramolecular interactions. The catalytic performance was evaluated in three complementary transformations: the oxygen evolution reaction (OER), catecholase activity, and phenoxazinone synthase (PHS) activity. Electrochemical investigations provide insights into water oxidation catalysis, while spectrophotometric studies were conducted to evaluate catecholase activity toward 3,5-di-tert-butylcatechol (DTBC), and for PHS, o-aminophenol (OAPH) was used. Faradaic efficiencies (FEs) were calculated as 86 ± 6% for O₂ and 76 ± 3% for H₂ in the case of OER activity, and catalytic efficiencies (k _cat) were 1.9 ± 0.4 × 10³ and 5.5 ± 0.6 × 10³ h^-1 for catecholase- and PHS-like activities, respectively. Electrochemical, kinetic, and mechanistic studies (in the case of biomimicking activities) reveal that the ligand environment facilitates the redox cycle of Cu-(I)/Cu-(II) and supports the substrate oxidation pathway. Dinuclear copper complexes resemble the active sites of copper oxidase enzymes, and the development of such systems is important for understanding biological activity and designing oxidation catalysts. These findings provide new insights into the design of multifunctional, earth-abundant catalysts capable of energy conversion and oxidation chemistry at the same time.