From zero-dimensional to one-dimensional chain N-oxide bridged compounds with enhanced single-molecule magnetic performance

Abstract

A series of dinuclear dysprosium complexes bridged by pyridine-NO ligands with formula [Ln₂(BTA)₆(pyNO)₂] (1Dy, Ln = Dy, 1Y, Ln = Y and 1Gd, Ln = Gd) (BTA = benzoyltrifluoroacetone, pyNO = pyridine-N-oxide) were structurally and magnetically characterized. The X-ray crystallographic analyses of the structures revealed that the NO group serves as the effective bridge to link two Dy(III) centers and the periphery β-diketonate (BTA) ligands complete the rest of the coordination sphere. The dynamic magnetic measurements revealed that complex 1Dy displayed significant zero-field single-molecule magnetic (SMM) behaviour with 72 K energy barrier and 2.5 K hysteresis temperature. In order to extend this dinuclear system, double N-oxide bridged ligand 4,4′-bpdo(4,4′-bipyridine-N,N′-dioxide) was used, and consequently, a series of one-dimensional chain complexes possessing repeated [Ln₂(BTA)₆(pyNO)₂] units were synthesized with formula [Ln₂(BTA)₆(4,4′-bpdo)]_n·2EtOH (2Dy, Ln = Dy, 2Y, Ln = Y and 2Gd, Ln = Gd). The AC magnetic susceptibility measurements revealed that complex 2Dy exhibited significant zero-field slow magnetic relaxation behavior with a higher effective energy barrier of 87 K and a hysteresis temperature of 3 K than 1Dy albeit the separation between the repeated units is large.