Determinative Effect of Axial Linearity on Single‐Molecule Magnet Performance in Dinuclear Dysprosium Complexes

Abstract

AbstractTwo dichloride‐bridged dinuclear dysprosium(III) complexes based on salen ligands, namely, [Dy(L1)(μ‐Cl)(thf)]2 (1; H2L1=N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)phenylenediamine) and [Dy2(L2)2(μ‐Cl)2(thf)2]2 (2; H2L2=N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)ethylenediamine) are reported. These two complexes have two short Dy−O(PhO) bonds that exhibit angles of ∼90° for 1 and ∼143° for 2, leading to clear slow relaxation of the magnetization for 2 and not for 1. Compound 2 has a near‐identical core to the recently reported compound [Dy2(L3)2(μ‐Cl)2(thf)2] (3; H2L3=N‐(2‐pyridylmethyl)‐N,N‐bis(2′‐hydroxy‐3′,5′‐di‐tert‐butylbenzyl)amine). The only substantial difference is the relative angle of the two O(PhO)−Dy−O(PhO) vectors, which is collinear in 2 owing to inversion symmetry and ∼68° in 3 due to a molecular C2 axis. It is shown that this subtle structural difference leads to large differences in the dipolar ground states, giving rise to open magnetic hysteresis for 3 and not for 2.