Stimulus-Responsive Phosphorescent Iridium Complexes:Design,Synthesis And Properties

Stimulus-responsive materials can change physical and chemical properties under specific stimuli.Due to their remarkable properties,they are widely used in information encryption and information display.Among all stimulus-responsive materials,the materials that exhibit response to light and electricity have received much attention because of their broad application prospects.At present,viologens and diarylenes are the most widely used stimulus-responsive materials.In response to electrical and light stimuli,respectively,they usually exhibit changes in colors.Compared to organic fluorescent dyes,phosphorescence iridium(III)complexes show long luminescence lifetime and large Stoke shift,owing to the large spin-orbital coupling constant.This thesis is devoted to constructing novel phosphorescent iridium(III)complexes as smart stimulus-responsive materials.It includes two parts.1.Phosphorescent iridium(Ⅲ)complexes containing pyridinium units as stimuli-responsive materialsViologens containing two pyridinium units is a class of widely used electro-responsive organic molecules,which not only have a strong ability to accept electrons,but also can exist in the form of stable free radicals after reduced.Here,four iridium(Ⅲ)complexes have been designed,synthesized,characterized,and their photophysical and electrochemical properties investigated.Methylation of the pyridine modified complexes caused a red shift of the emission maxima of the complexes and reduced their quantum efficiency.In the titration experiment using KI as the titrant,the methylated complexes showed phosphorescence quenching.When the pyridinium units were reduced by sodium borohydride,the complexes displayed blue-shifted emission.Further investigation of the excited-state properties of the complexes have been studied by using theoretical calculation.This work provides new ideas for the construction of new electro-responsive phosphorescent iridium(Ⅲ)complexes.2.Phosphorescent iridium(Ⅲ)complexes containing vinyl units as stimuli-responsive materialsVinyl biphenyls are ready to undergo photocyclization under UV light stimulation.An novel iridium(III)complex containing vinyl modified cyclemetallating ligands has been designed,synthesized,and characterized.UV light irradiation on the complex resulted in cyclization confirmed by proton NMR spectra,leading to absorption response and 10-fold phosphorescence enhancement with lifetime elongation by 20 ns.Theoretical calculation has also been performed to understand the excited-state properties of the complexes.