Mononuclear nickel(II) complexes coordinated by polypyridyl ligands

Abstract Three mononuclear polypyridyl complexes of Ni(II), [Ni(Ph 2 phen) 3 ](PF 6 ) 2 ·CH 3 CN ( 1 ), [Ni(dpa) 2 (phen)](PF 6 ) 2 ( 2 ) and [Ni(bpy) 3 ](PF 6 ) 2 ( 3 ), where Ph 2 phen is 4,7-diphenyl-1,10-phenanthroline, dpa is 2,2′-dipyridylamine, bpy is 2,2′-bipyridine, and phen is 1,10-phenanthroline, were prepared and their solid state structures determined by single-crystal X-ray crystallography. The structural determination shows that the coordination geometry around the Ni(II) center is a distorted octahedron in each complex. The investigation of synthesis procedure and crystallographic data of complex 3 indicates the spontaneous resolution of supramolecular chirality. A careful inspection of the packing pattern in the lattice of each complex reveals that non-covalent interactions of two different types, viz . C–H⋯F and C–H⋯ π interactions, are active in the lattice. The packing structures of 1 – 3 also show that the rings of the polypyridyl ligands, Ph 2 phen, dpa, bpy, and phen, are not located face-to-face and can not interact through π – π interactions. Cyclic voltammetry data of 1 and 3 show that the Ni(III/II) reduction couple is quasi-reversible and this reduction becomes progressively more difficult on passing from bpy to Ph 2 phen, while complex 2 shows an irreversible behavior with the peak-to-peak separation of about 500 mV. Magnetic susceptibility data derived from paramagnetic NMR revealed effective magnetic moments of 3.12 BM for 1 , 3.27 BM for 2 , and 3.14 for 3 at room temperature.