Symmetry-Broken Intermolecular Charge Separation of Cationic Radicals

Guanghua Liu; Lei Gao; Yi Han; Yao Xiao; Bochao Du; Jianye Gong; Jinlian Hu; Fujin Zhang; He Meng; Xiang Li; Xueliang Shi; Zhe Sun; Jianguo Wang; Gaole Dai; Chunyan Chi; Qing Wang

doi:10.1002/anie.202301348

Symmetry-Broken Intermolecular Charge Separation of Cationic Radicals

Angew Chem Int Ed Engl. 2023 Apr 3;62(15):e202301348. doi: 10.1002/anie.202301348. Epub 2023 Mar 3.

Authors

Guanghua Liu¹, Lei Gao¹, Yi Han², Yao Xiao¹, Bochao Du¹, Jianye Gong¹, Jinlian Hu³, Fujin Zhang⁴, He Meng¹, Xiang Li⁵, Xueliang Shi⁶, Zhe Sun³, Jianguo Wang¹, Gaole Dai⁷, Chunyan Chi², Qing Wang¹

Affiliations

¹ School of Chemistry and Chemical Engineering, Inner Mongolia University, 235 West University Street, Hohhot, 010021, China.
² Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore.
³ Institute of Molecular Plus, Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, Tianjin University, 92 Weijin Road, Tianjin, 300072, China.
⁴ Institute of Environmental Resources and Analytical Technique, Inner Mongolia Academy of Agricultural and Animal Husbandry Sciences, Zhao Jun Road, Hohhot, 010031, China.
⁵ Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
⁶ Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China.
⁷ College of Material, Chemistry and Chemical Engineering, Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Hangzhou Normal University, 2318 Yuhangtang Road, Hangzhou, 311121, Zhejiang, China.

PMID: 36792536
DOI: 10.1002/anie.202301348

Abstract

A quadrupolar compound Pyr-BA with two pyrrole-type nitrogen atoms doped externally was prepared in this work. In high contrast with other π ionic radicals, its cationic radical Pyr-BA⋅⁺ undergoes unusual symmetry-broken charge separation (SB-CS), generating the mixed valence complex of Pyr-BA^+1-q ⋅⋅⋅Pyr-BA^+1+q , where q is the degree of charge transfer. Variable-temperature (VT) single-crystal analysis, absorption and EPR experiments all confirmed that aggregation and lower temperature would help to facilitate this SB-CS process. Gibbs energy calculations and gauge-including magnetically induced current simulation both validate that, for Pyr-BA⋅⁺ , SB-CS behavior is more favorable than the conventional dimerization mode. To the best of our knowledge, this is the first study that shows solid single-crystal evidence for spontaneous SB-CS between identical ionic radicals. Such a unique phenomenon is of great significance both in terms of fundamental aspects and uncharted material science.

Keywords: Cationic Radical; Mixed Valence Complex; Nitrogen Doping; Quadrupole; Symmetry Broken Charge Separation.

Abstract

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