Entrapment of a Pseudo‐Tetrahedral CoII Center by Thioether Sulfur Bound {Co2(μ‐L)} Fragments: Synthesis,Field‐Induced Single‐Ion Magnetism and Catechol Oxidase Mimicking Activity |
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| Authors: | Manisha Das Dipmalya Basak Prof Dr Zdeněk Trávníček Dr Ján Vančo Prof Dr Debashis Ray |
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| Institution: | 1. Department of Chemistry, Indian Institute of Technology, Kharagpur, 721 302 India;2. Division of Biologically Active Complexes and Molecular Magnets, Faculty of Science, Palacky University, ?lechtitel? 27, 783 71 Olomouc, Czech Republic |
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| Abstract: | Simultaneous incorporation of both CoII and CoIII ions within a new thioether S‐bearing phenol‐based ligand system, H3L (2,6‐bis‐{2‐(2‐hydroxyethylthio)ethylimino}methyl]‐4‐methylphenol) formed Co5] aggregates CoIICoIII4L2(μ‐OH)2(μ1,3‐O2CCH3)2](ClO4)4?H2O ( 1 ) and CoIICoIII4L2(μ‐OH)2(μ1,3‐O2CC2H5)2](ClO4)4?H2O ( 2 ). The magnetic studies revealed axial zero‐field splitting (ZFS) parameter, D/hc=?23.6 and ?24.3 cm?1, and E/D=0.03 and 0.00, respectively for 1 and 2 . Dynamic magnetic data confirmed the complexes as SIMs with Ueff/kB=30 K ( 1 ) and 33 K ( 2 ), and τ0=9.1×10?8 s ( 1 ), and 4.3×10?8 s ( 2 ). The larger atomic radius of S compared to N gave rise to less variation in the distortion of tetrahedral geometry around central CoII centers, thus affecting the D and Ueff/kB values. Theoretical studies also support the experimental findings and reveal the origin of the anisotropy parameters. In solutions, both 1 and 2 which produce {CoIII2(μ‐L)} units, display solvent‐dependent catechol oxidation behavior toward 3,5‐di‐tert‐butylcatechol in air. The presence of an adjacent CoIII ion tends to assist the electron transfer from the substrate to the metal ion center, enhancing the catalytic oxidation rate. |
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| Keywords: | catecholase activity cobalt magnetic anisotropy single-molecule magnets thioether ligand |
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