Balancing Charge Transfer and Frenkel Exciton Coupling Leads to Excimer Formation in Molecular Dimers: Implications for Singlet Fission

Youn Jue Bae, Daiki Shimizu, Jonathan D. Schultz, Gyeongwon Kang, Jiawang Zhou, George C Schatz, Atsuhiro Osuka, Michael R. Wasielewski

Research output: Contribution to journalArticlepeer-review

Abstract

Photoexcitation of molecular chromophore aggregates can form excimer states that play a significant role in photophysical processes such as charge and energy transfer as well as singlet fission. An excimer state is commonly defined as a superposition of Frenkel exciton and charge transfer states. In this work, we investigate the dynamics of excimer formation and decay in π-stacked 9,10-bis(phenylethynyl)anthracene (BPEA) covalent dimers appended to a xanthene spacer, where the electronic coupling between the two BPEA molecules is adjusted by changing their longitudinal molecular slip distances. Using exciton coupling calculations, we quantify the relative contributions of Frenkel excitons and charge transfer states and find that there is an upper and lower threshold of the charge transfer contribution for efficient excimer formation to occur. Knowing these thresholds can aid the design of molecular aggregates that optimize singlet fission.

Original languageEnglish
Pages (from-to)8478-8487
Number of pages10
JournalThe journal of physical chemistry. A
Volume124
Issue number41
DOIs
Publication statusPublished - Oct 15 2020

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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