Ether formation on the tridentate Schiff base ligands of copper(II) complexes

The crystal and molecular structures of three copper-containing complexes and their activities in mimicking galactose oxidase

The structures of three copper-containing complexes, namely (benzoato-κ²O,O')[(E)-2-({[2-(diethylamino)ethyl]imino}methyl)phenolato-κ³N,N',O]copper(II) dihydrate, [Cu(C₇H₅O₂)(C₁₃H₁₉N₂O)]·2H₂O, 1, [(E)-2-({[2-(diethylamino)ethyl]imino}methyl)phenolato-κ³N,N',O](2-phenylacetato-κ²O,O')copper(II), [Cu(C₈H₇O₂)(C₁₃H₁₉N₂O)], 2, and bis[μ-(E)-2-({[3-(diethylamino)propyl]imino}methyl)phenolato]-κ⁴N,N',O:O;κ⁴O:N,N',O-(μ-2-methylbenzoato-κ²O:O')copper(II) perchlorate, [Cu₂(C₈H₇O₂)(C₁₂H₁₇N₂O)₂]ClO₄, 3, have been reported and all have been tested for their activity in the oxidation of D-galactose. The results suggest that, unlike the enzyme galactose oxidase, due to the precipitation of Cu₂O, this reaction is not catalytic as would have been expected. The structures of 1 and 2 are monomeric, while 3 consists of a dimeric cation and a perchlorate anion [which is disordered over two orientations, with occupancies of 0.64 (4) and 0.36 (4)]. In all three structures, the central Cu atom is five-coordinated in a distorted square-pyramidal arrangment (τ parameter of 0.0932 for 1, 0.0888 for 2, and 0.142 and 0.248 for the two Cu centers in 3). In each species, the environment about the Cu atom is such that the vacant sixth position is open, with very little steric crowding.