A family of 3d metal clusters based on N-N single bonds bridged quasi-linear trinuclear cores: the Mn analogue displaying single-molecule magnet behavior.

The reactions of the diacylhydrazine ligands ,'-bisalicyl-2,6-pyridine dicarbohydrazide (Hsphz) and ,'-bis(3-methoxysalicyl)-2,6-pyridine dicarbohydrazide (Hmsphz) with various 3d metal salts, afforded a series of coordination clusters, namely, [Mn Mn(sphz)(acac)(CHOH)] (1, acac = acetylacetone anions), [Ni (msphz)(Py)] (2, Py = pyridine), [Cu (sphz)(Py)] (3) and [Cu (msphz)(Py)]·2DMF·2HO (4). Cluster 1 and 2 are single ligand assembled quasi-linear trinuclear structures. Both 3 and 4 consist a pair of quasi-linear {Cu} cores, which are linked together by two crossed ligands. The adjacent 3d metal ions in all trinuclear cores of 1-4 are bridged by N-N single bonds of ligands, which convey ferromagnetic (FM) interactions between 3d metal centers of 1, and antiferromagnetic (AFM) interactions between those of 2-4. In particular, the FM interactions and linear arrangement of mixed-valence Mn centers in 1 result in a large spin ground states value ( ) of 13/2, as well as single-molecule magnet (SMM) behavior of slow relaxation and hysteresis of magnetization.