title: Tuning the coordination geometries and magnetic dynamics of [Ln(hfac)4](-) through alkali metal counterions.
abstract: Four lanthanide compounds with formulas [Cs{Dy(hfac)4}] (1), [Cs{Er(hfac)4}] (2), [K{Dy(hfac)4}] (3), and [K{Er(hfac)4}] (4) (hfac = hexafluoroacetylacetone) are reported. Compounds 1 and 2 crystallize in the orthorhombic Pbcn space group, while 3 and 4 are in the triclinic P1̅ space group. All display chain structures in which the mononuclear [Ln(hfac)4](-) anions are linked by alkali metal ions. However, the coordination geometries around the Ln atoms are quite different depending on the cation. They adopt a distorted dodecahedron with pseudo-D2d symmetry in the cesium compounds 1 and 2, while a distorted square-antiprism with pseudo-D4d symmetry is adopted in the potassium compounds 3 and 4. The latter compounds show distinct field-induced slow magnetization relaxation. The energy barriers are 23.95 and 20.21 K for compounds 3 and 4, respectively.
authors.affiliation: State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University , Nanjing 210093, China.
authors.forename: Dai
authors.initials: D
authors.lastname: Zeng
authors.forename: Min
authors.initials: M
authors.lastname: Ren
authors.forename: Song-Song
authors.initials: SS
authors.lastname: Bao
authors.forename: Li-Min
authors.initials: LM
authors.lastname: Zheng