Carboxylate Bridge Controlled Formation of Tetra‐ and Pentanuclear Nickel(II) Complexes: Synthesis, Crystal Structure, Spectroscopy and Magnetic Properties
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E-Artikel
Titel:
Carboxylate Bridge Controlled Formation of Tetra‐ and Pentanuclear Nickel(II) Complexes: Synthesis, Crystal Structure, Spectroscopy and Magnetic Properties
Beschreibung:
AbstractA carboxyamine functionalized tridentate ligand in combination with three different carboxylate bridging groups (RCO2−; R=CH3, C2H5 and CF3) has been utilized to prepare tetra‐ and pentanuclear nickel(II) complexes, [Ni4(L)2(μ3‐OCH3)2(μ1,1‐O2CCH3)2(μ1,3‐O2CCH3)2(CH3OH)2] (1), [Ni4(L)2(μ3‐OCH3)2(μ1,1‐O2CC2H5)2(μ1,3‐O2CC2H5)2(CH3OH)2] (2) and [Ni5(L)4(μ3‐OH)2(μ1,3‐O2CCF3)2]Br2⋅3H2O (3) (HL=3‐[(2‐pyridylmethyl)‐amino]‐propionic acid). The complexes have been characterized using several techniques such as elemental analysis, solution electrical conductivity, FTIR and UV‐Vis spectroscopy, and low temperature magnetic measurements. While complex 1 and 3 were further characterized using single crystal X‐ray diffraction, molecular structure of complex 2 has been optimized using DFT calculation. Whereas the acetate/propionate groups deliver Ni4 cluster, the trifluoroacetate group provides Ni5 assembly. Molecular structures of complexes 1 and 2 comprise a central [Ni4O6] core that could be described as a distorted face‐shared dicubane with two missing vertices. On the other hand, the [Ni5(μ3‐OH)2(μ1,3‐O2CCF3)2]6+ structural core of complex 3 contains five coplanar nickel(II) ions in a rectangular organization. Variable‐temperature magnetic susceptibility studies reveal the interesting magnetic properties of complexes 1 and 3. While complex 1 shows both ferro‐ and antiferromagnetic interactions with J1=−1.10 cm−1, J2=+2.40 cm−1 and J3=−0.65 cm−1, complex 3 exhibits only ferromagnetic interactions with J1=+2.0 cm−1 and J2=+1.0 cm−1.