TY - JOUR
T1 - Study on spin configuration in photoresponsive iron mixed-valence complexes by Mössbauer spectroscopy
AU - Okazawa, A.
AU - Yoshida, J.
AU - Kida, N.
AU - Kashima, I.
AU - Murata, W.
AU - Enomoto, M.
AU - Kojima, N.
N1 - Funding Information:
Acknowledgement This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Educational Science, Sports and Culture, Japan.
PY - 2014/4
Y1 - 2014/4
N2 - We have investigated magnetic properties in a series of photoresponsive dithiooxalato (dto)-bridged iron mixed-valence complexes, (SP-R)[FeIIFeIII(dto)3] (SP-R = R-substituted pyridospiropyran cation; R = Me, Et, and Pr; abbreviated as 1 Me, 1 Et, and 1 Pr, respectively). As for our previous reports, 1 Me and 1 Et show two-step succeeding ferromagnetic transitions at T C = 25 & 8 K and 22 & 5 K, respectively. However, 1 Et has no hysteresis in the magnetic susceptibility, while 1 Me undergoes the charge transfer phase transition with thermal hysteresis around 75 K. To elucidate the two-step transitions of them, we measured 57Fe Mössbauer spectra of 1 Et. The spectra of FeII (S = 2) and FeIII (S = 1/2) in the HTP were observed in the magnetically ordered state as well as the paramagnetic state, and revealed that only HTP exists in a temperature range up to 5 K. The result is consistent with that of 1 Pr, where one ferromagnetic phase transition occurs at T C = 10 K. 57Fe Mössbauer spectroscopy is useful to clarify the origin of the succeeding magnetic transition for these systems.
AB - We have investigated magnetic properties in a series of photoresponsive dithiooxalato (dto)-bridged iron mixed-valence complexes, (SP-R)[FeIIFeIII(dto)3] (SP-R = R-substituted pyridospiropyran cation; R = Me, Et, and Pr; abbreviated as 1 Me, 1 Et, and 1 Pr, respectively). As for our previous reports, 1 Me and 1 Et show two-step succeeding ferromagnetic transitions at T C = 25 & 8 K and 22 & 5 K, respectively. However, 1 Et has no hysteresis in the magnetic susceptibility, while 1 Me undergoes the charge transfer phase transition with thermal hysteresis around 75 K. To elucidate the two-step transitions of them, we measured 57Fe Mössbauer spectra of 1 Et. The spectra of FeII (S = 2) and FeIII (S = 1/2) in the HTP were observed in the magnetically ordered state as well as the paramagnetic state, and revealed that only HTP exists in a temperature range up to 5 K. The result is consistent with that of 1 Pr, where one ferromagnetic phase transition occurs at T C = 10 K. 57Fe Mössbauer spectroscopy is useful to clarify the origin of the succeeding magnetic transition for these systems.
KW - Dithiooxalate
KW - Mixed-valence complex
KW - Mössbauer spectroscopy
KW - Photoisomerization
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U2 - 10.1007/s10751-013-0934-2
DO - 10.1007/s10751-013-0934-2
M3 - Article
AN - SCOPUS:84901194100
SN - 0304-3843
VL - 226
SP - 351
EP - 357
JO - Hyperfine Interactions
JF - Hyperfine Interactions
IS - 1-3
ER -