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-methanoannulene 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.
Bibliographical noteFunding Information:
This research at Yonsei University supported by the Strategic Research (NRF2016R1E1A1A01943379) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, and related quantum calculations were performed with the supercomputing resources of the Korea Institute of Science and Technology Information. We thank MINECO/FEDER of the Spanish Government (CTQ2015-69391-P and CTQ2016-80955-P) projects and the US National Science Foundation (CHE-1607821). The work at Pusan National University was supported by the National Research Foundation of Korea (NRF) grant funded by the MEST (NRF-2017R1A2A2A05001052).
© 2019, The Author(s).
All Science Journal Classification (ASJC) codes
- Biochemistry, Genetics and Molecular Biology(all)
- Physics and Astronomy(all)