Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

Keishiro Tahara; Tetsufumi Nakakita; Alyona A Starikova; Takashi Ikeda; Masaaki Abe; Jun-Ichi Kikuchi

doi:10.3762/bjoc.15.220

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

Beilstein J Org Chem. 2019 Sep 24:15:2277-2286. doi: 10.3762/bjoc.15.220. eCollection 2019.

Authors

Keishiro Tahara^{1

2}, Tetsufumi Nakakita², Alyona A Starikova³, Takashi Ikeda¹, Masaaki Abe¹, Jun-Ichi Kikuchi²

Affiliations

¹ Department of Material Science, Graduate School of Material Science, University of Hyogo, 3-2-1, Kouto, Kamigori, Ako, Hyogo 678-1297, Japan.
² Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5, Takayama, Ikoma, Nara 630-0192, Japan.
³ Institute of Physical and Organic Chemistry, Southern Federal University, pr. Stachki 194/2, Rostov on Don, 344090, Russian Federation.

Abstract

We report the synthesis of a new bistriarylamine series having a urea bridge and investigate its mixed-valence (MV) states by electrochemical and spectroelectrochemical methods. We found that the supporting electrolytes had unusual effects on potential splitting during electrochemical behavior, in which a smaller counteranion thermodynamically stabilized a MV cation more substantially than did a bulky one. The effects contrary to those reported in conventional MV systems were explained by zwitterionization through hydrogen bonding between the urea bridge and the counteranions, increasing the electronic interactions between two triarylamino units. Furthermore, we clarified the intervalence charge transfer characteristics of the zwitterionic MV state.

Keywords: anion binding; electrochemistry; hydrogen bonding; triarylamine; urea; zwitterionic mixed valency.