title: Exchange coupling and magnetic anisotropy in a family of bipyrimidyl radical-bridged dilanthanide complexes: density functional theory and ab initio calculations.
abstract: The origin of the magnetic anisotropy energy barriers in a series of bpym(-) (bpym = 2,2'-bipyrimidine) radical-bridged dilanthanide complexes [(Cp*2Ln)2(μ-bpym)](+) [Cp* = pentamethylcyclopentadienyl; Ln = Gd(III) (1), Tb(III) (2), Dy(III) (3), Ho(III) (4), Er(III) (5)] has been explored using density functional theory (DFT) and ab initio methods. DFT calculations show that the exchange coupling between the two lanthanide ions for each complex is very weak, but the antiferromagnetic Ln-bpym(-) couplings are strong. Ab initio calculations show that the effective energy barrier of 2 or 3 mainly comes from the contribution of a single Tb(III) or Dy(III) fragment, which is only about one third of a single Ln energy barrier. For 4 or 5, however, both of the two Ho(III) or Er(III) fragments contribute to the total energy barrier. Thus, it is insufficient to only increase the magnetic anisotropy energy barrier of a single Ln ion, while enhancing the Ln-bpym(-) couplings is also very important.
authors.affiliation: Physical Department, Jiangsu Key Laboratory for NSLSCS, School of Physical Science and Technology, Nanjing Normal University, Nanjing, 210023, People's Republic of China.
authors.forename: Yi-Quan
authors.initials: YQ
authors.lastname: Zhang
authors.forename: Cheng-Lin
authors.initials: CL
authors.lastname: Luo
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
mesh_terms: D016880:Anisotropy; D005609:Free Radicals / Q000737:chemistry; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D060526:Magnetic Fields; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011743:Pyrimidines / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D005609:Free Radicals; D028581:Lanthanoid Series Elements; D009942:Organometallic Compounds; D011743:Pyrimidines
keywords: B3LYP; complete-active-space self-consistent field; energy barrier; exchange coupling; single-molecule magnet