Date of Completion

2021

Thesis Type

College of Arts and Science Honors

Department

Chemistry

First Advisor

Matthew D. Liptak

Keywords

Aggregation-Induced Emission, Fluorescence, Stokes Shift, Density Functional Theory

Abstract

As interests in applications of small organic fluorophores grow, so does the importance of thoroughly understanding the mechanisms behind photophysical phenomena. The advents of fluorescent probes, organic solar cells, and organic optoelectronic devices motivate research into such phenomena as aggregation-induced emission (AIE) and mega-Stokes shifts. The exhibition of AIE is crucial to the application of fluorophores in solid-state electronics, and large Stokes shifts are key to the efficiency of fluorophores in nearly all applications.

AIE was investigated through a recently proposed mechanism, the Suppression of Kasha’s Rule (SOKR), and its potential exhibition in 1,6-diphenyl-1,3,5-hexatriene (DPH). SOKR explains anomalous fluorescence with a mechanism that simultaneously induces AIE. This connection has immense potential for developing a new class of AIE-gens from anomalous fluorophores. The photophysics of DPH were explored spectroscopically to determine that DPH does not exhibit SOKR. This result led to the proposition of future experiments that could provide more insight into the SOKR mechanism.

Mega-Stokes shifts were investigated through computational modeling of the mega-Stokes shifts exhibited by [1,2,3]triazolo[1,5-a]pyridinium (TOP) and [1,2,3]triazolo[1,5-a]quinolinium (TOQ) dyes. A mechanism was proposed by paired analysis of BLYP- and ωB97-based models. The mechanism relies on the charge-transfer character of absorbance forcing rotation, twist, and bond deformation in excited state structure. Relaxation from the new geometry produces the unusually large Stokes shifts.

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