TY - JOUR
T1 - Structural Insight into Order-Disorder Transition and Charge-Transfer Phase Transition in an Iron Mixed-Valence Complex (n-C3H7)4N[FeIIFeIII(dto)3] with a Two-Dimensional Honeycomb Network
AU - Itoi, Miho
AU - Okazawa, Atsushi
AU - Yamaura, Jun Ichi
AU - Maki, Sachiko
AU - Komatsu, Tokutaro
AU - Maurin, Isabelle
AU - Codjovi, Epiphane
AU - Boukheddaden, Kamel
AU - Kojima, Norimichi
N1 - Funding Information:
The authors thank Profs. F. Varret (Universitè de Versailles Saint-Quentin-en-Yvelines), Y. Kobayashi (Tokyo Medical University), M. Enomoto (Tokyo University of Science), and N. Matsushita (Rikkyou University) for helpful discussions. The DFT calculations were performed on the supercomputer at ACCMS, Kyoto University. SEM measurements were carried out at the Electron Microscopy Laboratory of the Medical Research Support Center in the Nihon University School of Medicine. This work was supported by a Grant-in-Aid for Scientific Research and a Grand-in-Aid from the 21st Century COE (Center of Excellence) Program (E05: Research Center for Integrated Science) from the Ministry of Education, Science, Sports and Culture, Japan, and the Research Budget from the Nihon University School of Medicine.
Funding Information:
This work was supported by a Grant-in- Aid for Scientific Research and a Grand-in-Aid from the 21st Century COE (Center of Excellence) Program (E05: Research Center for Integrated Science) from the Ministry of Education, Science, Sports and Culture, Japan, and the Research Budget from the Nihon University School of Medicine.
Publisher Copyright:
Copyright © 2018 American Chemical Society.
PY - 2018/11/5
Y1 - 2018/11/5
N2 - The structural properties of the iron mixed-valence complex (n-C3H7)4N[FeIIFeIII(dto)3] (dto = dithiooxalato, C2O2S2) have been investigated by single-crystal X-ray diffraction (SCXRD) at low temperatures. (n-C3H7)4N[FeIIFeIII(dto)3] has two-dimensional (2D) honeycomb layers consisting of alternating FeII and FeIII arrays bonded by bis-bidentate dithiooxalato ligands. Upon cooling, a superlattice structure with q = (1/3, 1/3, 0) was observed below 260 K, which corresponds to an order-disorder transition of the (n-C3H7)4N+ ions between the honeycomb layers. The charge-transfer phase transition (CTPT) occurs at TC→1/2 ∼ 120 K and TC↑1/2 ∼ 90 K upon heating and cooling, respectively, with an electron transfer between the FeII and FeIII ions, accompanied by a spin-state change, FeII (S = 2; HS)-O2C2S2-FeIII (S = 1/2; LS) ↔ FeIII (S = 5/2; HS)-O2C2S2-FeII (S = 0; LS). During the CTPT, the intersheet [FeIIFeIII(dto)3] distance decreased monotonously upon cooling, and an abrupt structural contraction was observed in the hexagonal 2D network. The volume contraction during the CTPT was quite small (∼0.7%), and differences in the structural distortions at the FeS6 and FeO6 sites were not found in the vicinity of the CTPT. We also calculated the orbital energies and the occupied spin states for the [Fe(O2C2S2)3] and [Fe(S2C2O2)3] octahedra in the vicinity of the CTPT by density functional theory (DFT). Because the local symmetry around the two coordinating iron ions is already lowered to trigonal symmetry, the CTPT did not cause any further deformation. This symmetry invariance resulted in an absence of orbital contributions to the total entropy change (ΔS) in the CTPT, which is in agreement with the previous heat capacity measurements. [Nakamoto, T; Miyazaki, Y; Itoi, M; Ono, Y; Kojima, N; Sorai, M. Heat Capacity of the Mixed-Valence Complex {[(n-C3H7)4N][FeIIFeIII(dto)3]}∞, Phase Transition because of Electron Transfer, and a Change in Spin-State of the Whole System. Angew. Chem., Int. Ed. 2001, 40, 4716-4719.]
AB - The structural properties of the iron mixed-valence complex (n-C3H7)4N[FeIIFeIII(dto)3] (dto = dithiooxalato, C2O2S2) have been investigated by single-crystal X-ray diffraction (SCXRD) at low temperatures. (n-C3H7)4N[FeIIFeIII(dto)3] has two-dimensional (2D) honeycomb layers consisting of alternating FeII and FeIII arrays bonded by bis-bidentate dithiooxalato ligands. Upon cooling, a superlattice structure with q = (1/3, 1/3, 0) was observed below 260 K, which corresponds to an order-disorder transition of the (n-C3H7)4N+ ions between the honeycomb layers. The charge-transfer phase transition (CTPT) occurs at TC→1/2 ∼ 120 K and TC↑1/2 ∼ 90 K upon heating and cooling, respectively, with an electron transfer between the FeII and FeIII ions, accompanied by a spin-state change, FeII (S = 2; HS)-O2C2S2-FeIII (S = 1/2; LS) ↔ FeIII (S = 5/2; HS)-O2C2S2-FeII (S = 0; LS). During the CTPT, the intersheet [FeIIFeIII(dto)3] distance decreased monotonously upon cooling, and an abrupt structural contraction was observed in the hexagonal 2D network. The volume contraction during the CTPT was quite small (∼0.7%), and differences in the structural distortions at the FeS6 and FeO6 sites were not found in the vicinity of the CTPT. We also calculated the orbital energies and the occupied spin states for the [Fe(O2C2S2)3] and [Fe(S2C2O2)3] octahedra in the vicinity of the CTPT by density functional theory (DFT). Because the local symmetry around the two coordinating iron ions is already lowered to trigonal symmetry, the CTPT did not cause any further deformation. This symmetry invariance resulted in an absence of orbital contributions to the total entropy change (ΔS) in the CTPT, which is in agreement with the previous heat capacity measurements. [Nakamoto, T; Miyazaki, Y; Itoi, M; Ono, Y; Kojima, N; Sorai, M. Heat Capacity of the Mixed-Valence Complex {[(n-C3H7)4N][FeIIFeIII(dto)3]}∞, Phase Transition because of Electron Transfer, and a Change in Spin-State of the Whole System. Angew. Chem., Int. Ed. 2001, 40, 4716-4719.]
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U2 - 10.1021/acs.inorgchem.8b02211
DO - 10.1021/acs.inorgchem.8b02211
M3 - Article
C2 - 30339001
AN - SCOPUS:85055566297
SN - 0020-1669
VL - 57
SP - 13728
EP - 13738
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 21
ER -