Document Type

Dissertation

Degree

Doctor of Philosophy

Major

Chemistry, Biochemistry

Date of Defense

6-30-2022

Graduate Advisor

Cynthia M. Dupureur

Committee

Cynthia M. Dupureur

Janet B. Braddock-Wilking

Keith J. Stine

Michael R. Nichols

Abstract

2,7-disubstituted silafluorenes and germafluorenes, originally designed for OLED applications, are a class of fluorescent dyes that have gained recent interest as probes for bioimaging and as biosensors to monitor cellular dynamics and interactions. Desirable biological probes absorb in the visible region, have high extinction coefficients, high quantum yield and excellent photostability. Here, their spectral properties are investigated under aqueous conditions for relevant biological applications. These molecules display intense blue fluorescence in the solid state and in solution, have high extinction coefficients, and exhibit appreciable solubility in aqueous solution. To better understand potential applications, the mechanism of fluorescence was investigated. It was demonstrated that these compounds are sensitive to solvent polarity through intramolecular charge transfer (ICT) and have desirable Stokes shifts in various solvents, up to 60 nm. Density functional theory (DFT) was utilized to screen a library of potential metallafluorenes to find molecules with enhanced sensitivity to solvent polarity. Selected metallafluorenes were then synthesized for further study. This work indicates that 2,7-disubstituted sila- and germafluorenes have excellent potential as biological probes, with the potential to tune the solvatochromism via the 2,7-substituent, and can be efficiently designed using DFT to improve ICT properties.

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