Studies On The Synthesis And Optoelectronic Properties Of Benzophospholes And Their Derivatives

Benzo[b]phosphole derivatives,the phosphorous analogue of indole,have unique physical and photoelectric properties,and have been widely used in the field of organic materials science,therefore they draw increasing attention.Pyrrole is aromatic and has electron-donating property,but,phosphole is very weak aromatic and exhibits a feeble electron-withdrawing character.In the phosphole,the central tricoordinate phosphorus atom adopts a pyramidal geometry,the lone pair on the phosphorus center cannot interact with butadiene ?-electrons efficiently,accordingly,the overall aromatic character of this system is reduced intensely,leads to a very low aromaticity of phosphole.Meanwhile,effective orbital interaction happens between the ?* orbital of an exocyclic single bond on the phosphorus atom and the ?* orbital of a butadiene moiety,resulting in a low-lying LUMO energy level of phosphole,means the phosphole ring has a certain degree of electron-accepting and electron-transporting ability.In addition,phosphole retains a diverse reactivity of the central phosphorus atom,and this makes it possible tune the properties by using simple chemical modifications,such as oxidation,sulfidation,alkylation,and coordination to a Lewis acid.Among them,the phosphole oxide derivatives and phosphole sulfide derivatives are special ones due to their high chemical and thermal stability.As a special form of phospholes,benzo[b]phosphole-based materials have been widely applied in organic electronic materials(including organic light-emitting diodes and photovoltaics),fluorescent bioimaging probes,photochromic diarylethene molecules al et.Therefore,the development of new and efficient routes for the synthesis of benzo[b]phosphole has been paid more and more attention.But,compared with benzothiophenes,benzofurans or indoles,their synthetic methods are relatively less.Herein we report two novel methods to synthesize benzo[b]phospholes based on an intramolecular cyclizing take advantage of catalytic reaction.And,based on this structure,we designed and synthesized new ladder-type conjugated molecules containing phosphole and silole,and investigated their optoelectronic properties.In chapter one,it demonstrates the reported methods for the preparation of benzo[b]phosphole derivatives according to different manners of reactions,and their applications in the field of advanced organic materials: semiconductor,optoelectronic materials,bioimaging probes,photochromic molecules,et al.Then,demonstrates a few of ?-conjugated diaryl-fused phosphole molecules which are used in the field of organic electronic materials science and environment-sensitive fluorescent probes.In chapter two,it described a new catalytic reaction using Pd/Cu bimetallic catalyst system to synthesize benzo[b]phosphole via P-C bond activation of stable tertiary phosphines.This protocol provides an atom-and step-efficient access to benzophospholes.But,this method still has a drawback: the yield is relative low.It is notable that this is not only a new method for the preparation of benzo[b]phosphole derivatives but also an new investigation of catalytic activation of C-P bonds of tertiary phosphine.In chapter three,it described a new air-contributing reaction of 2-alkynylphenylphosphine oxides to afford a benzo[b]phosphole oxides though P-centered radical process.This protocol provides a simple,additive-free,metal-free and environmentally friendly access to benzo[b]phosphole with excellent functional group compatibility and good isolated yield.And,based on the reaction mechanism,it also an effective method to phosphorus-doping polycyclic aromatic hydrocarbon.In chapter four,based on the reported method for the preparation of benzo[b]phosphole derivatives,we designed an ingenious method and synthesized a series of phosphorus and silicon-bridged stilbenes.These compounds showed the high fluorescence quantum yields both in solution and in the crystalline state.The organic light-emitting diodes using these compounds as emitters demonstrate that this new type of phospholes is a promising material for deep blue electroluminescent materials.It also should be pointed out that some compounds exhibited significant blue mechanoluminescence when the crystalline samples were scratched or crushed by a glass rod.