Slow magnetic relaxation in Ni–Ln (Ln = Ce, Gd, Dy) dinuclear complexes

Three new isomorphous complexes [Ni(o-van-en)LnCl3(H2O)] [H2(o-van-en) = N,N′-ethylene-bis(3-methoxysalicylaldiminate; Ln = Ce (1), Gd (2), Dy (3)] were prepared by a stepwise reaction using mild conditions and were structurally characterised as dinuclear molecules in which Ni and Ln are coordinated by the compartmental Schiff base ligand (o-van-en)= and doubly bridged by O atoms. While the nickel(II) centre is diamagnetic within the N2O2 square-planar coordination of the Schiff base ligand, the lanthanide atoms are octa-coordinated to give an {LnCl3O5} chromophore with a fac-arrangement of the chlorido ligands. AC magnetic measurements revealed that all three complexes, including the nominally isotropic Gd(III) system, show field induced slow magnetic relaxation with two or three relaxation channels: at T = 1.9 K the low-frequency relaxation time is τLF(1) = 0.060 s at BDC = 0.5 T, τLF(2) = 0.37 s at BDC = 0.3 T, and τLF(3) = 1.29 s at BDC = 0.15 T.Financial support from Slovak grant agencies (APPV-18-0016 and VEGA 1/0063/17) is gratefully acknowledged, as is support from the Ministerio de Ciencia, Innovación y Universidades (Spain, Grants MAT2015-68200-C2-1-P and PGC2018-093451-B-I00), the European Union Regional Development Fund, FEDER), the Diputación General de Aragón, Project M4, E11_17R. Also, this work was supported by the project NFP313010V954 of call OPVaI-VA/DP/2018/1.1.3-07. AV thanks the National Scholarship Programme of the Slovak Republic and grant VVGS-PF-2018-777.The support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).Peer reviewe