Reversible transformation between an ionic liquid and a coordination polymer by application of light and heat has been achieved. Ultraviolet light irradiation transforms the transparent liquid to a yellow solid; a reverse reaction occurs due to the application of heat. The transformation accompanies drastic switching of intra- and intermolecular coordination bonds of a ruthenium complex. This is a novel material conversion methodology that connects the fields of ionic liquids and coordination polymers.

Ionic liquids comprised of cationic arene− r u t h e n i u m c h e l a t e c o m p l e x e s a n d t h e b i s -(trifluoromethanesulfonyl)amide anion (=Tf 2 N), [(arene)-RuCl(L)](Tf 2 N), where L = MeS(CH 2 ) n SR (R = Me, Bu; n = 1−3), Me 2 N(CH 2 ) 2 NMe 2 and arene = p-cymene, C 6 H 6 , have been prepared, and their thermal properties, structures, and reactivities have been investigated. These liquids undergo direct ligand exchange reactions in line with their thermal stabilities. Thermogravimetric analysis revealed that the thermal stabilities of the complexes are higher as the bridging group of the chelate ligand becomes longer. The complexes with MeSCH 2 SMe transform thermally into dinuclear complexes. The coordination structures were determined crystallographically.

The reactions of [CpRu(NCMe) 3 ] + and 1,2-disubstituted benzene ligands (L) bearing donor substituents were examined to investigate the consequence of competing coordination modes. 1,2-C 6 H 4 (OMe) 2 and 1,2-C 6 H 4 (SMe)(OMe) produce [CpRu(η 6 -L)] +type sandwich complexes with a η 6 coordination mode, whereas 1,2-C 6 H 4 (SMe) 2 forms the chelate complex [CpRu(κ 2 -L)(NCMe)] + , due to the coordination ability of the donor atoms. 1,2-C 6 H 4 (NMe 2 ) 2 and 1,2-C 6 H 4 (SMe)(NMe 2 ) produce the sandwich complexes or the chelate complexes ([CpRu(κ 2 -L)(NCMe) n ] + ; n = 0 or 1) depending on the reaction conditions. The chelate complexes are the kinetic products and are thermally transformed into the sandwich complexes in solution. The hexafluorophosphate (PF 6 ) and bis-(trifluoromethylsulfonyl)amide (Tf 2 N) salts were isolated, and their thermal properties were investigated. The Tf 2 N salts of the sandwich complexes are room-temperature ionic liquids. The molecular structures were determined crystallographically.

In order to understand an effect of crack-face bridging stress field of alumina ceramics on its fracture toughness, local residual stress distribution due to crack face grain bridging behind the crack tip was measured using synchrotron x-ray beam at SPring-8 in Japan. The SEPB (Single Edge Precracked Beam) specimens of two types of polycrystalline Al2O3 were used for stress measurement; one was pressureless sintered Al2O3 (AL1) and the other was hot-press sintered Al2O3 (TAL). Pop-in precracks were introduced by bridge-indentation method. Before residual stress mapping, the SEPB specimens were unloaded from a constant applied load to zero using four points bending device. Two-dimensional residual stress field was mapped by scanning a micro X-ray beam of 50×50 μm2 with the scanning interval of 12.5 or 25 μm. As a result, in the case of AL1 having conventional fracture toughness and strength, the compressive residual stresses due to crack-face bridging were only observed in the close vicinity of crack tip. On the other hand, in the case of TAL having higher fracture toughness and strength, the compressive residual stresses were widely distributed behind the crack tip. Larger compressive stress was locally generated along the crack path at interlocked grains. The compressive bridging stresses distributed behind the crack tip were found to enlarge with a decrease in the crack opening displacement against a constant applied stress intensity factor, Kapp. It was concluded that the difference in residual stress fields behind crack tip was attributed to the differences in its microstructure and microcrack propagation behavior, such as deflections and interlocked grains.

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