Akio Nakamoto

On-off optical switching of the magnetic and structural properties in a spin-crossover complex

A photoexcitation is one of the promising external fields to control the material phases. Here, the authors have demonstrated that the magnetic and structural properties of a spin-crossover complex, Fe(phen)2(NCS)2 (phen=1,10-phenanthroline), can be reversibly switched by the on-off action of the continuous photoexcitation at the same temperature. The structural data suggest that the density of the high-spin Fe2+ in the photoinduced phase is about 0.88. Suppressed atomic vibrations of the photoinduced phase exclude the conventional heating effect as the origin for the observed optical switching.

Strcutural Analysis of [Fe(ptz)6)](BF4)2 under Photo-Excitation –Condensation of Photo-Excited High-Spin Ions–

We have performed in situ synchrotron-radiation X-ray powder structural analysis in a spin-crossover complex ([Fe(ptz) 6 )](BF 4 ) 2 : ptz = propyltetrazole) under a photo-excitation with a continu...

Low-Temperature Structure of [Fe(ptz)6](BF4)2. Determination by Synchrotron-Radiation X-ray Powder Study.

Temperature dependence of atomic coordinates is precisely determined for an iron (II) complex, [Fe(ptz) 6 ](BF 4 ) 2 (ptz = propyltetrazole), by means of synchrotron-radiation (SR) x-ray powder diffraction measurements. The spin state of the Fe 2+ ions is known to change from high-spin (HS; S = 2) to low-spin (LS; S = 0) with a decrease in temperature to below T c ≈130 K. We have found that the spin state transition accompanies a significant contraction of the Fe–N4 bond distance from ≈ 2.20 A (HS) to ≈ 2.00 A (LS).

Dynamical Phase Transition in a Spin-Crossover Complex

Density n HS of photoexcited high-spin (HS) sites in a spin–crossover film (Nafion-[Fe(Htrz) 3 ]; Htrz = 1,2,4-4H-triazole) was systematically investigated against temperature T and excitation power density P . At low temperatures (≤35 K), the n HS – P curve shows a nonlinear increase when P reaches a critical value ( P c ). We interpreted the increase in terms of the dynamical phase transition into the condensed state of photoexcited HS molecules, and derived the P – T phase diagram. The P – T phase diagram and the n HS – P curves were analyzed with an Ising-like model which includes a temperature-dependent field.

Spin transition and its photo-induced effect in spin crossover complex film based on [Fe(II)(trz)3]

We have synthesized the [Fe(II)(Htrz) 3 ] complex film by using ion-exchange film (Nafion) as counter anion. From the analysis of Fe Kedge EXAFS spectra, we could prove the existence of one-dimensional Fe chain structure, [Fe(II)(Htrz) 3 ] n on Nafion film. [Fe(II)(Htrz) 3 ]-Nafion showed a spin crossover phenomenon around room temperature. Moreover, the LIESST(Light Induced Spin State Trapping) effect was observed at 4.2 K.

Photoinduced axial bond exchange reaction of dichlorophosphorus(V)tetraphenylporphyrin chloride: photochemical activation of central three-centre four-electron bond through the σ–π interaction

A novel photoinduced axial bond exchange reaction of dichlorophosphorus(V)tetraphenylporphyrin chloride in various alcohols affords axial dialkoxyphosphorus(V)tetraphenylporphyrin derivatives.

Photoemission study of temperature-induced and photoinduced spin-state transitions in spin-crossover complex [Fe(ptz)6](BF4)2

We report an x-ray photoemission spectroscopy study of spin-crossover complex [Fe(ptz) 6 ](BF 4 ) 2 (ptz = 1-propyltetrazole) to identify the electronic changes due to temperature-induced and photoinduced spin transitions. The energy difference between the Fe 2 p and F 1 s peaks is found to correlate with the low-spin (LS) to high-spin (HS) transition of [Fe(ptz) 6 ](BF 4 ) 2 . The Fe 2 p 3/2 spectrum of the HS state is accompanied by a charge-transfer satellite and is analyzed by configuration-interaction cluster-model calculations. Based on the electronic-structure parameters from the cluster-model analysis, the stability of the LS state against the HS state is calculated as a function of the Fe–N bond length. A drastic bond-length reduction is required to stabilize the LS state and is also related to the observed core-level shift. The postillumination spectral shape well reproduces the spectrum before the laser illumination, suggesting that the surface of the Fe complex is chemically stable against the...