Synthesis, structure, magnetic and magnetocaloric properties of a series of Cr4IIILnIII complexes

The hydrothermal reaction of CrCl3 center dot 6H(2)O and Ln(NO3)(3)center dot xH(2)O in the presence of di(2-pyridil)ketone, and sodium acetate in water leads to the formation of a series of [Cr(4)Ln(CH3COO)(pyCOO)((py)(2)COO)(4)]center dot(NO3)(2)center dot nH(2)O complexes (with Ln = Gd(III), Tb(III), Dy(III), and n = 19 or 20). The four newly synthesized complexes were characterized by single crystal X-ray diffraction technique and their magnetic properties were fully investigated by dc (direct current) and ac (alternating current) magnetic susceptibility measurements. Single crystal X-ray studies revealed that the dysprosium derivative crystallizes as two different structural forms: a triclinic P (1) over bar form and a monoclinic P2(1)/n form. The gadolinium and the terbium derivatives were isostructural to the dysprosium monoclinic form. Surprisingly, full static and dynamic magnetic studies revealed that none of the synthesized complexes exhibit single molecule magnet behaviour, while the gadolinium derivative displays a magnetocaloric effect (MCE).