Development of an Iron(II) Complex Exhibiting Thermal- and Photoinduced Double Proton-Transfer-Coupled Spin Transition in a Short Hydrogen Bond
Takumi Nakanishi, Yuta Hori, Yasuteru Shigeta, Hiroyasu Sato, Ryoji Kiyanagi, Koji Munakata, Takashi Ohhara, Atsushi Okazawa, Rintaro Shimada, Akira Sakamoto, Osamu Sato
Abstract
Multiple proton transfer (PT) controllable by external stimuli plays a crucial role in fundamental chemistry, biological activity, and material science. However, in crystalline systems, controlling multiple PT, which results in a distinct protonation state, remains challenging. In this study, we developed a novel tridentate ligand and iron(II) complex with a short hydrogen bond (HB) that exhibits a PT-coupled spin transition (PCST). Single-crystal X-ray and neutron diffraction measurements revealed that the positions of the two protons in the complex can be controlled by temperature and photoirradiation based on the thermal- and photoinduced PCST. The obtained results suggest that designing molecules that form short HBs is a promising approach for developing multiple PT systems in crystals.