The Synthesis And Characterization Of Novel Curved Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons（PAHs）have been extensively investigated in fluorescent molecular probes,supramolecular chemistry,organic electronics and other fields.In particular,twisted polycyclic aromatic hydrocarbons have attracted a great deal of attention due to their unique molecular structures and self-assembly behaviors.However,these compounds are relatively underexplored due to the synthetic challenges that involve the introduction of a certain degree of strain and simultaneously regioselective fusion of many rings.As a result,it is suffering from harsh synthesis conditions,low product yields,and difficulties in separation.Our work focuses on the synthesis of several novel twisted polycyclic aromatic hydrocarbons,and explores their synthesis,assembly and semiconductor properties.The main contents are as following:1.Synthesis ofπ-Expanded triple[5]helicenes bearing dibenzocoronene monoimide subunits.The new p-expanded triple[5]helicenes have been synthesized via the selective bromination,Suzuki coupling reaction,Ni-catalyzed Yamamoto coupling reaction and Scholl reaction.The results show that the compound exhibits different molecular configurations in solvent and C₁distorted configurations in solid state due to its low energy barrier.The UV absorption spectrum,fluorescence emission spectrum and electrochemical properties were tested.The thin film devices were measured under nitrogen,it exhibits ambipolar characteristics with electron and hole mobilities of 1.2×10^-4and 6.8×10^-5cm²V^-1s^-1.2.Synthesis of the bowl-shaped molecule bearing imide groups.Dibenzocene bearing two imide groups has been synthesized via intermolecular D-A reaction and intramolecular Pd-catalyzed ring closure reaction.The synthesis conditions of C₇₀fragment modified by imide group were investigated through the[4+2]cyclization reaction between alkynes and olefin,the intramolecular ring closure reactions.Studies show that imide groups can improve the solubility of the compound and reduce the LUMO level of the molecule.According to the CV measurements,it is found that the molecule has two reversible reduction peaks,with half-wave potentials of-1.07 and-1.35 e V respectively.According to the onset of the CV,LUMO energy level is estimated to be-3.73 e V,which facilitates electron injection.The single crystal mobility of the material can reach 0.12 cm²V^-1s^-1with high stability.3.Synthesis of twisted aromatic hydrocarbons based on cyclodecene.Using monobromo-substituted acenaphthene as raw material,a series of different configurations of helicene molecules and negative curvature polycyclic aromatic hydrocarbons containing seven-membered rings were synthesized by Sonogashira coupling reaction,radical bromination reaction,intermolecular[2+2+2]coupling reaction and Scholl reaction.The UV absorption,cyclic voltammetry and molecular configuration of the compound were studied.4.Synthesis of pyrroroperylene monoimide pyrroroperylene monoimide was synthesized by oxidative dehydrogenation catalyzed by DDQ and sulfone group substitution catalyzed by I₂.It was shown that the the longest wavelength absorption exhibits a large red-shift compared with perylene monoimide.The theoretical calculation shows that the LUMO level of molecules decreases and the HOMO level increases,which leads to the decrease of the band gap of the molecule.The reactivity of the compound with fluorobenzene was further explored.