Carboxylic Acid Functionalized Spin-Crossover Iron(II) Grids for Tunable Switching and Hybrid Electrode Fabrication

• Published in: Inorganic chemistry 2018-11, Vol.57 (22), p.14013-14017
• Main Authors: Shiga, Takuya, Sato, Yamato, Tachibana, Minami, Sato, Hiroki, Matsumoto, Takuto, Sagayama, Hajime, Kumai, Reiji, Murakami, Youichi, Newton, Graham N, Oshio, Hiroki
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.8b01856

Two carboxyl-substituted iron­(II) grids, one protonated, [Fe4(HL)4]­(BF4)4·4MeCN·AcOEt (1), and the other deprotonated, [Fe4(L)4]·DMSO·EtOH (2), where H2L = 4-{4,5-bis­[6-(3,5-dimethylpyrazol-1-yl)­pyrid-2-yl]-1H-imidazol-2-yl}­benzoic acid, were synthesized. Single-crystal X-ray structure analyses reveal that both complexes have a tetranuclear [2 × 2] grid structure. 1 formed one-dimensional chains through intermolecular hydrogen bonds between the carboxylic acid units of neighboring grids, while 2 formed two-dimensional layers stabilized by π–π-stacking interactions. 1 showed spin transition between the 3HS-1LS and 1.5HS-2.5LS states around 200 K, while 2 showed spin-crossover between the 4LS and 2LS-2HS states above 300 K. A modified indium–tin oxide (ITO) electrode was fabricated by soaking the ITO in a solution of 1. The resultant electrode showed reversible redox waves attributed to the original redox processes of iron­(II)/iron­(III).