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

Abstract

Six dinuclear lanthanide compounds of the formulae [Ln₂(3m-L4)₂(L2)₂(MeOH)₂]·6MeOH (Ln = Gd – 1a, Tb – 1b, and Dy – 1c) and [Ln₂(3m-L4)₂(L2)₂(DMF)₂] (Ln = Gd – 2a, Tb – 2b, and Dy – 2c; DMF = N,N-dimethylformamide, H₂3m-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 Gd₂ and Dy₂ compounds by ab initio methods as well. The structural analysis revealed the isostructurallity of the compounds within the series of 1a–c and 2a–c. The analysis of the variable temperature magnetic data showed the presence of a weak antiferromagnetic coupling in the Gd₂ 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 −ΔS_M = 22.9 J kg⁻¹ K⁻¹ at T = 2.0 K and B = 9 T, which is the highest value among the Gd₂ double phenoxo-bridged compounds observed up to now. Both the Dy₂ 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.