Excited-State Aromatic Interactions in the Aggregation-Induced Emission of Molecular Rotors

Jiri Sturala, Marc K. Etherington, Aisha N. Bismillah, Heather F. Higginbotham, William Trewby, Juan A. Aguilar, Elizabeth H. C. Bromley, Alyssa-Jennifer Avestro, Andrew P. Monkman, Paul R. McGonigal

Research output: Contribution to journalArticlepeer-review

72 Citations (Scopus)
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Abstract

Small, apolar aromatic groups, such as phenyl rings, are commonly included in the structures of fluorophores to impart hindered intramolecular rotations, leading to desirable solid-state luminescence properties. However, they are not normally considered to take part in through-space interactions that influence the fluorescent output. Here, we report on the photoluminescence properties of a series of phenyl-ring molecular rotors bearing three, five, six, and seven phenyl groups. The fluorescent emissions from two of the rotors are found to originate, not from the localized excited state as one might expect, but from unanticipated through-space aromatic-dimer states. We demonstrate that these relaxed dimer states can form as a result of intra- or intermolecular interactions across a range of environments in solution and solid samples, including conditions that promote aggregation-induced emission. Computational modeling also suggests that the formation of aromatic-dimer excited states may account for the photophysical properties of a previously reported luminogen. These results imply, therefore, that this is a general phenomenon that should be taken into account when designing and interpreting the fluorescent outputs of luminescent probes and optoelectronic devices based on fluorescent molecular rotors.
Original languageEnglish
Pages (from-to)17882-17889
Number of pages8
JournalJournal of the American Chemical Society
Volume139
Issue number49
Early online date1 Dec 2017
DOIs
Publication statusPublished - 13 Dec 2017
Externally publishedYes

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