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 [Cu 4 (L 1 ) 4 ]⋅3(H 2 O) ( 1 ) and [Cu 4 (H 2 L 2 ) 4 (H 2 O) 4 ] ( 2 ) (H 2 L 1 =(E)‐2‐((1‐hydroxybutan‐2‐ylimino)methyl)phenol; H 4 L 2 =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 = J 1 ( S 1 S 3 + S 1 S 4 + S 2 S 3 + S 2 S 4 ) ‐ J 2 ( S 1 S 2 + S 3 S 4 ) ( J 1 describes the magnetic exchange coupling between the four Cu(II) pairs with short Cu⋅⋅⋅Cu distances, while J 2 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, J 1 =‐20.3 cm −1 and J 2 =0 cm −1 for 1 and g =2.10, J 1 =101.1 cm −1 and J 2 =‐51.5 cm −1 for 2 .