Slow magnetic relaxation in a {EuCu₅} metallacrown

Abstract

A 3d-4f heterometallic metallacrown with formula of [EuCu₅(quinha)₅(sal)₂(py)₅]CF₃SO₃·py·3H₂O (1) (H₂quinha = quinaldichydroxamic acid; Hsal = salicylaldehyde) has been synthesized. This complex shows field-induced slow magnetic relaxation via a Raman-like process, where studies of the isostructural {LuCu₅} (2) and {YCu₅} (3) complexes show that the slow dynamics mainly arise from the {Cu₅} S = 1/2 ground state rather than the Eu^III ion. However, the Eu^III ion enhances the relaxation rates of the {Cu₅} unit which likely arises from second-order effects in the formally diamagnetic ⁷F₀ ground state of Eu^III.