Reversible on-off switching of spin-crossover behavior via photochemical [2+2] cycloaddition reaction  

作　　者：Long-Fei Wang Bang-Heng Lv Feng-Tai Wu Guo-Zhang Huang Ze-Yu Ruan Yan-Cong Chen Min Liu Zhao-Ping Ni Ming-Liang Tong 

机构地区：[1]Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education,School of Chemistry,Sun Yat-Sen University,Guangzhou 510006,China [2]School of Nuclear Science and Technology,University of South China,Hengyang 421001,China

出　　处：《Science China Chemistry》2022年第1期120-127,共8页中国科学（化学英文版）

基　　金：supported by the National Key Research and Development Program of China(2018YFA0306001);the Nas tional Natural Sciences Foundation of China(21773316,21801258,21821003);the Pearl River Talent Plan of Guangdong(2017BT01C161)。

摘　　要：Herein,we report the first example showing the reversible on-off switching of spin-crossover(SCO)property by solid state photochemical[2+2]reaction.The ultraviolet(UV)light-induced[2+2]cycloaddition reaction of 3-spy ligands in a twodimensional(2D)Hofmann-type framework[Fe(3-spy)_(2){Pd(CN)_(4)}](1,3-spy=3-styrylpyridine),which shows a hysteretic twostep SCO behavior,gives a 3D Hofmann-type framework[Fe(rctt-3-ppcb){Pd(CN)_(4)}](2,rctt-3-ppcb=rctt-1,3-bis(3-pyridyl)-2,4-bis(phenyl)cyclobutane,r=reference group,c=cis and t=trans)accompanied with the disappearing of SCO properties.Moreover,upon heating at 250℃ for 12 h,the rctt-3-ppcb ligand in 2 could be partially dedimerized to 3-spy with 68%completion through single-crystal-to-single-crystal(SCSC)transformation,giving the annealing complexes[Fe(3-spy)1.36(rctt-3-ppcb)0.32{Pd(CN)_(4)}](3)which display an incomplete SCO behavior.The 2■3 interconversion is successfully achieved via continuous UV irradiation and thermal annealing,demonstrating the effectiveness of photochemical[2+2]reaction on switching on-off SCO properties.

关 键 词：reversible photo cycloaddition SPIN-CROSSOVER Hofmann-type frameworks PHOTOMAGNETISM 

分 类 号：O621.25[理学—有机化学]