From Dy-chain to Dy-dimer: Significant structural variation induced only by counter cations and slow magnetic relaxation behaviors

Abstract

Herein we report a family of Dy complexes with 1,1,1,5,5,5-hexafluoropentane-2,4‑dione (Hhfac), [Et2MeNH][Dy(hfac)3(OAc)] (1), [Et3NH][Dy(hfac)3(OAc)] (2) and [(n-Pr)3NH]2[Dy2(hfac)6(OAc)2] (3), among which a rare structural variation has been realized by the change of organic ammonium counter cations. These complexes are all constructed from mononuclear [Dy(hfac)3] building units and OAc− linkages, while employing different protonated tertiary amines as the counter cations. The Namine-H∙∙∙Oacetate hydrogen bonds, which are formed between counter cations and OAc− bridges in all complexes, make each counter cations just wedge into the gaps between adjacent [Dy(hfac)3] building units. The hfac‒ groups of each [Dy(hfac)3] unit thus inversed to other side along with the enlarging of the steric hindrance of counter cations, resulting in a significant structural variation from infinite chain topologies of 1 and 2 to discrete dimer structure of 3. For such significant structural variation induced only by the counter cations, to our knowledge, it is the first time in the whole lanthanide complex family. The magnetic studies revealed that 1–3 all show field-induced single-molecule magnets (SMMs) behavior, with the efficient energy barriers (Ueff) of 23.9, 8.5, and 11.2 K, respectively.