Slow magnetic relaxation in a {EuCu} metallacrown.

A 3d-4f heterometallic metallacrown with formula of [EuCu(quinha)(sal)(py)]CFSO·py·3HO (1) (Hquinha = 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 {LuCu} (2) and {YCu} (3) complexes show that the slow dynamics mainly arise from the {Cu} S = 1/2 ground state rather than the Eu ion. However, the Eu ion enhances the relaxation rates of the {Cu} unit which likely arises from second-order effects in the formally diamagnetic F ground state of Eu.