Abstract
Three mononuclear polypyridyl complexes of Ni(II),
Ni(Ph(2)phen)(3)(PF(6))(2)center dot 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 center dot
center dot center dot F and C-H center dot center dot center dot pi
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
pi-pi 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. (C) 2011 Elsevier
Ltd. All rights reserved.
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