Slow magnetic relaxation in a {EuCu₅} metallacrown

A Eu III Cu 5 metallacrown displays field-induced slow magnetic relaxation, in which the Eu III with diamagnetic ground state enhances the relaxation rates. A 3d–4f heterometallic metallacrown with formula of [EuCu 5 (quinha) 5 (sal) 2 (py) 5 ]CF 3 SO 3 ·py·3H 2 O ( 1 ) (H 2 quinha = 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 5 ( 2 ) and YCu 5 ( 3 ) complexes show that the slow dynamics mainly arise from the Cu 5 S = 1/2 ground state rather than the Eu III ion. However, the Eu III ion enhances the relaxation rates of the Cu 5 unit which likely arises from second-order effects in the formally diamagnetic 7 F 0 ground state of Eu III .