CO<sub>2</sub>‐Induced Spin‐State Switching at Room Temperature in a Monomeric Cobalt(II) Complex with the Porous Nature
Manabu Nakaya, Wataru Kosaka, Hitoshi Miyasaka, Yuki Komatsumaru, Shogo Kawaguchi, Kunihisa Sugimoto, Yingjie Zhang, Masaaki Nakamura, Leonard F. Lindoy, Shinya Hayami
Abstract
Abstract CO 2 ‐responsive spin‐state conversion between high‐spin (HS) and low‐spin (LS) states at room temperature was achieved in a monomeric cobalt(II) complex. A neutral cobalt(II) complex, [Co II (COO‐terpy) 2 ]⋅4 H 2 O ( 1⋅4 H 2 O ), stably formed cavities generated via π–π stacking motifs and hydrogen bond networks, resulting in the accommodation of four water molecules. Crystalline 1⋅4 H 2 O transformed to solvent‐free 1 without loss of porosity by heating to 420 K. Compound 1 exhibited a selective CO 2 adsorption via a gate‐open type of the structural modification. Furthermore, the HS/LS transition temperature ( T 1/2 ) was able to be tuned by the CO 2 pressure over a wide temperature range. Unlike 1 exhibits the HS state at 290 K, the CO 2 ‐accomodated form 1⊃CO 2 ( P =110 kPa) was stabilized in the LS state at 290 K, probably caused by a chemical pressure effect by CO 2 accommodation, which provides reversible spin‐state conversion by introducing/evacuating CO 2 gas into/from 1 .