Modeling Optical and Photochemical Properties of Biomedical Imaging Dyes

Abstract

This dissertation focuses on modeling optical and photochemical properties of biomedical imaging dyes. Specifically, two optical imaging systems are examined: optoacoustic and chemiluminescent dyes. The first chapter provides motivation and background information for these particular modalities, as well as a brief discussion of the computational approachesemployed. The second chapter presents a computational study of squaraine dyes to facilitate an understanding of how structural features influence optoacoustic signal generation. The specific foci of this investigation are two features most relevant to optoacoustic signal generation: absorption and non-radiative relaxation. This work highlights how minor substituent modifications have a substantial impact on absorption properties and explain these effects via analysis of frontier molecular orbitals (MOs). In addition, the role of structural flexibility is examined and a path for further work in this area is described.The last two chapters focus on separate processes contributing to chemiluminescence in imidazopyrazinone dyes. The third chapter presents a computational modeling of ground state reactions that precede chemiexcitation, namely how different substituents affect the formation of a necessary dioxetanone intermediate. The fourth and final chapter focuses on the dioxetanone decomposition that produces the final excited state intermediate, as well as the emission wavelength of this product. Here we examine the relationship between substituent groups and frontier MO energies and present preliminary results for modeling the S0/S1 conical intersection. This work demonstrates the interplay between multiple aspects of probe development, with a key insight into how modifications that produce desired emission wavelengths may result in higher energy barriers for chemiluminescent activation.