End-to-end azides as bridging ligands in lanthanide coordination chemistry: Magnetic and magnetocaloric properties of tetranuclear Ln(4) (Ln = Gd, Dy) complexes exhibiting a rare rhombus topology
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2018 The syntheses and magnetic properties of two new isostructural tetranuclear lanthanide complexes, [Ln4(N3)4(Tpz)8] (Ln = GdIII (1), DyIII (2) and, Tpz = tris(pyrazolyl)borate) are reported. In these complexes the lanthanide ions are eight coordinate with distorted geometries and are bridged by end-to-end azido ligands in a rare rhombus topology. Direct current magnetic susceptibility studies revealed the presence of weak ferromagnetic exchange interactions between the metal ions which were quantified in the case of the isotropic Gd4 analog to give J = 0.0080(2) cm1 and g = 2.01(1). Complex 2 exhibits frequency and temperature dependent out-of-phase () ac magnetic susceptibility signals under a 0.1 T applied field, suggestive of SMM behavior. Low temperature magnetization studies revealed that compound 1 exhibits an appreciable magnetic entropy change, Sm, which reaches a value of 20.9 J kg1 K1 at T = 3 K for H = 7 T. Theoretical calculations further support the experimental results.
