Modulation of the Magnetic Anisotropy via the Ligand\nField in Sandwiched Erbium Complexes

Among lanthanide-based single-molecule\nmagnets (SMMs), erbium(III)\nis a Kramers ion, apart from dysprosium(III), which provides magnetic\nbistability in the presence of a suitable coordination environment.\nHowever, Er-based SMMs exhibit significantly less magnetic anisotropy\nthan Dy because their prolate electronic density necessitates equatorially\ncorrelated ligands to minimize the charge contact with the Er atom.\nHere, in this work, we have computationally investigated the heteroleptic\norganometallic complexes with an Er(III) atom sandwiched between two\ndistinct cyclic rings (five- and eight-membered) with the aim of tuning\nthe magnetic anisotropy via exploiting the ligand field. The ligand\nfield is manipulated by substituting one of the C atoms from the five-membered\nring with heteroatoms (groups 14 and 15), while the other (eight-membered)\nring remains intact. The electronic and magnetic properties have been\ninvestigated using first-principles-based ab initio approaches. The\ndistortion in the planarity of the five-membered ring generated by\nthe larger heteroatom affects the bonding with magnetic Er and consequently\nthe electronic structure. This is observed to modify the ligand field\nand the magnetic axis, thereby improving the magnetic relaxation barrier.