A Novel 1:1 Co-Crystal of Bis(1,10-Phenanthroline)(1,10-Phenanthroline-5,6-Dione)Nickel(II) Hexafluorophosphate and Tris(1,10-Phenanthroline)Nickel(II) Hexafluorophosphate Complexes, [Ni(phen)2(phen-dione)] [Ni(phen)3] (PF6)4

Abstract

The purpose of this study was to investigate whether co-crystals form by simply mixing pure solutions of [Ni(phen)3](PF6)2 and [Ni(phen)2(phen-dione)](PF6)2 where phen is 1,10-phenanthroline and phen-dione is 1,10-phenanthroline-5,6-dione. The 1:1 cocrystal, [Ni(phen)2(phen-dione)][Ni(phen)3](PF6)4·CH3CN has been characterized by elemental analysis, IR, paramagnetic NMR, and UV–vis spectroscopies, cyclic voltammetry, and single crystal X-ray structure analysis. The title complex crystallized in triclinic crystal system (z = 2) with space group of Pī, a = 13.201(2) A, b = 14.782(3) A, c = 22.294(4) A, α = 81.575(15)o, β = 88.756(15)o, γ = 88.032(15)o and V = 4300.1(14) A3. A careful inspection of the packing pattern in the lattice reveals that non-covalent interactions of three different types, viz. C–H···F, C=O···H−C and C−H···π interactions, are active in the lattice. The coordination around the Ni(II) centers is a distorted octahedral, with bite angles of 78.3−79.8o for the chelating phen and phen-dione ligands. Cyclic voltammetry of this co-crystal shows that the Ni(III/II) couple is quasi-reversible. The effective magnetic moment (μeff) of the co-crystal was measured to be 2.87 BM per Ni(II) ion by Evans method. The magnitude of μeff is consistent with magnetic moment for octahedral Ni(II) complexes. The purpose of this study was to investigate whether co-crystals form by simply mixing pure solutions of [Ni(phen)3](PF6)2 and [Ni(phen)2(phen-dione)](PF6)2 where phen is 1,10-phenanthroline and phen-dione is 1,10-phenanthroline-5,6-dione.