Design, Synthesis And Photoelectric Properties Of Sulfur And Nitrogen Doped Cyclic Conjugated Molecules

Organic conjugated molecules,as emerging optoelectronic materials,have attracted extensive attention due to their ease of preparation,solution processability,and adjustable properties.The development of molecules with novel structures and excellent properties is of great importance.Cyclic conjugated molecules possess radialπ-conjugated and curvedπ-planes,which are promising candidates in the field of organic optoelectronic materials.Cycloparaphenylenes（CPPs）can be used as the smallest building blocks of armchair-type carbon nanotubes,and have excellent optoelectronic properties.They are currently one of the most representative cyclic conjugated molecules.However,the precise modulation of the optoelectronic properties of CPPs-like molecules is an essential and difficult issue in this research field.Based on this,in order to obtain CPPs derivatives with specific sizes and superior properties,this thesis adopted a bottom-up synthesis strategy to introduce heterocycles into CPPs,and prepare multiple heterocycle-doped CPPs of different sizes.Furthermore,the basic optoelectronic properties and potential application prospects of CPPs molecules were explored.The details are as follows:（1）In this chapter,thiophene units with different attachment sites were selected as the building blocks of CPPs.Four different CPPs derivatives containing thiophene units were designed by changing the molecular size.After selecting the appropriate reaction intermediate,the cyclic precursor was obtained through the Suzuki-Miyaura coupling reaction,and H₂Sn Cl₄ was then used in reductive aromatization reaction to successfully synthesize the target products 2,5-T[10]CPP and 3,4-T[9]CPP.The structure and properties of the two products were confirmed by a series of characterization methods.The results demonstrated that the conjugation degree of compound 3,4-T[9]CPP was lower than compound 2,5-T[10]CPP,but it showed a higher fluorescence quantum yield（0.65）.It shows that the introduction of 3 and 4-position thiophene units into the molecule can break the high symmetry of molecular orbitals of CPPs molecules,which can effectively improve the fluorescence quantum yield of the compounds.（2）In this chapter,we select sulfur and nitrogen doped fluorene derivatives as building blocks to design and synthesize compounds Bu₂-F[8]CPP,DBT[8]CPP,Me-CZ[8]CPP and EH-CZ[8]CPP,and the molecular structures were further confirmed.The photophysical properties of the target product were studied.The symmetry of the four target molecules was broken and the fluorescence quantum yields were significantly improved compared with the compound 3,4-T[9]CPP.Among them,the fluorescence quantum yield of the sulfur-doped compound DBT[8]CPP reaches 0.85.Comparing the fluorescence quantum yields of the four compounds,it is shown that heteroatom doping does not necessarily improve the fluorescence quantum yields of CPPs compound.The compound EH-CZ[8]CPP does not have intermolecular interaction force with PC₇₁BM,indicating that size matching plays a decisive role in the inclusion of PC₇₁BM by CPPs when compared with electrostatic interaction.