Heterometallic [Ln(hfac)3Cu(acac)2] complexes with late 4f ions

Heterometallic [Ln(hfac)3Cu(acac)2] complexes (Ln = Eu 1, Dy 2, Er 3) can be prepared along the f-transition series. X-rays diffraction studies on well-shaped single crystals revealed for 1 - 3 a dinuclear structure. No ligand scrambling occurred, a Lewis acid-base interaction has been observed with the two metals bridged through two oxygen atoms of the acetylacetonato ligands and an oxygen atom of a hexafluoroacetylacetonato ligand. Compounds 2 and 3 can be obtained only in anhydrous conditions. (1) can be sublimed under reduced pressure, and crystals of the sublimed product, 1a, showed a polymorph structure with the same molecular identity. Magnetic studies have been carried out on 2, displaying an antiferromagnetic interaction and a field-induced slow relaxing magnetic moment with a significant phonon bottleneck effect. Compound 3, on the other hand, did not present any magnetization dynamics, with or without applied field. Quantum mechanical calculations rationalize the variation of the bond strengths from the reagents to the heterometallic complexes and quantify the Ln and Cu direct interaction, which is relevant, especially for 2.