Two new coplanar tetranuclear lanthanide complexes (Ln = Gd(III) and Dy(III)) with magnetic refrigeration and slow magnetic relaxation behaviors

Abstract

Two novel tetranuclear Ln (III) complexes, namely [Ln4(µ3-OH)2(tmhd)4L6] (Ln(III) = Gd (1), Dy (2); HL = 5-(2-thenylidene)-8-hydroxylquinoline; tmhd = 5-(4-methylbenzylidene)-8-hydroxylquinoline), were synthesized and their structures and magnetic properties were characterized. The two complexes are both composed of one planar [Ln4(µ3-OH)2] center, in which adjacent eight-coordinated Ln(III) ions are bridged by phenoxy oxygen atoms and µ3-OH molecules. A magnetic investigation revealed that complex 1 displays cryogenic magnetic refrigeration properties with −ΔSm = 21.13 J kg−1 K−1 at T = 2.5 K and ΔH = 7.0 T. For complex 2, a slow magnetic relaxation behavior with an energy barrier of 67.8 K was observed.