CO2 -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

doi:10.1002/anie.202003811

CO₂ -Induced Spin-State Switching at Room Temperature in a Monomeric Cobalt(II) Complex with the Porous Nature

Angew Chem Int Ed Engl. 2020 Jun 22;59(26):10658-10665. doi: 10.1002/anie.202003811. Epub 2020 Apr 8.

Authors

Affiliations

¹ Department of Chemistry, Graduate School of Science and Technology, Kumamoto University, 2-39-1, Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan.
² Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.
³ Diffraction & Scattering Division Japan, Synchrotron Radiation Research Institute (JASRI), 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5198 (, Japan.
⁴ Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW, 2232, Australia.
⁵ School of Chemistry, The University of Sydney, Sydney, NSW, 2006, Australia.
⁶ Institute of Pulsed Power Science (IPPS), Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan.

PMID: 32189464
DOI: 10.1002/anie.202003811

Abstract

CO₂ -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 H₂ O (1⋅4 H₂ 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 H₂ O transformed to solvent-free 1 without loss of porosity by heating to 420 K. Compound 1 exhibited a selective CO₂ 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 CO₂ pressure over a wide temperature range. Unlike 1 exhibits the HS state at 290 K, the CO₂ -accomodated form 1⊃CO₂ (P $_{CO_{2}}$ =110 kPa) was stabilized in the LS state at 290 K, probably caused by a chemical pressure effect by CO₂ accommodation, which provides reversible spin-state conversion by introducing/evacuating CO₂ gas into/from 1.

Keywords: carbon dioxide; cobalt(II) ions; hydrogen bonding; spin-state change; π-π stacking.