Correlations between structure and magnetism of three N,N'-ethylene-bis(3-methoxysalicylideneimine) gadolinium complexes

Three Salen-like gadolinium complexes, namely, mononuclear (4f) complex [{H2L}Gd(NO3)3] (1), heterodinuclear (3d-4f) complex [{LCu}Gd(NO3)3]·0.25H2O (2) and dimeric heterotrinuclear (3d-4f-3d') complex [{LCu}Gd(H2O)3{Fe(CN)6}]2·6H2O (3) [H2L = N,N'-ethylene-bis(3-methoxysalicylideneimine)] have been synthesized by stepwise reactions. X-ray diffraction analysis reveals that 1 is of a discrete structure in which H2L coordinates to gadolinium ion through O2O2 moiety. Then, addition of Cu(Ac)2 · H20 to the mononuclear lanthanide complex yields expected heterodinuclear (3d-4f) complexes [{LCu}Gd(NO3)3]. 3 features a unique 1D ladder-like topology structure through the intermolecular double links of Cu-N bonds. The measurement of variable-temperature magnetic susceptibility reveals that complex 1 exhibits antiferromagnetic interaction while 2 and 3 exhibit ferromagnetic interaction between spin carriers. The correlations between the structure and magnetism are described and discussed.