Mixed-ligand CuII complexes with Me5dien and heterocyclic acids. Synthesis, antioxidant and anti-inflammatory activity. Crystal structure of [Cu(Me5dien)(tpaa)(H2O)](ClO4)

The reaction of sodium salt of 2-thiophenecarboxylic acid (tpca), 2-thiopheneacetic acid (tpaa), 2-furoic acid (fa) and picolinic acid (pica), with [Cu(Me5dien)(ClO4)2] (1) (Me5dien = N, N, N′, N″ N″-pentamethyldiethylenetriamine) in a 1:1 molar ratio, afforded new mixed-ligand compounds of the type [Cu(Me5dien)(tpca)(H2O)](ClO4) (2), [Cu(Me5dien)(tpaa)(H2O)](ClO4) (3), [Cu(Me5dien)(fa)](BPh4) (4) and [Cu(Me5dien)(pica)](ClO4) (5). The new mixed-ligand complexes are mononuclear, paramagnetic, conductive compounds with a distorted square pyramidal geometry. The square pyramidal stereochemistry proposed by spectroscopic (IR, UV–vis) data was further confirmed by the X-ray structure analysis of the compound (3) in which the Cu atom is coordinated by the three N atoms from the Me5dien ligand, one O atom from the mono-carboxylate anion, lying on the equatorial square plane, and one O atom from the water molecule, occupying the axial position. The two CuO bond distances are 1.955(2) and 2.212(2) Ǻ, respectively. The complexes were tested for antioxidant/anti-inflammatory activity. Complex 4 is the most active against soybean lipoxygenase with IC50 = 100 μM. The presence of a furoic ring leads to higher lipoxygenase inhibition, whereas the picolinyl-ring supports scavenging activity.