| In the last few decades,phosphorescent iridium（Ⅲ）complexes have aroused great interest in the fields of nonlinear optics,organic electroluminescent devices,biosensors,cell imaging,and photodynamic therapy due to their high emission efficiency,stability,and appropriate bandgap energy.The simple solution-processable device structure,air-stable cathode,and low driving voltage make solid-state light-emitting electrochemical cells（LECs）a more promising lighting and display technology.To improve the efficiency of LECs,cationic iridium（Ⅲ）complexes have become one of the hot research objects in the field of LECs.Compared to pure organic small molecules,phosphorescent iridium（Ⅲ）complexes have much better intersystem crossing ability and can interact with surrounding oxygen to produce reactive oxygen species.Therefore,they also play an important role as effective antibacterial agents in photodynamic therapy for bacteria and cancer.In addition,the adjustable excited-state characteristics allow them to exhibit more advantages in the development of photocatalysts and nonlinear optical materials.The deep study of the relationship between molecular structure,electronic structure as well as aggregation form of materials and their performance can guide rational molecular design and synthesis in the future.This thesis will focus on the design,synthesis,and performance investigation of designed iridium（Ⅲ）complexes,and the detailed works are as follows.Firstly,we designed,synthesized,and theoretically studied two iridium（Ⅲ）complexes which comprise Phbd（1-phenyl-2-（pyridin-2-yl）-1H-benzo[d]imidazole）and Crbd（9-（4-（2-（pyridin-2-yl）-1H-benzol-1-yl）phenyl）-9H-carbazole）as ancillary ligands.The purpose of this work is to get to know the consequences of the displacements on geometrical,electronic structures,and second-order nonlinear optical（NLO）properties,UV-vis absorption spectrum.Here we get the first hyperpolarizabilities that can be easily adjustable by the introduction of Phbd and Crbd as ancillary ligands.Complex with Phbd shows higher first hyperpolarizabilities values as compared to that of the complex using Crbd as an ancillary ligand.Significantly,the modification of the first hyperpolarizabilities can be qualitatively elaborated utilizing the charge transfer pattern.Usually,it is estimated that the computational studies of the iridium（Ⅲ）complexes will be very supportive for designing high-performance and adaptable NLO materials.In our second work,we successfully designed and synthesized four cationic iridium（Ⅲ）complexes with pyridylbenzimidazol moieties as auxiliary ligands,namely ppy-Ir1,ppy-DIr1,ppy-Ir2 and ppy-DIr2.The novel iridium（Ⅲ）complexes exhibit strong emissions in the solution state,with emissions centered at ca.576,585,587,and 602 nm.Mononuclear complexes ppy-Ir1,ppy-Ir2 and dinuclear complexes ppy-DIr1 and ppy-DIr2 all exhibited high emission efficiency in the thin film state.In addition,the electrochemical data further demonstrated the excellent reversible redox properties of these complexes,which was favorable for the electroluminescent device.As a result,ppy-Ir2 endowed its orange device with peak efficiencies of 7.51 cd A-1,5.35 lm W-1,and 4.64%.In our third work,we investigated the successfully designed and synthesized three mononuclear and/or dinuclear cationic iridium（Ⅲ）complexes comprised of 1-（2,4-difluorophenyl）-1H-pyrazole main ligand and pyridine-triazole/pyridine-benzimidazole ancillary ligands,respectively.The photophysical properties and the photo-induced reactive oxygen species（ROS）generation abilities were also studied in detail.The results suggested that all complexes exhibit efficient emissions and excellent ROS production activities,which was in favor of imaging-guided photodynamic therapy（PDT）.In particular,the mononuclear complex M1 with pyridine-benzimidazole ancillary ligand has the best ROS generation ability and specific mitochondrial targeting.This work will show us more valuable information on the design of multifunctional iridium（Ⅲ）complexes for imaging-guided PDT in the future.In the fourth work,four novel iridium（Ⅲ）complexes with bulky cyclometalated ligands containing the spirofluorene units were designed,synthesized,and characterized.Their photophysical and electrochemical properties of them were investigated carefully.More interestingly,their emissions in the solution states were very weak,but they exhibited strong light in the crystalline state as well as nanoparticles.These data unambiguously demonstrated their aggregation-induced emission property.In addition,the cell imaging experiment as well as the reactive oxygen species（ROS）generation abilities of them were studied.The resulting nanoparticles based on these complexes can not only target the lipid droplets of living cancer cells but also hold the ability to produce ROS with a dominant Type I mechanism.The obtained data in this work will provide a molecule design strategy for iridium（Ⅲ）-based Type I photosensitizers in the future. |
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