Syntheses, Structures and Magnetism of Trinuclear Bimetallic MnIILnIIIMnII Complexes (Ln = La, Nd, Sm, Gd, Dy and Er) with 2,6-Dipicolinoylbis(N,N-Diethylthiourea)

Abstract

Self-assembled reactions of 2,6-dipicolinoylbis(N,N-diethylthiourea) (H₂L) with Mn(CH₃COO)₂ ⋅ 4H₂O and LnCl₃, where Ln = La, Nd, Sm, Gd, Dy, Er in MeOH lead to formation of stable trinuclear complexes of the composition [LnMn₂(L)₂(μ_1,3-CH₃COO)₂X] (Mn^IILn^IIIMn^II), where X⁻ can be κ²-CH₃COO⁻ or κ¹-CH₃COO⁻. Single crystal X-ray studies reveal their symmetric structures comprising one central Ln(III) ion, two terminal Mn(II) ions sandwiched by two doubly deprotonated ligands {L²⁻}. The magnetic properties of Mn^IILa^IIIMn^II and Mn^IIGd^IIIMn^II complexes are successfully simulated using symmetrical magnetic interaction models, giving the best fitted parameters: J_Mn-Mn=−0.120(1) cm⁻¹, g_Mn=1.99(1), TIP=4.45(7) ⋅ 10⁻⁴ cm³ mol⁻¹ K for Mn^IILa^IIIMn^II and J_Gd-Mn=0.042(1) cm⁻¹, J_Mn-Mn=−0.076(1) cm⁻¹, g_Mn=1.96(1), g_Gd=2.01(1) and TIP=3.59(14) ⋅ 10⁻⁴ cm³ mol⁻¹ K for Mn^IIGd^IIIMn^II complex. The magnetic interactions between the Mn(II) and Ln(III) ions in the other Mn^IILn^IIIMn^II complexes are studied by comparing their χ_M values to the sum of χ_M values of the Mn^IILa^IIIMn^II and the analogous Zn^IILn^IIIZn^II complexes. The Mn^IIEr^IIIMn^II complex reveals a strong ferromagnetic interaction, while the Sm, Nd, Gd and Dy complexes show weak ferromagnetic interactions.