Light Responsive Styrylpyridine Compounds And Iridium Complexes:Design,Synthesis And Properties

As an external stimulus,irradiation is an appealing candidate for its inherent advantages of efficiency and non-pollution.In addition,good maneuverability and readily available accuracy in regulation have also been the icing on the cake.Therefore,materials sensitive to irradiation have attracted a lot of research attention,whose structure undergoes specific changes to cause significant changes in properties have attracted widespread attention.Under irradiation of certain wavelength,the styrene compounds containing vinyl units can undergo a special structure-related photochemical process and finally cyclization appears.This reaction process has been proved to be extremely response sensitive.However,since the existence of spin-forbidden state,the intersystem crossing between the singlet state and the triplet state in organic systems have been very inefficient.The photochromic reactions in organic systems mainly related to the lowest-lying singlet excited state.Transition-metal complexes have been proved to possess lots of excellent photophysical properties,such as high efficiency of luminescence quantum,high tunability of emission wavelength and high sensitivity of phosphorescence emission.Besides these advantages,the iridium(III)complexes have abundant electronic transition states,which make themselves promising modifiable luminophore.Through the structural modification of the ligands,it is easy to control the excited state energy level,hence tune the phosphorescence properties of iridium(III)complexes.Introducing the photo-responsive units into the iridium(III)complex may achieve the sensitive phosphorescence response to external irradiation.According to this,styrylpyridine compounds have been designed and synthesized to study the response behavior to irradiation.Molecules of iridium(III)complex modified by styrylpyridine units have also been designed to achieve irradiation stimulated phosphorescence-responsive materials.This dissertation is comprised of the following two parts:1.Synthesis,characterization and response behavior of styrylpyridine compoundsTwo photoresponsive styrylpyridine compounds were synthesized.The photophysical and chemical properties of these compounds have been investigated.The steric hindrance produced by the pyridine ring methylation effectively enhances the regioselectivity in the cyclization process of styrene compounds and bring about the controllable cyclization response to irradiation stimulation.Oxidants have been used to manipulate the photocyclization process with the irradiation of ultraviolet.Under Ar atmosphere,the compounds underwent a cyclization reaction under UV irradiation.While in the presence of oxygen or the iodine as oxidants,the compound underwent a cyclization dehydrogenation reaction.These two processes were verified by nuclear magnetic resonance spectroscopy,UV-vis absorption spectroscopy and fluorescence emission spectroscopy.2.Synthesis,characterization and response behavior of iridium(III)complexes containing styrylpyridine unitsBased on the work of first section,three phosphorescent iridium(III)complexes containing the styrylpyridine unit were synthesized,and the phosphorescent response under visible light stimulation was realized.Upon visible light irradiating in the absence of oxygen,the styrene units in the ligand photocyclizated,giving a more rigid structure,and finally inhibited the phosphorescence quenching caused by vinyl isomerization.The phosphorescence intensity of iridium(III)complex has been enhanced by 4-20 times.However,since the sensitization of the complexes to strong oxidation singlet oxygen produced by oxygen,a series of accessory reaction emerged and pure cyclization products could not be obtained,hence the cyclization dehydrogenation process in the presence of oxygen was not observed.