A New {Dy₅} Single-Molecule Magnet Bearing the Schiff Base Ligand N-Naphthalidene-2-amino-5-chlorophenol

A new {Dy₅} cluster compound has been synthesized and structurally characterized from the initial use of the Schiff base ligand N-naphthalidene-2-amino-5-chlorophenol (nacpH₂) in coordination chemistry. The 1:1 reaction between Dy(hpd)₃∙2H₂O and nacpH₂, in a solvent mixture comprising CH₂Cl₂ and MeOH, afforded orange crystals of [Dy₅(OH)₂(hpd)₃(nacp)₅(MeOH)₅] (1) in 70% yield, where hpd⁻ is the anion of 3,5-heptadione. The {Dy₅} complex can be described as two vertical {Dy₃(μ₃-OH)}⁸⁺ triangles sharing a common vertex; such a metal topology is unprecedented in 4f-metal cluster chemistry. Direct current (dc) magnetic susceptibility studies revealed the presence of some weak ferromagnetic exchange interactions between the five Dy^III ions at low temperatures. Alternating current (ac) magnetic susceptibility measurements at zero applied dc field showed that complex 1∙3MeOH∙CH₂Cl₂ exhibits temperature- and frequency-dependent out-of-phase signals below ~20 K, characteristics of a single-molecule magnet (SMM). The resulting relaxation times were used to construct an Arrhenius-type plot and determine an effective energy barrier, U_eff, of 100 K for the magnetization reversal. The application of a small dc field of 200 Oe resulted in the surpassing of the quantum tunneling process and subsequently the increase of the U_eff to a value of 170 K. The reported results are part of a long-term program aiming at the preparation of structurally and magnetically interesting lanthanide complexes bearing various Schiff base chelating/bridging ligands. View Full-Text