Effects of Different Counter Anions on Solid-State Electron Transfer in Viologen Compounds: Modulation of Color and Piezo- and Photochromic Properties

Qi Sui; Peng Li; Rong Sun; Yu-Hui Fang; Lin Wang; Bing-Wu Wang; En-Qing Gao; Song Gao

doi:10.1021/acs.jpclett.0c02690

Effects of Different Counter Anions on Solid-State Electron Transfer in Viologen Compounds: Modulation of Color and Piezo- and Photochromic Properties

J Phys Chem Lett. 2020 Nov 5;11(21):9282-9288. doi: 10.1021/acs.jpclett.0c02690. Epub 2020 Oct 21.

Authors

Qi Sui^{1

2}, Peng Li², Rong Sun¹, Yu-Hui Fang¹, Lin Wang³, Bing-Wu Wang¹, En-Qing Gao², Song Gao^{1

4}

Affiliations

¹ Beijing National Laboratory for Molecular Science, Beijing Key Laboratory for Magnetoelectric Materials and Devices, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China.
² Shanghai Key Laboratory of Green Chemistry and Chemical Processes, College of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, P. R. China.
³ Center for High Pressure Science (CHiPS), State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao, Hebei 066004, China.
⁴ School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, Guangdong 510640, China.

PMID: 33085492
DOI: 10.1021/acs.jpclett.0c02690

Abstract

Charge transfer (CT) and electron transfer (ET) underlie the various applications of viologen compounds. However, the CT and ET in solids are still insufficiently understood and difficult to control, which is challenging but fundamental to the design of multifunctional materials. Our strategy is to attempt a delicate control of CT and ET by subjecting model compounds to pressure. In this work, a series of viologens of the same cation with different anions show anion-dependent color and piezo-/photochromism due to ground-state CT and stimuli-induced ET; the ease of solid-state ET can be tuned in the order of Cl^- > Br^- > I^-/BF₄^-/PF₆^-/ClO₄^-. With in situ high pressure UV-vis experiments, we also observed unexpectedly the pressure-induced solid-state ET in [H₂bcpV]·I₂ besides the pressure modulation of the CT absorption. It proves pressure is a more powerful stimulus than light in tuning solid-state CT and ET.