Macrocycles based on magnetically functionalized zirconium oxide clusters

作者：Malaestean Iurii L; Kutluca Meliha; Speldrich Manfred; Ellern Arkady; Koegerler Paul

来源：Inorganica Chimica Acta, 2012, 380: 72-77.

DOI：10.1016/j.ica.2011.08.061

• Heterometallic complexes
• Magnetic properties
• Zirconium compounds
• Macrocycles

In the presence of 4,4%26apos;-bipyridine and Co(II) or Ni(II) groups, which are coordinatively constrained by bis-alkoxyamine chelating groups, dimeric [(Zr6O4)-O-IV(OH)(4)(RCOO)(12)](2) clusters rearrange to {Zr12O11(OH)(11)(RCOO)(16)} frameworks featuring highly condensed zirconium oxide cores. These {Zr-12} groups subsequently each coordinate to three M(II) groups and self-assemble via two bridging 4,4%26apos;-bpy into 2.6 nm {M6Zr24}type macrocycles of composition [M6Zr24O22(OH)(22)(C2H5COO)(40)(Hmdea)(2)(H(2)mdea)(4)(4,4%26apos;-bpy)(2)]. Surprisingly, two M(II) sites peripherally attached to the {Zr-12} frameworks adopt a rare eightfold coordination mode where the M2+ ions reside in a distorted square antiprismatic O7N environment. Magnetic measurements reveal that the zirconium oxide fragments efficiently mediate antiferromagnetic exchange between Ni2+ spin centers, whereas in case of the virtually isostructural Co2+ derivative pronounced ligand field asymmetry causes single-ion effects to significantly influence the low-field susceptibility data.

• 出版日期2012-1-15