Synthesis And Properties Of Stable Z-Acene Biradicals

Polycyclic aromatichydrocarbons(PAHs)as the graphene fragments have received extensive attention in the field of materials science and chemistry.Among PAHs,?-conjugated diradicals with unique electronic structure consisted of two unpaired electrons have potential application in the field of organic light emitting diodes,organic conductor,organic field effect transistor,organic solar cell and nearinfrared dyes due to their unique electronic structure and photoelectromagnetic properties.However,the material applications of diradical compounds remain largely unexplored.The main reasons are listed as below: 1)It is difficult to synthesize and characterize the diradicals due to its poor stability;2)It is difficult to decorate molecular skeleton to extend molecular system.Therefore,it is very important to design and synthesize stable diradical compounds for materials application.In this thesis,a series of novel zethrene derivatives with helical structure were designed and synthesized by kinetic and thermodynamic stabilization strategies.Their single crystal structures and physical properties were investigated.At last,we investigated the effects of helical structure in zethrene derivatives on their chemical and physical properties.The specific research contents are listed as follows:In the second chapter,we synthesized a series of 5,6:12,13-dinaphthozethrene diradical derivatives,which showed a small HOMO-LUMO energy gap,compact molecular interaction and reversible redox properties.Meanwhile,theoretical calculations and experimental results indicated those compounds are diradicaloid species,and both the open-shell resonance structure and close-shell resonance structure contributed to the electronic ground state.The toluene solution of 5,6:12,13-dinaphthozethrene derivative under ambient and light condition showed a half-life times of 30 days,demonstrating its high stability.The optical properties were investigated by absorption spectra and fluorescence spectra.In addition,the X-ray crystallographic analysis indicated there are two enantiomers of(P,P)and(M,M)in single crystal and their isomerization process was also investigated by DFT calculation.In the third chapter,we designed and synthesized a novel diradicaloid of 5,6:12,13-diphenanthzethrene derivative with bi-[5]-helicene structures at first,which showed a good stability.Then we investigated its geometry structure,electronic structure and aromaticity combined with experimental characterization and theoretical calculation.In addition,we also investigated the effect of helical structure on physicochemical properties of diradicaloid.The compound showed a strong absorption band at 643 nm and a strong emission band at 660 nm.