New benzothiazole based copper(II) hydrazone Schiff base complexes for selective and environmentally friendly oxidation of benzylic alcohols: The importance of the bimetallic species tuned by the choice of the counterion
Aleksandra Bocian , Adam Gorczyński , Damian Marcinkowski , Samanta Witomska , Maciej Kubicki , Paulina Mech , Małgorzata Bogunia , Jakub Brzeski , Mariusz Makowski , Piotr Pawluć , Violetta Patroniak
AbstractGreen and sustainable chemistryapproaches necessitate anongoing investigation towards new, environmentallybenign and selective catalysts. We have thus prepared a new benzothiazole-scaffolded hydrazone Schiff base ligand L and coordinated it with copper(II) ions leading tofive different complexes, the form of which in the solidstate is counterion-dependent. Nitrate, chloride and triflate anions lead to monometallic species, whereas utilization of sulfates and tetrafluoroborates is responsible for the formation of bimetallic assemblies. The catalytic efficiency of synthesized compounds was shown in Cu-TEMPO (2,2,6,6-tetramethyl-l-piperidinoxyl) aerobicoxidation of activated alcohols resulting in good to excellent conversions and 100% selectivity to form the corresponding aldehydes. Considering the experimental results and Density Functional Theory calculations we propose two most plausible reaction mechanisms that further corroborate the enhanced activity of bimetallicspecies. It appears that the tridentate character of the ligand sacrifices some of the overall catalytic efficiencyfor the selectivity of the process. Aqueous reaction medium, low catalyst loading, air as oxidant and exclusive oxidative selectivity render these CuII complexes promising candidates for further improvement.
|Journal series||Journal of Molecular Liquids, ISSN 0167-7322, e-ISSN 1873-3166, (N/A 100 pkt)|
|Publication size in sheets||0.5|
|Keywords in English||copper, coordination compounds, complexes, Schiff base, hydrazone, alcohol oxidation, Density Functional Theory (DFT), green chemistry, environmental chemistry|
|ASJC Classification||; ; ; ; ;|
|Score||= 100.0, 28-02-2020, ArticleFromJournal|
|Publication indicators||: 2018 = 1.275; : 2018 = 4.561 (2) - 2018=4.136 (5)|
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