Structural and Magnetic Characterization of Two Tetranuclear Cu(II) Complexes with Closed-Cubane-Like Core Framework

Two novel tetranuclear closed-cubane like core framework complexes [Cu4(L1)4] c53(H2O) (1) and [Cu4(H2L2)4(H2O)4] (2) (H2L1=(E)-2-((1-hydroxybutan-2-ylimino)methyl)phenol; H4L2=2-((2-hydroxy-3-methoxybenzylidene)amino)-2-hydroxymethylpropane-1,3-diol) were synthesized and structurally characterized. Magnetic susceptibility measurements indicate an overall weak antiferromagnetic exchange coupling in 1, while ferromagnetic exchange coupling in 2. In agreement with their closed-cubane structure, the magnetic behavior of the two complexes have been studied by employing the isotropic spin Hamiltonian of type H=J1 (S1S3 + S1S4 + S2S3 + S2S4) - J2 (S1S2 + S3S4) (J1 describes the magnetic exchange coupling between the four Cu(II) pairs with short Cu c5 c5 c5Cu distances, while J2 characterizes the magnetic exchange coupling between the remaining two intermetallic pairs with long distances). The PHI program was used to study their magnetic behavior. A good agreement between the experimental and fitted curves was found with the following parameters: g=2.14, J1=-20.3\u2005cm 121 and J2=0\u2005cm 121 for 1 and g=2.10, J1=101.1\u2005cm 121 and J2=-51.5\u2005cm 121 for 2