Date

2022-7-1

Author

Çalışgan Ünay, Gizem

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The helical structure is one of the most distinguished motifs encountered at various scales in nature, from subatomic to galactic scale. In the cosmos, as the size reaches a macro level, functionality increases, and the structures become more ordered. In such systems, helicity is commonly observed and plays a crucial role in functionality. With this in mind, helicity at a molecular level is also found intriguing. To form helical structures, small chiral building blocks arrange themselves accordingly with the help of external factors such as solvation. Inspired by these features, novel chiral polymers with modified tartaric acid moiety in the backbone have been designed in this thesis study. For further characterization of the ordered structures, possibly formed by intramolecular interactions and solvent effect, chromophoric units, either squaraine or diaminoterephthalate, were introduced to the polymer backbone during the condensation polymerization. Besides the polymeric level studies, both enantiomeric forms of small chiral squaraine dye-containing compounds were developed and characterized. Furthermore, other than chiral counterparts, three novel squaraine dyes were synthesized. Studies on optical properties, chirality induction, and solvent effects have been carried out using these various-sized compounds. After the synthesis and characterization, small chiral squaraine dye-containing compounds were subjected to aggregation studies in different solvent mixtures. CD activity was observed in the same sense for the aggregates of both D and L-modified alanine dyes. From these results, it was found that the aggregation starts from core squaraine units, and the aggregates of both enantiomers arrange themselves in the most stable form by the same sense positioning. The results were supported by theoretical calculations. In the case of chiral squaraine-containing polymers, the results obtained from CD spectroscopy showed that the helical assemblies were formed during aggregation studies, and the sense of helicity could be controlled by the chirality of the tartaric acid unit. The diaminoterephthale (DAT) containing polymers showed CD activity in single solvents because of their chiroptical features. For the further investigation of DAT chromophores, a model monomer was synthesized and characterized. The results obtained from optical studies of model monomer were consistent with the polymers. It was also found that storage conditions affected the behavior of the DATs in solutions. Theoretical calculations revealed that the H-bonding is essential in their arrangement in solution. The details of synthetic, spectroscopic, chromatographic, and theoretical studies were covered in the following parts of the dissertation.

Subject Keywords

Tartaric acid, CD spectroscopy, Helical structures, Aggregation, Squaraines, Diaminoterephthalate Chromophores

URI

https://hdl.handle.net/11511/98167

Collections

Graduate School of Natural and Applied Sciences, Thesis