The first exploration of coordination chemistry using a methyl substituted o-vanillin based ligand: an example starting with Dy4/Zn2Dy2 systems displaying slow relaxation of magnetization

Abstract

The literature has witnessed the exceptionally rich coordination chemistry, ranging from monomeric species to coordination polymers, generated by the Schiff base ligands derived from o-vanillin. Plenty of purely 4f and mixed 3d–4f single-molecule magnets (SMMs) have been synthesized using these ligands aiming at their several futuristic applications ranging from data storage devices to the basic unit of quantum computers. In the present endeavour, we introduced for the first time a new methyl derivative of o-vanillin, 2-hydroxy-3-methoxy-5-methylbenzaldehyde (Me-val), to explore its coordination ability as well as the electronic effect of the methyl substitution at the para position with respect to the phenolic-OH group in the resulting complexes. Consequently, a Dy₄ (1) and a Zn₂Dy₂ (2) complex have been synthesized and structurally characterized from a ligand, (E)-2-[(2-hydroxyphenyl)iminomethyl]-6-methoxy-4-methylphenol (H₂L), derived from Schiff base condensation reaction of Me-val and o-aminophenol. Both complexes are butterfly-shaped structures with varied geometries around the Dy(III) ions, and in 2, the Zn(II) centres occupy the body positions and the Dy(III) ions are in the wing positions. Magnetic studies reveal that complex 1 displays slow magnetic relaxation at zero dc field, while complex 2 exhibits field supported slow magnetic relaxation. Ab initio calculations were further performed to understand the magnetic behaviours in these complexes, which revealed that the counter complementary effect of the ferromagnetic dipole–dipole interaction and the intramolecular antiferromagnetic interaction among the Dy centres overall describe the slow magnetic relaxation behaviours in these complexes.