Synthesis And Properties Of Ullazine-Based π Conjugated System

Both of doping with heteroatoms and π-extension have been proven effective in improving the properties of polycyclic aromatic hydrocarbons(PAHs).Heteroatomdoped and π-extended PAHs have found extensive applications in various fields,including biomedicine,transition metal catalysis,and organic optoelectronic materials.Ullazine,a novel nitrogen-doped PAHs,has attracted a lot attention.In this thesis,we focus on the synthesis and properties of ullazine-based π conjugated system and explore the potential application of π-extended ullazines in the field of optoelectronic.In the first part,two π-expanded ullazines,including symmetric(2CC)and asymmetric structures(1CC),as well as their boron-oxygen-doped counterparts 2BO and 1BO,were designed and synthesized.The effects of different size of conjugation and embedded boron-oxygen bonds on the photophysical properties of the π-expanded ullazines were revealed by experimental studies as well as density functional theory calculations.In addition,organic flexible micro/nanolasers were fabricated based on the polyethylene spheres of π-expanded ullazines,and the preliminary results showed that embedding of the boron-oxygen units led to the performance enhancement.In the second part,nanographenes(6US-1 and 6US-2)containing six ullazines was designed,and one of them(6US-1)was synthesized successfully.and Molecular structure and properties of 6US-1 were investigated.Optimized structure of 6US-1shows the saddle-shaped multiple helicene conformation.Although,we could not able to obtain 6US-2 with large conjugation size,the effect of different size of conjugation on the properties of the ullazine-based nanographenes was revealed by the density functional theory calculations.In conclusion,this thesis is focusing on the synthesis and property study of conjugated ullazines,providing new ideas as well as experiments basis for the application of ullazine-based conjugated molecules in the field of optoelectronic materials.