Catechol oxidase mimetic activity of copper(I) complexes of 3, 5-dimethyl pyrazole derivatives: Coordination behavior, X-ray crystallography and electrochemical study. (27th July 2016)

• Record Type: Journal Article
• Authors: Santra, Ananyakumari; Mondal, Gopinath; Acharjya, Moumita; Bera, Pradip; Panja, Anangamohan; Mandal, Tarun K.; Mitra, Partha; Bera, Pulakesh
• Is Part Of: Polyhedron. Volume 113(2016)
• Page Start: 5
• Page End: 15
• Publication Date: 2016-07-27
• Subjects: Copper(I) pyrazolyl complex -- Catecholase activity -- X-ray Crystallography -- DFT -- Cyclovoltammetry; Chemistry, Inorganic -- Periodicals; Chimie inorganique -- Périodiques; Organometaalverbindingen; Anorganische chemie; 546.05
• DOI: 10.1016/j.poly.2016.03.055
• Languages: English
• ISSNs: 0277-5387

Abstract

Graphical abstract: Isostructural copper(I) complexes of methyl-3, 5-dimethyl pyrazole-1-dithioate (L 1 ) and benzyl-3, 5-dimethyl-pyrazole-1-dithioate (L 2 ) were synthesized. The same ligands formed tetrahedral Zn(dmpz)2 Cl2 and a helical 1-D polymeric chain, [Cd(dmpz)2 Cl2 ] n following dissociation of the parent ligand into 3, 5-dimethyl pyrazole (dmpz). The copper (I) (d 10 system) analogues exhibited mimetic catecholase oxidase activity. Abstract: N 1 -substituted 3, 5-dimethylpyrazole (dmpz) namely, methyl-3, 5-dimethyl pyrazole-1-dithioate (L 1 ) and benzyl-3, 5-dimethyl-pyrazole-1-dithioate (L 2 ) were reacted with zinc(II), copper(II) and cadmium(II) chloride to study their coordination behavior. Ligands L 1 and L 2 produced isostructural complexes with composition [Cu I (L 1 )2 ][Cu I Cl2 ] (1 ) and [Cu I (L 2 )2 ][Cu I Cl2 ] (2 ), respectively when reacted with CuCl2 ·2H2 O. Copper (I) (d 10 system) analogues, 1 and2, exhibit prominent catechol oxidase activity in which a nice correlation-the easily oxidizable copper(I) center favoring the oxidation of 3, 5-DTBC (3, 5-ditertiary butyl catechol) is observed. Most importantly, these two compounds represent the class of copper(I) compounds that are rarely employed for the study of catecholase activity. The kinetics study exhibits a deuterium kinetic isotope effect in the catalytic oxidation of 3, 5-DTBC by O2 as evidenced by about 1.9 times rate retardation in the deuterated solvent, suggesting the hydrogen atom transfer in the rate-determining step from the substrate hydroxy group to the metal-bound superoxo species. With other d 10 cations, zinc(II) and cadmium(II) the ligand L 1 and/or L 2 undergoes dissociation into parent pyrazole unit i.e., 3, 5-dimethylpyrazole (dmpz) during formation of a monomeric tetrahedral Zn(dmpz)2 Cl2 (3 ) complex and a helical 1-D polymeric chain, [Cd(dmpz)2 Cl2 ] n (4 ). The possible role of intramolecular hydrogen-bonding induced helicity has been explored in4 .