Synthesis, structures, and catalytic studies of new copper(II) complexes with arene-linked pyrazolyl methane ligands

Abstract

<div><p>Two new copper complexes, [Cu₂(L1)(dipic)₂(H₂O)₂]⋅2H₂O (<b>1</b>) and [Cu₂(L2)(dipic)₂(H₂O)₂]⋅3H₂O (<b>2</b>) (L1 = 1,4-bis((1<i>H</i>-pyrazol-1-yl)methyl)benzene; L2 = 1,4-bis((3,5-dimethyl-1<i>H</i>-pyrazol-1-yl)methyl)benzene; and H₂dipic = 2,6-pyridinedicarboxylic acid), were synthesized by the reaction of copper salt, arene-linked pyrazolyl methane ligands, and 2,6-pyridinedicarboxylic acid in 95% C₂H₅OH. They were characterized by elemental analysis, IR, UV–vis, single-crystal X-ray diffraction analysis, X-ray powder diffraction, and thermogravimetric analysis. We explored the application of the copper complexes in bromination reactions; the complexes exhibited bromination catalytic activity in single-pot reaction for the conversion of phenol red into bromophenol blue. A feasible bromination reaction mechanism of copper complexes was proposed.</p></div