Synthesis, structure and magnetism of three cubane Cu(II) and Ni(II) complexes based on flexible Schiff-base ligands

Three cubane Ni(II) and Cu(II) complexes, namely [Cu4L14]·CH3CN (1), [Ni4L14(CH3OH)4]·4H2O (2), [Ni4L24(CH3OH)4]·6H2O (3), have been synthesized from flexible polydentate Schiff bases (H2L1 and H2L2) based on o-vanillin. X-ray single-crystal analyses reveal that all three complexes own a cubane-like core M4O4 in which Cu ions in 1 are five-coordinated and Ni ions in 2 and 3 are six-coordinated. Variable-temperature magnetic susceptibility data display dominant ferromagnetic interactions in complexes 1–3 while antiferromagnetic and ferromagnetic couplings coexist in the cubane core, thus resulting in a nonzero spin ground state. The magnitude of the exchange coupling constants correlates with the geometrical parameters arising from the minor ligand modifications.

Graphical abstractThree cubane Cu(II) and Ni(II) complexes have been synthesized based on multidentate Schiff bases. Magnetic data analyses reveal that all cubic clusters display dominant ferromagnetic interactions. The results show a crucial role of the minor ligand modifications in the structural control.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Three cubane Cu(II) and Ni(II) complexes have been synthesized based on multidentate Schiff bases. ► Magnetic data analyses reveal that all cubic clusters display dominant ferromagnetic interactions. ► The results show a crucial role of the minor ligand modifications in the structural control.