No abstract

Simple cationic sandwich complexes that contained alkyl- or halogen substituents provided ionic liquids (ILs) with the bis(perfluoroalkanesulfonyl)imide anion. Ferrocenium- and cobaltocenium ILs [M(C(5)H(4)R(1))(C(5)H(4)R(2))][Tf(2)N] (M=Fe, Co) and arene-ferrocenium ILs [Fe(C(5)H(4)R(1))(C(6)H(5)R(2))][Tf(2)N] were prepared and their physical properties were investigated. A detailed comparison of their thermal properties revealed the effects of molecular symmetry and substituents on their melting points. Their viscosity increased on increasing the length of the substituent on the cation and the perfluoroalkyl chain length on the anion. Upon cooling, ILs with low viscosities exhibited crystallization, whereas those with higher viscosities tended to exhibit glass transitions. Most of these salts showed phase transitions in the solid state. A magnetic-switching phenomenon was observed for the paramagnetic ferrocenium IL, which was associated with a liquid/solid transformation, based on the magnetic anisotropy of the ferrocenium cation. (57)Fe Mössbauer spectroscopy was applied to [Fe(C(5)H(4)nBu)(2)][Tf(2)N] to investigate the vibrational behavior of the iron atom in the crystal and glassy states of the ferrocenium IL.

A new spin crossover (SCO) coordination polymer, {[Fe(II)(4-methylpyridine)(2)][Au(I)(CN)(2)](2)}(n) () has been synthesized. The complex () has been observed to have a thermal induced three-step SCO transition, which is unprecedented behavior as compared with existing SCO complexes. In the complex, about 18%, 41% and 41% high spin states are changed to low spin states in the first-step, second-step and third-step, respectively.

A two-dimensional network compound, [{Mn(saltmen)}4{Co(CN)6}](ClO4)·9H2O (2) (saltmen2− = N,N′-(1,1,2,2-tetramethylethylene)bis(salicylideneiminate)), was synthesized. Magnetic measurements characterized the [Mn2(saltmen)2]2+ subunit as a single-molecule magnet with an ST = 4 spin ground state, indicating that the MnIII dimer is magnetically isolated not only by the diamagnetic [Co(CN)6]3− unit but also by the space between the layers.

A new hetero-metal 2-dimensional (2D) spin-crossover complex, {[FeII(3-Fpy)2][AuI(CN)2]2}n (3-Fpy = 3-fluoropyridine) has been synthesized and characterized crystallographically and magnetically. The complex consists of an octahedral FeII ion and a mononuclear [AuI(CN)2]− unit with a linear coordination geometry which combine to form an infinite 2D structure. The spin transition observed for this complex is accompanied by a drastic and reversible change of color from blue to purple.