Ternary copper(II) Complexes of the anticonvulsant drug valproate with diimines as superoxide dismutase mimics

Abstract

Mononuclear complexes of the type [Cu(valp)z(2,2 --bpy)]H 2 0 (2), Cu(valp)2 (phen) (3), and Cu(valp)z(dmph) (4), and polynuclear complexes of the type [Cu(valp)z( µ-4,4 --bpy)]n (5), and [Cu 2 (valp)4 (µ-4,4 --bpy)Jn (6) [valp = valproate ion, bpy = bipyridine, phen = 1,10- phenanthroline, and dmph = 2,9-dimethyl-1,10- phenanthroline], were synthesized and characterized by magnetic and spectroscopic measurements. Spectral and magnetic data for complexes 2, 3, and 4 and the prelimi­nary x-ray measurements for complex 3 are consistent with mononuclear structure. The copper atom in 2 and 3 is coordinated to two nitrogen atoms from diimine, two asymmetric carboxylic oxygen atoms from each of a bidentate valproate ions to give a tertragonally elongated CuN202 + 02 chromophore. The copper atom in com­ plex 4 is coordinated to two nitrogen atoms from dmph, two carboxylic oxygens of a bidentate valproate ion, and an oxygen atom of a monodentate carboxylic group of a second valproate ion to give a very distorted square pyramid or trigonal bipyramid CuN2O3 chromophore. The preceding data for 5 and 6 indicate that these complexes are polymeric in which the nitrogen atoms of 4,4 --bpy ligands bridge mononuclear Cu(valp)2 moities, coordinating equatorially in complex 5, while bridge binuclear Cu(µ-valp)4 Cu moities, coordinating axially in complex 6. The superoxide dismutase-mimetic activity of the binary complex, Cuz(valp)4 (1), and of the previ­ous ternary complexes was measured and found to be in the order : 2 =3 > 6 > 4 > 1 > 5.