Cu II acetate complexes involving N,N,O donor Schiff base ligands: Mono-atomic oxygen bridged dimers and alternating chains of the dimers and Cu 2(OAc) 4

Abstract

Two tridentate N,N,O donor Schiff bases, HL 1 (4-(2-ethylamino-ethylimino)-pentan-2-one) and HL 2 (3-(2-amino-propylimino)-1-phenyl-butan-1-one) on reaction with Cu II acetate in presence of triethyl amine yielded two basal-apical, mono-atomic acetate oxygen-bridging dimeric copper(II) complexes, [Cu 2L 1 2(OAc) 2] ( 1), [Cu 2L 2 2(OAc) 2] ( 2). Whereas two other similar tridentate ligands HL 3 (4-(2-amino-propylimino)-pentane-2-one) and HL 4 (3-(2-amino-ethylimino)-1-phenyl-butan-1-one) under the same conditions produced a mixture of the corresponding dimers and a one-dimensional alternating chain of the dimer and copper acetate moiety, [Cu 4L 3 2(OAc) 6] n ( 3) and [Cu 4L 4 2(OAc) 6] n ( 4), formed by a very rare μ 3 bridging mode of the acetate ion. All four complexes ( 1– 4) have been characterized by X-ray crystallography. The isotropic Hamiltonian, H = − JS 1 S 2 has been used to interpret the magnetic data. Magnetic measurements of 1 and 2 in the temperature range 2–300 K reveal a very weak antiferromagnetic coupling for both complexes ( J = −0.56 and −1.19 cm −1 for 1 and 2, respectively).