Design,Synthesis And Electroluminochromism Properties Of Iridium(Ⅲ)Complexes Containing Viologen Units

Electroluminochromic materials are an emerging class of organic optoelectronic functional materials,with great potential in the fields of information display,information security,and data transmission.However,these materials have not been commercialized yet due to their relatively slow development and defects in material types and design strategies.Most of the electroluminochromic materials are small organic fluorescent dyes and polymers,of which the electro-responsive unit often quench the luminescence of materials by electron transfer.Compared with the fluorescence emission of pure organic materials,phosphorescent iridium complexes can achieve abundant emission colors and can also adjust the orbital energy levels and electronic transition mode through ligand modification with the virtue of high luminous efficiency,easily tunable emission wavelength,and rich excited state properties.Thus iridium complexes may provide electroluminochromic material an expand in the demention of luminescence intensity and wavelength response.Based on this,we introduced the viologen electro-responsive unit into the phosphorescent iridium complex to construct a new type of electroluminochromism material,which has potential in the fields of information display and anti-counterfeiting.The research includes the following two parts:1.Design,synthesis and properties of phosphorescent switching iridium complexesThe redox state of the phosphorescent iridium complexes based on viologen units changes under electric field,which leads to the change of the photoinduced electron transfer effect.These changes realize the reversible switch of the phosphorescent intensity.To expand the wavelength of electrostimulated photoluminescence,2-phenylpyridine and 2-(2,4-difluorophenyl)pyridine were selected as cyclometallic ligands to synthesize phosphorescent iridium complexes Ir1 and Ir2 with electroluminochromism behavior.After electrical stimulus,the emission wavelengths of iridium complexes Ir1 and Ir2 are restored at 524 nm and 610 nm,respectively,realizing the phosphorescence multi-color intensity response.The redox potential and the reversibility of electroluminochromism behavior were studied by electrochemical tests,and the experimental results were verified by theoretical calculations.Finally,the electroluminochromism behavior of iridium complexes has been applied to in optical information display.2.Design,synthesis and properties of phosphorescent wavelength iridium complexBased on the previous chapter,we found that the attachment site of the electro-responsive unit to the phosphorescent iridium complex has a great influence on its electrical stimulus-responsive behavior.Different attachment sites can affect the electron transfer between the electro-responsive unit and the metal center,as well as the conjugation degree of the organic ligand,consequently changing the electron transition mode of the phosphorescence emitting excited state.In order to realize the wavelength-responsive electroluminochromism behavior of iridium complex,we changed the attachment sites of the electro-responsive unit and transferred it from the N^N ligand to the C^N ligand to cut off photoinduced electron transfer.Thus the phosphorescent iridium complex are luminescence on and the luminescence wavelength will change before and after electric stimulus.Through photophysical and electrochemical tests along with theoretical calculations to verify the molecular design scheme.We found that the emission wavelength of iridium complex Ir3blue-shifted from the initial 602 nm to 544 nm under electric stimulus.This design strategy not only expands the material system of electroluminochromism materials,but also realizes the wavelength change of single-molecule materials before and after electric stimulus,which enriches the electroluminochromism behavior types.