Single-Molecule Magnets: Tetranuclear Vanadium(III) Complexes with a Butterfly Structure and an S ) 3 Ground State

摘要: Reactions of VCl3(THF)3, bpy, and NaO2CR (R = Et, Ph; bpy 2,2‘-bipyridine) in a 1:1:3 ratio Me2CO give [V4O2(O2CR)7(bpy)2](ClO4) 1; R Ph, 4) following addition NBun4ClO4. Use 4,4‘-dimethyl- or 5,5‘-dimethylbipyridine (4,4‘-Me2bpy 5,5‘-Me2bpy, respectively) Et leads similarly to [V4O2(O2CEt)7(L−L)2](ClO4) (L−L 4,4‘-Me2bpy, 2; L−L 3). Yields are the 38−90% range. The cation 1 is isostructural with previously prepared [M4O2(O2CR)7(bpy)2]+ (M CrIII, MnIII, FeIII) species possesses [V4O2] butterfly core. 1D 2D COSY 1H NMR spectra show solid-state structure retained on dissolution. effective magnetic moment (μeff) per V4 for gradually rises from 5.79 μB at 300 K maximum 6.80 25.0 then decreases rapidly 4.72 2.00 K. data 7.00−300 range were fit appropriate theoretical expression (based Ĥ −2JSi·Sj) Jbb −31.2 cm-1, Jwb +27.5 g 1.82, (b body, w wing...