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A Brønsted‐Ligand‐Based Iron Complex as a Molecular Switch with Five Accessible States
Author(s) -
Shiga Takuya,
Saiki Ryo,
Akiyama Lisa,
Kumai Reiji,
Natke Dominik,
Renz Franz,
Cameron Jamie M.,
Newton Graham N.,
Oshio Hiroki
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201900909
Subject(s) - deprotonation , spin crossover , ligand (biochemistry) , chemistry , spin states , pyridine , benzimidazole , molecular switch , crystallography , protonation , spin transition , stereochemistry , medicinal chemistry , molecule , inorganic chemistry , organic chemistry , receptor , ion , biochemistry
A mononuclear Fe II complex, prepared with a Brønsted diacid ligand, H 2 L (H 2 L=2‐[5‐phenyl‐1 H ‐pyrazole‐3‐yl] 6‐benzimidazole pyridine), shows switchable physical properties and was isolated in five different electronic states. The spin crossover (SCO) complex, [Fe II (H 2 L) 2 ](BF 4 ) 2 ( 1 A ), exhibits abrupt spin transition at T 1/2 =258 K, and treatment with base yields a deprotonated analogue [Fe II (HL) 2 ] ( 1 B ), which shows gradual SCO above 350 K. A range of Fe III analogues were also characterized. [Fe III (HL)(H 2 L)](BF 4 )Cl ( 1 C ) has an S =5/2 spin state, while the deprotonated complexes [Fe III (L)(HL)], ( 1 D ), and (TEA)[Fe III (L) 2 ], ( 1 E ) exist in the low‐spin S =1/2 state. The electronic properties of the five complexes were fully characterized and we demonstrate in situ switching between multiple states in both solution and the solid‐state. The versatility of this simple mononuclear system illustrates how proton donor/acceptor ligands can vastly increase the range of accessible states in switchable molecular devices.