Crystal structure characterization of some π-conjugated ionic crystals toward electronic applications

Abstract

Although there are several merits to use organic ionic salts as functional materials, crystal structures of these salts have not been systematically investigated. We synthesized a series of styrylpyridinium and styrylquinolinium with iodide, p-toluenesulfonate, 1-pyrenesulfonate or tetraphenylborate, and their single crystals for X-ray crystallographic analysis were grown. Consequently, 11 crystal structures, based on three iodides, one p-toluenesulfonate, three 1-pyrenesulfonates and one tetraphenylborate, including solvated ones and polymorphs were analyzed. Cation stacking structures were able to be classified into three types, and two structures without cation stacking were also found. Although the HOMO levels of the anions were found to be higher than the LUMO levels of the cations by the DFT calculation, apparent evidence on the electron transfer was not detected. One of the plausible reasons is lack of face-to-face overlapping between cations and anions in the crystal structures.

Keywords:

• Crystal structure
• electron transfer
• organic salt

Acknowledgments

Theoretical calculations were performed at Research Center for Computational Science, Okazaki, Japan. The synchrotron radiation experiments were performed at BL02B1 (2018B1714, 2019A1704) in SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) with the supports by Dr. Kunihisa Sugimoto, JASRI/SPring-8, and Mr. Kei Mizuguchi, Yamagata University.

Additional information

Funding

This work was partially supported by Advanced Next Generation Energy Leadership (ANGEL) project of Japan Society for the Promotion of Science (JSPS).