Crystal structures and magnetic properties of two series of phenoxo-O bridged dinuclear Ln2 (Ln = Gd, Tb, Dy) complexes

Six dinuclear lanthanide compounds of the formulae [Ln(2)(3m-L4)(2)(L2)(2)(MeOH)(2)]center dot 6MeOH (Ln = Gd - 1a, Tb - 1b, and Dy - 1c) and [Ln(2)(3m-L4)(2)(L2)(2)(DMF)(2)] (Ln = Gd - 2a, Tb - 2b, and Dy - 2c; DMF = N,N-dimethylformamide, H(2)3m-L4 = (2-[(E)-(3-metoxysalicylidene)amino]phenol), and HL2 = 1,3-diphenyl-1,3-diketopropane) were prepared and characterized by elemental analysis, FTIR spectroscopy, thermogravimetric measurements, single-crystal X-ray structural analysis, and magnetometry, and Gd-2 and Dy-2 compounds by ab initio methods as well. The structural analysis revealed the isostructurallity of the compounds within the series of 1-ac and 2-ac. The analysis of the variable temperature magnetic data showed the presence of a weak antiferromagnetic coupling in the Gd-2 compounds (J/cm(-1) = -0.13 for 1a and J/cm(-1) = -0.17 for 2a). The magnetocaloric effect was studied on compound 2a with the maximum value of -Delta S-M = 22.9 J kg(-1) K-1 at T = 2.0 K and B = 9 T, which is the highest value among the Gd-2 double phenoxo-bridged compounds observed up to now. Both the Dy-2 compounds (1c and 2c) exhibit slow-relaxation of magnetization in zero external static magnetic field. Magnetic anisotropy, intradimer magnetic coupling and magnetization blocking barriers were also studied by ab initio methods for 1c and 2c.