Theses and Dissertations

ORCID

https://orcid.org/0000-0002-7829-733X

Advisor

Gwaltney, Steven R.

Committee Member

Patrick, Amanda L.

Committee Member

Mlsna, Todd E.

Committee Member

Fitzkee, Nicholas C.

Committee Member

Wipf, David O.

Date of Degree

5-16-2025

Original embargo terms

Visible MSU Only 1 year

Document Type

Dissertation - Campus Access Only

Major

Chemistry

Degree Name

Doctor of Philosophy (Ph.D.)

College

College of Arts and Sciences

Department

Department of Chemistry

Abstract

Fluorene-based fluorescing conjugated polymers are being used to develop sensors that show great sensitivity and selectivity, however, important questions about the photophysics of these systems remain unanswered. For example, a fluorescence intensity difference was observed between fluorene dimers linked with either an acetylene (diFA) or phenyl (diFP). The polymers diFA and diFP have similar structures and extinction coefficients, yet diFA yielded a five times higher fluorescence intensity than diFP. In project one, Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) were used to calculate the ground and excited states of diFA and diFP. A python code was developed to solve the 1D hindered rotor Schrödinger equation to determine the Franck-Condon Factors and Boltzmann populations to create theoretical absorbance and fluorescence spectra. It was found that the higher fluorescence of diFA results from excellent FCF overlap that encourages radiative relaxation compared to the poor FCF overlap of the diFP which results in higher non-radiative relaxation. In project 2, the potential of fluorescent tuning with regard to the Hammett number of possible substituents was investigated for the diFA and diFP dimers. DFT and TD-DFT were used to calculate the ground and excited states of the two dimers with 16 different substituents, each added in either the ortho or meta position and taking into consideration the position of the substituents in regard to the linker. Results indicate that Hammett number does not provide an effective measure for fluorescence tuning. However, substituent orientation sometimes did impact excitation energy.

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