The reaction of a Schiff-base ligand (LH3) with lanthanide salts, pivalic acid and triethylamine in 1: 1: 1: 3 and 4: 5: 8: 20 stoichiometric ratios results in the formation of decanuclear Ln10 [Ln= Dy (1), Tb (2) and Gd (3)] and pentanuclear Ln5 complexes [Ln= Gd (4), Tb (5) and Dy (6)] respectively. The formation of Ln10 and Ln5 complexes are fully governed by the stoichiometry of the reagents used. Detailed magnetic studies on these complexes (1-6) have been carried out. Complex 1 shows a SMM behavior with an effective energy barrier for the reversal of the magnetization (Ueff)= 16.12 (8) K and relaxation time (τo)= 3.3 x 10-5 s under 4000 Oe dc field. Complex 6 shows the frequency dependent maxima in the out-of-phase signal under zero dc field, without achieving maxima above 2K. Complexes 3 and 4 show a large magnetocaloric effect with the following characteristic values:− ΔSm= 26.6 J kg-1 K-1 at T= 2.2 K for 3 and− ΔSm= 27.1 J kg-1 K-1 at T= 2.4 Kfor 4, both for an applied field change of 7 T.
16 Nov 2015
Volume: 21 Issue: 47 Pages: 16955-16967
Chemistry-A European Journal