Synthesis, Characterization, and Theoretical Studies of Fluorescent GUMBOS and NanoGUMBOS

Abstract

In this dissertation, novel fluorescent materials, which are referred to as a group of uniform materials based on organic salts (GUMBOS) are synthesized, characterized, and studied for different applications. GUMBOS are solid state organic salts having melting points from 25°C to 250°C. Similar to ionic liquids, GUMBOS are highly tunable and can be designed for specific applications by incorporating multiple-functions into a single ion pair by selection of cation-anion combinations. Chapter 2 is a discussion of the synthesis and characterization of a PEGylated IR786 GUMBOS. These GUMBOS are prepared by a two-step synthesis procedure followed by a facile anion exchange approach. These GUMBOS were found to form nano- and meso-scale GUMBOS in aqueous solution via self-assembly. Optical properties of nano- and meso-scale GUMBOS were investigated and results indicate that anions, such as NTf2 and AOT, play a significant role in improving the photostability of PEG786 GUMBOS. In addition, these nano- and meso-scale GUMBOS resist nonspecific binding to proteins. PEGylation of the original IR786 leads to reduced cytotoxicity. Chapter 3 is a discussion of preparation and characterization of multifunctional ionic liquid crystals composed of (-)-N-Methylephedrine ((-)MeEph) based cation and dysprosium based anion. The cation is obtained by covalently linking an alkyl chain to the nitrogen of (-)MeEph and the anion is a complex consisting of Dy3+ and SCN-1. The (-)MeEph based cation provides the compounds with mesomorphic and chiral properties, and the anion affords paramagnetism and luminescence. These compounds are found to exhibit enhanced luminescence intensities in a liquid crystalline state. In chapter 4, theoretical studies of carbazole-imidazolium based GUMBOS are performed to investigate the electronic and photophysical properties. In particular, Density Functional Theory (DFT) is used to optimize the geometry of these GUMBOS at ground state, while Time Dependent Density Functional Theory (TDDFT) is used to calculate the optical properties of GUMBOS. Studies demonstrate that anions play an important role in determining the geometries of GUMBOS, and in turn affect the HOMO and LUMO configurations as well as electronic and optical properties.