We report a unique synthetic route toward the multistep spin crossover (SCO) effect induced by utilizing the partial ligand transformation during the crystallization process, which leads to the incorporation of three different Fe II complexes into a single coordination framework. The 3acetoxypyridine (3-OAcpy) molecules were introduced to the self-assembled Fe II −[M IV (CN) 8 ] 4− (M = Mo, Nb) system in the aqueous solution which results in the partial hydrolysis of the ligand into 3-hydroxypyridine (3-OHpy). It gives two novelThey exhibit an unprecedented cyanido-bridged skeleton composed of {Fe 3 M 2 } n coordination nanotubes bonded by additional Fe complexes. These frameworks contain three types of Fe sites differing in the attached organic ligands, [Fe1(3-OAcpy) 4 (μ-NC) 2 ], [Fe2(3-OHpy) 4 (μ-NC) 2 ], and [Fe3(3-OAcpy) 3 (3-OHpy)(μ-NC) 2 ], which lead to the thermal two-step Fe II SCO, as proven by X-ray diffraction, magnetic susceptibility, UV− vis−NIR optical absorption, and 57 Fe Mossbauer spectroscopy studies. The first step of SCO, going from room temperature to the 150−170 K range with transition temperatures of 245(5) and 283(5) K for FeMo and FeNb, respectively, is related to Fe1 sites, while the second step, occurring at the 50−140 K range with transition temperatures of 70(5) and 80(5) K for FeMo and FeNb, respectively, is related to Fe2 sites. The Fe3 site with both 3-OAcpy and 3-OHpy ligands does not undergo the SCO at all. The observed two-step SCO phenomenon is explained by the differences in the ligand field strength of the Fe complexes and the role of their alignment in the coordination framework. The simultaneous application of two related pyridine derivatives is the efficient synthetic route for the multistep Fe II SCO in the cyanido-bridged framework which is a promising step toward rational design of advanced spin transition molecular switches.

We report a spin crossover material based on a cyanido-bridged FeII–MoIV assembly, FeII2[MoIV(CN)8](1-(3-pyridyl)ethanol)8⋅4H2O. This compound has a cubic crystal structure in the Ia3¯d space group and is composed of a three-dimensional cyanido-bridged FeII–MoIV coordination network with one crystallographic FeII site. It exhibits incomplete spin crossover, because 21% of the high-spin FeII sites (S = 2) changes to low-spin FeII sites (S = 0) in the temperature range between 200 and 50 K. Thermal hysteresis is not observed. Such an incomplete and gradual spin crossover is attributed to the elastic frustration between the high-spin and the low-spin FeII sites (e.g., alternating arrangement such as –HS–LS–HS–LS–).

Incorporating chiral organic ligands into cyanido-bridged FeII–NbIV assemblies synthesized chiral spin-crossover complexes, FeII2[NbIV(CN)8](L)8·6H2O (L = R-, S-, or rac-1-(3-pyridyl)ethanol: R-FeNb, S-FeNb, or rac-FeNb). Rietveld analyses based on a racemic complex...

The effect of the flash event (FE) on microcrack healing behavior in 8 mol% yttria‐stabilized zirconia was examined at healing temperatures of 1040 and 1230°C under the direct and alternating (DC and AC) electric fields. The crack healing behavior changed depending on the factors of the electric field, healing temperature, and crack length. Although the crack healing proceeded with the temperature, the healing rate increased with the crack length, suggesting that the external energy stored as crack surface energy would provide a driving force for the crack healing. Although the crack healing occurs even under the static annealing without the electric field, the healing rate was accelerated by FE significantly more under the AC field than under the DC field. The microcracks with a length of ≈20 μm were fully healed at 1230°C only for 10 min by the FE treatment under the AC field, and the flash healing behavior was four times faster than that of the static annealing. These results suggest that the enhanced healing behavior cannot be explained only by thermal effects, and the accelerated diffusivity caused additionally by nonthermal effect under FE might contribute to the enhanced healing behavior, especially in the AC electric field.