A series of salen-type asymmetric dinuclear Dy(iii) complexes: site-resolved two-step magnetic relaxation process

Abstract

A series of asymmetric dinuclear dysprosium complexes, namely, [Dy₂(L)₂(DBM)₂(H₂O)]·2CH₂Cl₂ (2), Dy₂(L)(DBM)₄(H₂O) (3), [Dy₂(L)(BTFA)₄(H₂O)]·(Et₂O) (4) and Dy₂(L)(hmac)₄(H₂O) (5) (H₂L = N,N′-bis(salicylidene)-o-phenylenediamine, DBM = dibenzoylmethane, BTFA = benzoyltrifluoroacetone and hmac = hexamethylacetylacetonate), are structurally and magnetically characterized. Complex 2 is elaborately designed by fine-tuning the local environment of one anisotropic center in a previously studied crystallographically independent {Dy2} SMM (1) displaying a separated two-step relaxation process, and consequently the one-to-one relationship between the spin sites and the relaxation processes is successfully confirmed. In addition, enhanced energy barriers were obtained among complexes 3–5 after introducing highly electron withdrawing groups on β-diketonate ligands. This work sheds light on the source of the complex multiple relaxations and provides a rational design of lanthanide SMMs with improved magnetic properties.