三重硫杂扭曲多环芳烃的合成与表征

Synthesis and characterization of a twisted tri-sulfur-doped polycyclic aromatic hydrocarbon

多环芳烃,通常指的是包含两个或两个以上稠和苯环的芳香化合物.多环芳烃具有优良的光、电及组装性能,在有机发光二极管、有机场效应晶体管、有机太阳能光伏电池等领域具有重要的应用前景.在多环芳烃中,杂原子的引入可以调控其电子结构、偶极矩、组装行为等.其中硫杂多环芳烃,由于其在光电转换、有机电子器件方面表现出的优异性质,而被广泛关注.本研究通过对含有3个噻吩环的寡聚苯撑前体,进行氧化脱氢环化,得到了三重硫杂的多环芳烃分子C_(36)S_(3)H_(10)(C_(9)H_(11))_(6).该三重硫杂多环芳烃含有两个五螺烯的结构单元,呈现出扭曲的几何分子结构.扭曲的分子结构阻碍了分子间的π-π堆积,这也通过变浓度的紫外可见吸收光谱表征得以确认.进一步通过荧光及瞬态荧光光谱,对该三重硫杂扭曲多环芳烃的光学特性进行了研究.

Polycyclic aromatic hydrocarbons(PAHs)generally refer to aromatic compounds containing two or more fused benzene rings.PAHs have excellent optical,electronic and self-assembly properties,and have important applications in organic light-emitting diodes(OLED),organic field effect transistors(OFET),organic solar photovoltaic cells(OPVC)and other fields.The introduction of heteroatoms to PAHs can adjust the electronic structure,dipole moment,and the self-assembly behavior.Among them,sulfur-doped PAHs have been widely studied.Due to the proper energy level and bonding mode of sulfur atom,the sulfur-doped PAHs have stronger dipole-dipole interactions,electron donating ability,and weakened aromaticity.Sulfur-doped PAHs usually exhibit unique redox characteristics and better hole transporting,so they are widely used as p-type organic semiconductor and electronic donor in photoelectric conversion,and donation unit in donoracceptor conjugated molecules.Doping PAHs with sulfur is mainly through two ways:post-modification and fusing the sulfur-containing heterocyclic unit.On the other hand,regarding the regulation of geometric structure of carbon skeleton,non-hexagonal ring is introduced to transform the molecular structure from planar to curved structure.The structural distortion can be achieved by the peripherial stereo-hindrance.For example,the PAHs containing helicene units have a highly distorted structure,thus showing a unique optical,electric and assembly properties.In order to construct novel PAHs,this article combines heteroatom doping and geometric control of carbon skeleton.A twisted tri-sulfur-doped PAH C_(36)S_(3)H_(10)(C_(9)H_(11))_(6)(molecule 1)was synthesized by oxidative cyclodehydrogenation of an oligophenylene precursor,which contains three thiophene rings.X-ray single crystal diffraction exactly characterized the structure of molecule 1.Because the ring is not completely fused,molecule 1 contains two[5]helicene units,which leads to a twisted molecular structure.In crystalline state,molecule 1 forms dimers through C-H···πand weakπ-πinteractions,which further packs into one-dimensional columnar stacking through the weak interactions of C-H···πand C-H···S.Different from the planar PAHs,the twisted molecule 1 is not easy to aggregate in solution.Molecule 1 exhibits a yellow photoluminescence,but its quantum yield is low.Combined with the study of transient fluorescence spectroscopy,it is speculated that its twisted molecular structure may be the reason for its low quantum yield.The synthesis of molecule 1 enriches the family of sulfur-doped PAHs,and the derivatives with alkyl chains of molecule 1 can be synthesized in the future and be used as organic semiconductors or electron donors in solar cells and organic electronic devices,etc.