Abstract
A series of six seven-coordinate pentagonal-bipyramidal (PBP) erbium complexes, with acyclic pentadentate [N(3)O(2)] Schiff-base ligands, 2,6-diacetylpyridine bis-(4-methoxybenzoylhydrazone) [H(2)DAPMBH], or 2,6-diacethylpyridine bis(salicylhydrazone) [H(4)DAPS], and various apical ligands in different charge states were synthesized: [Er(DAPMBH)(C(2)H(5)OH)Cl] (1); [Er(DAPMBH)(H(2)O)Cl]·2C(2)H(5)OH (2); [Er(DAPMBH)(CH(3)OH)Cl] (3); [Er(DAPMBH)(CH(3)OH)(N(3))] (4); [(Et(3)H)N](+)[Er(H(2)DAPS)Cl(2)](-) (5); and [(Et(3)H)N](+)[Y(0).(95)Er(0).(05)(H(2)DAPS)Cl(2)](-) (6). The physicochemical properties, crystal structures, and the DC and AC magnetic properties of 1-6 were studied. The AC magnetic measurements revealed that most of Compounds 1-6 are field-induced single-molecule magnets, with estimated magnetization energy barriers, U(eff) ≈ 16-28 K. The experimental study of the magnetic properties was complemented by theoretical analysis based on ab initio and crystal field calculations. An experimental and theoretical study of the magnetism of 1-6 shows the subtle impact of the type and charge state of the axial ligands on the SMM properties of these complexes.