title: Ferromagnetic Interactions between Imino Nitroxides through Diamagnetic Metal Ions: Crystal Structures, Magnetism, and Electronic Properties of [M(I)(imino nitroxide)(2)](PF(6)) (M = Cu(I) and Ag(I)).
abstract: An orthogonal arrangement of imino nitroxide ligands in Cu(I) and Ag(I) complexes results in propagation of an intramolecular ferromagnetic interaction between the coordinated imino nitroxides through these diamagnetic ions. Reaction of [Cu(I)(CH(3)CN)(4)](PF(6)) and Ag(I)(PF(6)) with imino nitroxides in ethanol solution gave [Cu(I)(immepy)(2)](PF(6)) (1) and [Ag(I)(impy)(2)](PF(6)) (2), respectively (immepy = 2-(2-(6-methylpyridyl))-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy and impy = 2-(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy). Complex 1 crystallizes in the orthorhombic space group Pba2, which has a unit cell with a = 11.251(2) Å, b = 14.745(3) Å, c = 9.747(2) Å, V = 1617.0(5) Å(3), and Z = 2. Refinement with 991 reflections observed [|I(o)| > 3sigma(I(o))] gave R = 0.044 (R(w) = 0.053). In 1, imino nitroxides coordinate to the Cu(I) ions in a tetrahedral fashion, the dihedral angle between coordinating imino nitroxides being 88.7 degrees. Magnetic susceptibility measurement for 1 shows typical triplet-singlet behavior with strong ferromagnetic interactions (J = 55.1(6) cm(-)(1) with g = 2.0; H = -JS(1)().S(2)()). The UV-visible absorption spectrum of 1 shows strong bands at 464 and 766 nm assignable to charge-transfer bands from the Cu ion to the ligand NLUMO and SOMO, respectively. The pi-back-donation to the SOMO induces the spin on the Cu ion and results in the strong ferromagnetic interaction. Complex 2 crystallizes in the orthorhombic space group P2(1)cn which has a unit cell with a = 10.535(6) Å, b = 31.295(3) Å, c = 8.921(4) Å, V = 2941(1) Å(3), and Z = 4. Refinement with 1882 reflections [|I(o)| > 3sigma(I(o))] gave R = 0.058 (R(w) = 0.074). In 2, the four coordination sites of the Ag(I) ion were completed with two imino nitroxides and the dihedral angle between the imino nitroxides is 79.2 degrees. The EPR spectrum of a frozen ethanol solution of 2 shows a typical triplet signal with zero field splitting (|D| = 0.043 cm(-)(1) and |E| = 0.014 cm(-)(1)). Curie plots for the Deltam = 2 signal below 80 K gave a positive Weiss constant (theta = 4 K), suggesting an intramolecular ferromagnetic interaction in 2.
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-77, Japan, and Institute for Chemical Reaction Science, Tohoku University, Aoba-ku, Sendai 980-77, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Oshio
authors.forename: Takashi
authors.initials: T
authors.lastname: Watanabe
authors.forename: Akihiro
authors.initials: A
authors.lastname: Ohto
authors.forename: Tasuku
authors.initials: T
authors.lastname: Ito
authors.forename: Tadaaki
authors.initials: T
authors.lastname: Ikoma
authors.forename: Shozo
authors.initials: S
authors.lastname: Tero-Kubota