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Entrapment of a Pseudo ‐Tetrahedral Co II Center by Thioether Sulfur Bound {Co 2 ( μ ‐L)} Fragments: Synthesis, Field‐Induced Single‐Ion Magnetism and Catechol Oxidase Mimicking Activity
Author(s) -
Das Manisha,
Basak Dipmalya,
Trávníček Zdeněk,
Vančo Ján,
Ray Debashis
Publication year - 2019
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201901109
Subject(s) - thioether , chemistry , crystallography , ion , ligand (biochemistry) , ligand field theory , catechol , center (category theory) , metal , stereochemistry , analytical chemistry (journal) , inorganic chemistry , biochemistry , receptor , organic chemistry , chromatography
Simultaneous incorporation of both Co II and Co III ions within a new thioether S‐bearing phenol‐based ligand system, H 3 L (2,6‐bis‐[{2‐(2‐hydroxyethylthio)ethylimino}methyl]‐4‐methylphenol) formed [Co 5 ] aggregates [Co II Co III 4 L 2 ( μ ‐OH) 2 ( μ 1,3 ‐O 2 CCH 3 ) 2 ](ClO 4 ) 4 ⋅H 2 O ( 1 ) and [Co II Co III 4 L 2 ( μ ‐OH) 2 ( μ 1,3 ‐O 2 CC 2 H 5 ) 2 ](ClO 4 ) 4 ⋅H 2 O ( 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 U eff /k B =30 K ( 1 ) and 33 K ( 2 ), and τ 0 =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 Co II centers, thus affecting the D and U eff /k B values. Theoretical studies also support the experimental findings and reveal the origin of the anisotropy parameters. In solutions, both 1 and 2 which produce {Co III 2 ( μ ‐L)} units, display solvent‐dependent catechol oxidation behavior toward 3,5‐di‐ tert ‐butylcatechol in air. The presence of an adjacent Co III ion tends to assist the electron transfer from the substrate to the metal ion center, enhancing the catalytic oxidation rate.