Effect of Ligand Field Tuning on the SMM Behavior for Three Related Alkoxide-Bridged Dysprosium Dimers

The
synthesis and characterization of three Dy2 compounds,
[Dy2(HL1)2(NO3)4] (1), [Dy2(L2)2(NO3)4] (2), and [Dy2(HL3)2(NO3)4] (3), formed using related tripodal ligands with a central tertiary
amine bearing picolyl and alkoxy arms, 2-[(2-hydroxy-ethyl)-pyridin-2-ylmethylamino]-ethanol
(H2L1), 2-(bis-pyridin-2-ylmethylamino)-ethanol
(HL2), and 2-(bis-pyridin-2-ylmethylamino)-propane-1,3-diol
(H2L3), are reported. The compounds are rare
examples of alkoxide-bridged {Dy2} complexes and display
capped square antiprism coordination geometry around each DyIII ion. Changes in the ligand field environment around the DyIII ions brought about through variations in the ligand donors can be
gauged from the magnetic properties, with compounds 1 and 2 showing antiparallel coupling between the DyIII ions and 3 showing parallel coupling. Furthermore,
slow relaxation of the magnetization typical of SMM behavior could
be observed for compounds 2 and 3, suggesting
that small variations in the ligand field can have a significant influence
on the slow relaxation processes responsible for SMM behavior of DyIII-based systems.