Cation modulated spin state and near room temperature transition within a family of compounds containing the same [FeL2]2- center

Jia-Hui Liu; Xiao-Qing Guo; Zi-Cheng Wang; Li-Xuan Cai; Li-Peng Zhou; Chong-Bin Tian; Qing-Fu Sun

doi:10.1039/d1dt04254h

Cation modulated spin state and near room temperature transition within a family of compounds containing the same [FeL₂]^2- center

Dalton Trans. 2022 Mar 8;51(10):3894-3901. doi: 10.1039/d1dt04254h.

Authors

Jia-Hui Liu^{1

2}, Xiao-Qing Guo², Zi-Cheng Wang^{1

2}, Li-Xuan Cai², Li-Peng Zhou², Chong-Bin Tian^{1

2}, Qing-Fu Sun^{1

2}

Affiliations

¹ College of Chemistry and Materials Science, Fujian Normal University, Fuzhou 350007, China. tianchongbin@fjirsm.ac.cn.
² State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China.

PMID: 35167636
DOI: 10.1039/d1dt04254h

Abstract

Spin-crossover (SCO) active compounds have received much attention due to their potential application in molecular devices. Herein, a family of solvent-free Fe^II compounds, formulated as (A)₂[FeL₂], (H₂L = pyridine-2,6-bi-tetrazolate, A = (Me)₄N⁺1, Et₂NH₂⁺2, ⁱPr₂NH₂⁺3 and ⁱPrNH₃⁺4), were synthesized and characterized. Single-crystal X-ray diffraction studies reveal that 1-4 are all supramolecular frameworks containing the same [FeL₂]^2- center, which is arranged into two packing modes via inter-molecular interactions, that is, a 3D architecture in 1 and 1D chain in 2-4. The spin states of 1-4 at different temperatures are assigned on the basis of the single-crystal X-ray diffraction data. Solid state magnetic investigations indicate that 1 and 4 exhibit a low spin state (below 350 K) and high spin state (2-400 K), respectively. 2 and 3 display clear SCO behavior in the measured temperature, but with different profiles and critical temperatures. 2 undergoes a complete gradual SCO with a critical temperature of T_1/2 = 260 K. 3 has an abrupt near room temperature transition between T_{1/2 cooling} = 278 K and T_{1/2 warming} = 286, centered at 282 K (9 °C). This study reveals the importance of organic cations in the modulation of SCO behavior and offers a new insight for the design of SCO compounds with near room temperature spin transitions.