Two-electron transfer stabilized by excited-state aromatization

Jinseok Kim; Juwon Oh; Seongchul Park; Jose L Zafra; Justin R DeFrancisco; David Casanova; Manho Lim; John D Tovar; Juan Casado; Dongho Kim

doi:10.1038/s41467-019-12986-w

Two-electron transfer stabilized by excited-state aromatization

Nat Commun. 2019 Nov 1;10(1):4983. doi: 10.1038/s41467-019-12986-w.

Authors

Jinseok Kim¹, Juwon Oh¹, Seongchul Park², Jose L Zafra³, Justin R DeFrancisco⁴, David Casanova⁵, Manho Lim⁶, John D Tovar⁷, Juan Casado⁸, Dongho Kim⁹

Affiliations

¹ Spectroscopy Laboratory for Functional π-electronic Systems and Department of Chemistry, Yonsei University, Seoul, 03722, Korea.
² Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan, 46241, Korea.
³ Department of Physical Chemistry, University of Málaga, Andalucia-Tech, Campus de Teatinos s/n, 29071, Málaga, Spain.
⁴ Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218, USA.
⁵ Donostia, International Physics Center (DIPC) & IKERBASQUE - Basque Foundation for Science, Paseo Manuel de Lardizabal, 4, 20018, Donostia-San Sebastián, Euskadi, Spain. david.casanova@ehu.eus.
⁶ Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan, 46241, Korea. mhlim@pusan.ac.kr.
⁷ Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218, USA. jtovar1@jhu.edu.
⁸ Department of Physical Chemistry, University of Málaga, Andalucia-Tech, Campus de Teatinos s/n, 29071, Málaga, Spain. casado@uma.es.
⁹ Spectroscopy Laboratory for Functional π-electronic Systems and Department of Chemistry, Yonsei University, Seoul, 03722, Korea. dongho@yonsei.ac.kr.

Abstract

The scientific significance of excited-state aromaticity concerns with the elucidation of processes and properties in the excited states. Here, we focus on TMTQ, an oligomer composed of a central 1,6-methano[10]annulene and 5-dicyanomethyl-thiophene peripheries (acceptor-donor-acceptor system), and investigate a two-electron transfer process dominantly stabilized by an aromatization in the low-energy lying excited state. Our spectroscopic measurements quantitatively observe the shift of two π-electrons between donor and acceptors. It is revealed that this two-electron transfer process accompanies the excited-state aromatization, producing a Baird aromatic 8π core annulene in TMTQ. Biradical character on each terminal dicyanomethylene group of TMTQ allows a pseudo triplet-like configuration on the 8π core annulene with multiexcitonic nature, which stabilizes the energetically unfavorable two-charge separated state by the formation of Baird aromatic core annulene. This finding provides a comprehensive understanding of the role of excited-state aromaticity and insight to designing functional photoactive materials.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, Non-U.S. Gov't