Synthesis, Structure, Magnetism and Electrochemical Properties of Linear Pentanuclear Complex: Ni5(µ‐dmpzda)4(NCS)2

Abstract

Abstract The synthesis, crystal structure, electrochemical and magnetic properties of a type of pyridine‐modulated linear pentanuclear complex, [Ni5(µ‐dmpzda)4(NCS)2] [dmpzda‐H2=N,N′‐di(4‐methyl pyridin‐2‐yl)pyrazine‐2,6‐diamine], were studied. The complex involves a Ni5 linear chain unit with all of the Ni‐Ni‐Ni being nearly 180°, terminated by the two axial ligands. This pentanuclear linear metal chain is helically wrapped by four syn‐syn‐syn‐syn type dmpzda ligands. There are two types of Ni–Ni distances existing in the complex. The terminal Ni–Ni distances bonded with the axial ligand are longer (2.3821 Å) affected by the axial ligands. The inner Ni–Ni distances are very short and remain constant (2.2959 Å). Two terminal Ni(II) ions bonded with the axial ligands are in a square‐pyramidal (NiN4NCS) environment and exhibit long Ni–N bonds (2.103 Å), which are consistent with a high‐spin Ni(II) configuration. The inner three Ni(II) ions display short Ni–N (1.886–1.906 Å) bond distances, which are consistent with a squareplanar (NiN4), diamagnetic arrangement of a low‐spin Ni(II) configuration. This compound exhibits similar [Ni5(µ‐tpda)4(NCS)2] magnetic behavior, indicating an antiferromagnetic interaction of two terminal high‐spin Ni(II) ions in these complexes.