Comparison of mononuclear and dinuclear copper(ii) biomimetic complexes: spectroelectrochemical mechanistic study of their catalytic pathways. Issue 36 (24th August 2022)

• Record Type: Journal Article
• Authors: Sýs, Milan; Kocábová, Jana; Klikarová, Jitka; Novák, Miroslav; Jirásko, Robert; Obluková, Michaela; Mikysek, Tomáš; Sokolová, Romana
• Is Part Of: Dalton transactions. Volume 51:Issue 36(2022)
• Page Start: 13703
• Page End: 13715
• Publication Date: 2022-08-24
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d2dt01610a
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The catecholase-like biomimetic catalysts were proved for their catechol oxidation catalytic activity in the presence of oxygen and the catalytic mechanism was proposed using voltammetry, in situ UV-Vis spectroelectrochemistry and calculations. Abstract : Two catecholase-like biomimetic catalysts, namely, two dinuclear copper complexes [Cu2 (L1)(OH)(H2 O)(EtOH)][ClO4 ]2 (C1 ) and [Cu2 Ac2 O(L1)ClO4 ] (C2 ) with the 2, 6-bis(4-methyl piperazin-1-yl-methyl)-4-formyl-phenoxy ligand (L1) together with the mononuclear complex Cu(ClO4 )2 (L2) (C3 ) containing ligand 1, 2-(C5 H4 N-6-OCH3 -2-CHN)2 CH2 CH2 (L2), were synthesized. Their catalytic pathways were investigated and compared. The evaluation of the catalytic activity of compound C1 (and C2, C3 ) using the Michaelis–Menten model was represented by values of K M = 272.93 (223.02; 1616) μmol L −1 and V max of 0.981 (1.617; 1.689) μmol L −1 s −1 . The role of water content in the solvent is also discussed. The dinuclear complexes C1 and C2 were found to be more efficient catalysts than mononuclear complex C3 . The mode of catalytic action was characterized via cyclic voltammetry, spectrophotometry, and UV-Vis spectroelectrochemistry. The catalytic mechanism of 3, 5-di- tert butyl catechol oxidation in the presence of oxygen was proposed. The reaction circle was proved by the confirmation of the chemical reversibility of complex reduction. The advantage of the in situ spectroelectrochemical measurement enabled to control the reduction of quinone formed by the chemical reaction of catechol with oxygen in solution. At this step, the simultaneous change in the absorption spectrum indicated a change in the copper redox state of the catalyst.