Magnetostructural correlation in tetracopper(II) cubanes

The tetradendate Schiff base ligand N-2-hydroxy-3-methoxybenzaldehyde-α-amino-iso-butyrate (H23-MeOSAIB) has been complexed with copper(II) giving rise to a tetranuclear complex [Cu4(3-MeOSAIB)4]·H2O with cubane structure classified, according to the number of Cu⋯Cu contacts and bridging angles Cu–O–Cu, as 4+2 (type II) cubane. Magnetic data is reconstructed with two exchange coupling constants. The open angle Cu1–O1–Cu2 (α = 114°) existing four times facilitates a strong antiferromagnetic coupling that is in competition with ferromagnetic interactions through the path Cu1–O2–Cu2 (α∗ = 88°) occurring four times; the resulting coupling constant is J4/hc = −80.5 cm−1 (4×). The second exchange coupling constant occurring twice is J2/hc = +6.2 cm−1 (2×) as a result of weak ferromagnetic interaction via bridges Cu1–O1–Cu1 and Cu2–O2–Cu2 (β1 = 92 and β2 = 94°). The analysis of available experimental data reveals a transparent magnetostructural correlation of J2 versus β (mean value), according to a straight line with negative slope; J4 weakly correlates with the angle α. A deep chemometric analysis has been applied in order to unhide latent magnetostructural correlations.

Tetranuclear copper(II) complex with Schiff base ligand possessing the cubane-like structure with {Cu4O4} core been studied by means of X-ray crystallography and magnetometry. The magnetic data confirm that both, the antiferromagnetic and ferromagnetic exchange coupling apply according to two coupling constants. The overall exchange coupling is of an antiferromagnetic nature.Figure optionsDownload as PowerPoint slide