Directed synthesis of {Cu₂(II)Zn₂(II)} and {Cu₈(II)Zn₈(II)} heterometallic complexes.

Two new heterometallic complexes [Cu2Zn2(H4L)2(CH3COO)2Cl2]·2.5CH3OH·0.5H2O (1) and [Cu8Zn8(OH)8(H4L)8](Cl)2(ClO4)6·16H2O (2) have been synthesised following two different preparative routes, by using the polydentate ligand Bis-tris propane (H6L = 2,2'-(propane-1,3-diyldiimino)bis[2-(hydroxymethyl)propane-1,3-diol]). Herein, we describe the synthesis, structure, and magnetic properties of 1, a tetramer which forms in the absence of base and 2, a hexadecanuclear complex with a remarkable double-concentric ring structure that forms in the presence of base. Antiferromagnetic coupling between Cu(II) ions is observed in both compounds despite the long distances between paramagnetic metal centres, due to the involvement of diamagnetic Zn(II) ions in the magnetic exchange pathway.