Donor-Donor'-Acceptor Triads Based on [3.3]Paracyclophane with a 1,4-Dithiafulvene Donor and a Cyanomethylene Acceptor: Synthesis, Structure, and Electrochemical and Photophysical Properties

Katsuya Sako; Tomoya Hasegawa; Hiroyuki Onda; Michito Shiotsuka; Motonori Watanabe; Teruo Shinmyozu; Sachiko Tojo; Mamoru Fujitsuka; Tetsuro Majima; Yasukazu Hirao; Takashi Kubo; Tetsuo Iwanaga; Shinji Toyota; Hiroyuki Takemura

doi:10.1002/chem.201801774

Donor-Donor'-Acceptor Triads Based on [3.3]Paracyclophane with a 1,4-Dithiafulvene Donor and a Cyanomethylene Acceptor: Synthesis, Structure, and Electrochemical and Photophysical Properties

Chemistry. 2018 Aug 6;24(44):11407-11416. doi: 10.1002/chem.201801774. Epub 2018 Jul 6.

Authors

Affiliations

¹ Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, 466-8555, Japan.
² International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan.
³ Department of Chemistry, National (Taiwan) University, No. 1, Section 4, Roosevelt Rd, Taipei, 10617, Taiwan.
⁴ The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka, 567-0047, Japan.
⁵ Department of Chemistry, Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka, 560-0043, Japan.
⁶ Department of Chemistry, Faculty of Science, Okayama University of Science, Ridaicho 1-1, Kita-ku, Okayama, 700-0005, Japan.
⁷ Department of Chemistry, School of Science, Tokyo Institute of Technology, Ookayama 2-12-1, Meguro-ku, Tokyo, 152-8550, Japan.
⁸ Department of Chemical and Biological Science, Faculty of Science, Japan Women's University, Mejirodai 2-8-1, Bunkyo-ku, Tokyo, 112-8681, Japan.

PMID: 29845675
DOI: 10.1002/chem.201801774

Abstract

Donor-donor'-acceptor triads (1, 2), based on [3.3]paracyclophane ([3.3]PCP) as a bridge, with electron-donating properties (D') using 1,4-dithiafulvene (DTF; TTF half unit) as a donor and dicyanomethylene (DCM; TCNE half unit) or an ethoxycarbonyl-cyanomethylene (ECM) as an acceptor were designed and synthesized. The pulse radiolysis study of 1 a in 1,2-dichloroethane allowed the clear assignment of the absorption bands of the DTF radical cation (1 a^.+ ), whereas the absorption bands due to the DCM radical anion could not be observed by γ-ray radiolysis in 2-methyltetrahydrofuran rigid glass at 77 K. Electrochemical oxidation of 1 a first generates the DTF radical cation (1 a^.+ ), the absorption bands of which are in agreement with those observed by a pulse radiolysis study, followed by dication (1 a²⁺ ). The ESR spectrum of 1 a^.+ showed a symmetrical signal with fine structure and an ESR simulation predicted that the spin of 1 a^.+ is delocalized over S and C atoms of the DTF moiety and the central C atom of the trimethylene bridge bearing the DTF moiety. Pulse radiolysis, ESR, and electrochemical studies indicate that the DTF radical cation of 1 a^.+ is more stable than that of 6^.+ , and the latter shows a strong tendency to dimerize. This result indicates that the [3.3]PCP moiety as a bridge can stabilize the DTF radical cation more than the 1,3-diphenylpropane moiety because of kinetic stability due to its rigid structure and the weak electronic interaction of DTF and DCM moieties through [3.3]PCP.

Keywords: dithiafulvenes; donor-acceptor systems; paracyclophane; radical cations; triads.