Excitonic Coupling in Fluorene-Based Bichromophoric Systems: Vibrational Quenching and the Transition from Weak to Intermediate Coupling

Authors

Damian L. Kokkin, Marquette UniversityFollow
Neil Reilly, University of Massachusetts Boston
Maxim V. Ivanov, Amgen Inc.
Rajendra Rathore, Marquette University
Scott A. Reid, Marquette UniversityFollow

Document Type

Article

Publication Date

2023

Publisher

American Chemical Society

Source Publication

Journal of Physical Chemistry A

Source ISSN

1089-5639

Original Item ID

DOI: 10.1021/acs.jpca.3c03511

Abstract

Excimeric systems (i.e., excited dimers) have well served as model compounds for the study of the delocalization of electronic energy over weakly interacting chromophores. However, there remain relatively few isolated systems in which such interactions can be studied experimentally at a level to afford detailed comparisons with theory. In this Article, we examine a series of covalently and noncovalently linked dimers of fluorene, as a model aromatic chromophore, where the formation of excimers requires a π-stacked, cofacial orientation at van der Waals contact. Building upon a series of seminal prior studies that examined vibronic quenching of the excitation interaction in van der Waals dimers, the key question that we sought to address here is whether a single quenching factor could reproduce experimental excitonic splittings across a series of covalently and noncovalently linked bichromophoric systems built from the same chromophore. In comparing experimentally measured excitonic splittings with calculated static splittings using time-dependent density functional methods, we find that all systems save one fall on a line with a slope of 0.080(8), reflecting a vibrational quenching of roughly 1 order of magnitude. The outlier, which shows a significantly reduced quenching factor, represents a cyclophane-linked system where the fluorene moieties are constrained in a cofacial arrangement. We argue that this system evidences the transition from the weak to intermediate coupling regime.

Comments

Accepted version. Journal of Physical Chemistry A, Vol. 127, No. 34 (2023): 7198-7204. DOI. © 2023 American Chemical Society. Used with permission.

Recommended Citation

Kokkin, Damian L.; Reilly, Neil; Ivanov, Maxim V.; Rathore, Rajendra; and Reid, Scott A., "Excitonic Coupling in Fluorene-Based Bichromophoric Systems: Vibrational Quenching and the Transition from Weak to Intermediate Coupling" (2023). Chemistry Faculty Research and Publications. 1066.
https://epublications.marquette.edu/chem_fac/1066