Synthesis And Properties Of Boron-containing Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbon systems(PAHs),can be regarded as graphene fragment molecules,which have attracted tremendous attention in the field of chemistry and materials.Among them,non-KekuléPAHs,possess unique electronic structure and physical properties,therefore,they are viewed as promising organic materials.These non-Kekulépolycyclic molecules,consist of an odd number of conjugated carbon atoms and an odd number of?electrons,and leave one unpaired electron highly delocalized in the molecular framework.They are ready to accpet or lose an electron,resulting in the corresponding anion and cationic.Due to the special redox properties of phenalenyl/olympicenyl radical,together with intriguing electromagnetic properties,they are important building blocks to construct organic materials.However,the unpaired electron in such non-Kekulébenzenoid,is mainly delocalized along the zigzag edges rather than the core,resulting in inherently high reactivity of outer rims.This greatly limits their extensive research and further applications.To modify the electronic structure and physical property of PAHs,incorporating an sp~2 hybrid boron atom(ie,trivalent boron)into?-system,is an effective method to significantly reduce the HOMO energy levels of the molecules.The sp~2 hybrid boron atom has an empty p-orbital that can form a p-?conjugate,and it is also susceptible to nucleophiles,rendering it highly sensitive to water and oxygen.Therefore,it is challenging to do molecular design and synthesis.For their pratical applications,the important point is to develope new strategies for stable boron-containing heteropolycyclic aromatics.New boron-containing compounds helps us to in-depth understand their intrinsic electronic characteristics and physical properties.In this work,we will report the synthesis and characterizations of boron or boron-nitrogen-boron containing polycyclic aromatic hydrocarbon such as phenalene and olympicene.Our particular interest is to understand how the incorporation of boron-containing moiety affect their electronic structure,physical property and chemical reactivity.The thesis includes four parts as following:1.The boron-nitrogen-boron(two?-electron three-center)unit was embedded into the zigzag edge of phenalenyl,leading to an interesting B-N-B bonded phenalenyl(BNB phenalenyl).Their electronic struture and physical properties were studied accordingly.For these challenging compounds,we should carefully chose the reaction condition to perform a final ring-closure step.These compound exhibited interesting electronic strucure.We found that the B-N-B moiety participates in the?-electron delocalization along the whole DBAP skeleton like their phenalenyl cation counterparts,but with localized character.2.We investigated the electron-accepting ability of boron-containing phenalenyl.Upon accepting one or two electrons,the boron-containing phenalenyl radical anion or dianion formed.The radical anion has weak aromaticity and exhibits unique chemical reactivity,leading to an unexpected re-arrangement product with BNBC2-embedded benzo[c,d]fluoranthene.3.We developed a new method for borylation of alkyne to form boron-doped olympicene.Owing to the aromatic planar structure,the boraolympicenes are remarkably stable,allowing for handling in the presence of air and moisture and further functional modification.The single crystal structure analysis shows that the insertion of the boron atom can introduce intermolecular close contacts,which is beneficial for charge transport.4.By boron-doping at the concave site of zigzag edge,olympicene possesses intriguing properties such as wide-range visible absorption,low-lying LUMO level,as well as closely arranged trimeric?-?stacking to form a 1D cofacial?-column,beneficial for the promising applications in organic devices.The device tests show that the new concave boraxolympicene molecule exhibit rare organic conductor properties,which is the first study of the organic conductor properties of organoboron compounds.Furthermore,upon adding one electron to the?-core of11a-boraolympicene,the radical anion was obtained.Electron paramagnetic resonance,UV-vis-NIR spectroscopy and theoretical calculations show that single electron is highly delocalized in the conjugated?system.