Synthesis, Structural Features and Physical Properties of a Family of Triply Bridged Dinuclear 3d-4f Complexes

New dinuclear M-II-Ln(III) complexes of general formulas [Cu(mu-L)(mu-OAc)Ln(NO3)(2)]center dot CH3CN center dot H2O (Ln(III) = Gd (1), Tb (2), Dy (3) and Er (4)), [Ni(CH3CN)(mu-L)(mu-OAc)Ln(NO3)(2)]center dot CH3CN (Ln(III) = Nd (5), Gd (6), Tb (7), Dy (8), Er (9) and Y (10)) and [Co(CH3CN)(mu-L)(mu-OAc)Ln(NO3)(2)]center dot CH3CN (Ln(III) = Gd (11), Tb (12), Dy (13), Er (14) and Y (15)) were prepared from the compartmental ligand N,N '-dimethyl-N,N '-bis(2-hydroxy-3-formyl-5-bromo-benzyl)ethylenediamine (H2L). In all these complexes, the transition metal ions occupy the internal N2O2 coordination site of the ligand, whereas the Ln(III) ions lie in the O-4 external site. Both metallic ions are connected by an acetate bridge, giving rise to triple mixed diphenoxido/acetate bridged M(II)Ln(III) compounds. Direct current (dc) magnetic measurements allow the study of the magnetic exchange interactions between the 3d and 4f metal ions, which is supported by density functional theory (DFT) theoretical calculations for the Gd-III-based counterparts. Due to the weak ferromagnetic exchange coupling constants obtained both experimentally and theoretically, the magneto-thermal properties of the less anisotropic systems (compounds 1 and 6) are also studied. Alternating current (ac)magnetic measurements reveal the occurrence of slight frequency dependency of the out-of-phase signal for complexes 8, 9 and 13, while complex 15 displays well-defined maximums below similar to 6 K.

Automated summary

This study presents a series of new dinuclear M-II-Ln(III) complexes prepared from a specific ligand, exhibiting complex electronic structures and magnetic properties. The magnetic exchange interactions between the metal ions and magneto-thermal properties of the complexes are investigated, shedding light on the understanding of their magnetic behavior.