title: Slow relaxation dynamics of a mononuclear Er(iii) complex surrounded by a ligand environment with anisotropic charge density.
abstract: Two sets of isostructural mononuclear compounds, [Ln(LOMe)2(H2O)2](PF6) [1, Ln = Er; 3, Ln = Gd; LOMe= CpCo{P(O)(O(CH3))2}3] and Ln(LOMe)2(NO3) (2, Ln = Er and 4, Ln = Gd), are synthesized by self-assembly of the respective lanthanide ions and tripodal chelate ligands. The Ln ions are encircled by two LOMeligands, and two water molecules or one nitrate anion. Each octacoordinated Ln center adopts a distorted square antiprism geometry. The Er complex (2) chelated by a nitrate anion shows slow dynamics in magnetic relaxation, diagnostic of a single-ion magnet. Quantum tunneling in 2 is effectively blocked by application of an external field. Weak intermolecular magnetic interactions occur in 2, and are supported by the magnetic behavior of 4. Chemical dilution of Er with the diamagnetic Y ion can nullify magnetic interactions and suppress quantum tunneling. Generation of slow relaxation dynamics in the Er system is related to the anisotropic charge distribution supplied by the coordination of ligands with different charge densities, as observed in the Dy analogue. This suggests that magnetic anisotropy arises in a coordination system when an anisotropic lanthanide ion (Dy and Er) is surrounded by a ligand environment with anisotropic charge density, resulting in slow magnetic relaxation.
authors.affiliation: Department of Chemistry, Korea University, Seoul 136-713, Korea. cshong@korea.ac.kr.
authors.forename: Kwang Soo
authors.initials: KS
authors.lastname: Lim
authors.affiliation: Department of Chemistry, Korea University, Seoul 136-713, Korea. cshong@korea.ac.kr.
authors.forename: Dong Won
authors.initials: DW
authors.lastname: Kang
authors.affiliation: Department of Chemistry, Korea University, Seoul 136-713, Korea. cshong@korea.ac.kr.
authors.forename: Jeong Hwa
authors.initials: JH
authors.lastname: Song
authors.affiliation: Department of Chemistry, Korea University, Seoul 136-713, Korea. cshong@korea.ac.kr.
authors.forename: Han Geul
authors.initials: HG
authors.lastname: Lee
authors.affiliation: Space-Time Resolved Molecular Imaging Research Team, Korea Basic Science Institute, Seoul 136-713, Korea.
authors.forename: Mino
authors.initials: M
authors.lastname: Yang
authors.affiliation: Department of Chemistry, Korea University, Seoul 136-713, Korea. cshong@korea.ac.kr.
authors.forename: Chang Seop
authors.identifier: http://orcid.org/0000-0002-4329-4745
authors.initials: CS
authors.lastname: Hong