Electrochromic Phosphorescence Response Materials: Design, Synthesis And Optoelectronic Applications

Charged Ir(Ⅲ) complexes, mainly with oligopyridines as ancillary ligand, are receiving numerous interests due to their great potential in numerous fields, such as organic optical devices, chemosensors, and biological probes. That all are attributed to their promising photophysical properties, such as high phosphorescence efficiencies close to unity endowed by the strong spin–orbit coupling effect of the Ir(Ⅲ) atom, good photo- and thermal stabilities, as well as easy tunability of the emission color ionic character and good solubility in polar organic solvents or even in aqueous media. Charged Ir(Ⅲ) complexes also are the attractive candidates for stimuli-responsive luminescent materials due to their various charge-transfer excited states sensitive to external stimuli. In this thesis, we aims to develop stimulus-responsive charged phosphorescent materials and exploit their applications in optoelectronic devices. The primary contents are as follows:1. Ligand-controlled electrochromic phosphorescence response materials based on charged Ir(Ⅲ) complexesIn our recently work, a series of ionic Ir(Ⅲ) complexes with a N-H moiety in the N^N ligand, exhibit electrochromic phosphorescence attribute to the polarization of the N-H bond under the internal electric field. Based on this work, we designed and synthesized a series of charged Ir(Ⅲ) complexes with different C^N ligands. 2-Pyridyl-benzimidazole(pbimH) containing an N-H moiety has been selected as the ancillary ligand, which can interact with F- by forming hydrogen bonding and then further undergoing deprotonation, and it is also sensitive towards electric field. Interestingly, these phosphorescent complexes show different spectral responses to fluoride ions and electric field depending on their cyclometalating ligands, including quenched emission, blue shift and red shift response by F- and negative electrical stimulus. Multicolor ECL is realized by modifying the ligand or using a voltage-insensitive luminophore as background. Based on tpq IrNH, the self-encryption and data decryption via photoluminescence lifetime imaging microscopy(PLIM) was realized. Additionally, a multilevel information anti-counterfeiting has been realized utilizing the electric-field-induced changes in luminescence colors and lifetimes.2. The synthesis of multicationic Ir(Ⅲ) complex and the electrochromic phosphorescence responsesGiven the key role of the migration of small anionic counterions in electrochromic luminescence, we propose an effective strategy to improve the electrochromic luminescence performance by increasing the charge density of materials. Herein, two positively-charged imidazolium moieties have been respectively introduced into the C^N ligands of a cationic Ir(Ⅲ) complex CzpyIrNH. Thus, the obtained new complex im-CzpyIrNH carries three PF6- as counterions. At the same complex concentration, the anion concentration for multicationic im-CzpyIr NH is three times of that for a monocationic CzpyIrNH. Multicationic complex im-CzpyIr NH exhibited the higher sensitivity to the electric field and displayed more obvious luminescence color change under the same voltage. These results suggested that the introducing of more PF6- in one molecule would accelerate the formation of internal electric field, increase the sensitivity of the complex to the electric field, reduce the driving voltage and shorten the response time.3. Design, synthesis and electrochromic phosphorescence of charged Ir(Ⅲ) complexs with two hydroxyl functional groupsIn order to better understand the mechanism of electrochromic phosphorescence, three Ir(Ⅲ) complex with different cyclometalated ligands and with two hydroxyl functional groups N^N ligand has been synthesized. The phosphorescence properties of complex ppyIrOH and mppyIrOH exhibit obvious responsive to electrical stimulus, as well as to acid/alkali. That is because of the negative electric or the alkali can stabilize the alkali structures of the complexes, and the positive electric and the acid can stabilize the acid structures of the complexes.