Synthesis,Characterization And Applications Of Phosphorus And Nitrogen Heterocyclic Functional Molecules

Heteroatoms doped organic functional materials exhibit diversity and functionality,which can not be realized by the carbon-only materials.The doping of different heteroatoms can effectively regulate the molecular energy levels and affect the intermolecular interactions and improve the stability of molecules,owing to different atomic sizes,electronic properties and coordination modes.The study of phospholes and their derivatives has been a crucial part of phosphorus chemistry,which facilitates the development of organic synthesis,coordination catalysis,functional materials,biologic pharmacy and other fields.The trigonal pyramidal configuration of the tricoordinate phosphorus prevents the valid conjugation from the lone pair and the ?-electrons of dienes,which decreases the molecular aromaticity.Nonetheless,the ?-? hyperconjugation of the exocyclic P-R ? bond and the endocyclic ? system enriched the reactivity of the phosphole;the interaction of antibonding orbitals lower the energy levels of LUMO,which do favors to electron injection and transport.The simply chemical modifications of P atom paves the way for effective regulations of the molecular electronic property,which can not be realized in other heterocycles.Therefore,the incorporation of phosphorus atoms into the ? conjugation system provides an opportunity for the design of new organic functional molecules and the optimization of their photoelectrical properties.Nitrogen containing heterocycles,especially pyrrole derivatives,usually have intense fluorescence emission,excellent carrier mobility and good self-assembly performance,which can be applied in hole transport materials,photochromic materials,fluorescent probes and supramolecular self-assembly.Extensive researches of the chemistry of phospholes or pyrroles have been explored by numerous scientists due to their peculiar and controllable properties.However,P,N-codoped organic functional molecules have not been well developed.Based on the above viewpoints,several heterocyclic functional molecules containing both phosphorus and nitrogen have been designed and synthesized.Initial explorations of these P,N-functional molecules were investigated through the characterization of their structure and photoelectrical properties,and some applications of these compounds in novel organic materials have been carried out.In the first chapter,the applications of phosphole-based materials were reviewed systematically in different functions,i.e.,Organic Light-Emitting Diodes(OLEDs),Organic Photovoltaics(OPVs),fluorescent probes and photochromics.The applications of P,N-codoped materials were also presented.In the second chapter,the synthesis,characterization and optical applications of 1,3-azaphospholes with a pyrrolo[1,2-a]quinoline skeleton were studied.The optical and electrochemical properties of 1,3-azaphospholes with different conjugation lengths and modifications on P atom were studied.The 1,3-azaphospholes could be employed as emitting dopant in TADF-sensitized OLEDs owing to high photoluminescence efficiency,stable emission and high thermostability.Moreover,it could also be used as dye for bioimaging with good membrane permeability and ultralow cytotoxicity,which indicated the potentials of these molecules in biological imaging,fluorescence probes and other fields.In the third chapter,an intramolecular noncatalyzed SEAr reaction of chlorophosphine to give the five-membered phosphole was investigated.The reaction was simple,efficient,economic and offered a new stratagy to access P-N ladder-type heteroacenes.A series of tetra-,penta-,hexa-and hepta-cycle fused molecules with highly planarity were synthesized and their photoelectrical properties were characterized.In addition,terminal methyl sulphides were introduced into the extended conjugation molecules as anchoring groups,which can form single molecular junctions through scanning tunneling microscopy break junctions(STM-BJ)methods with high conductance.Both experiment and theoretical calculations demonstrated that configurations and electron nature on phosphrous atom have a profound impact in single-molecule conductivity of these P-N ladder-type heteroacenes.The results could offer new approaches to tune the charge transport in molecular materials and devices.In the last chapter,carbazole-?-phosphonium compounds were synthesized handily and efficiently.The optical,electrochemical and thermodynamic properties were characterized and analysed.DFT calculations were also performed in order to get inside into their frontier molecular orbitals.The ionic characteristics of the phosphoniums provide a new strategy for the design of dipolar molecules.This kind of dipolar molecules have potentials to be used in TADF materials and charge transport materials owing to the strong donor-strong acceptor structure,favourable luminescence efficiency and good thermostability.