The Optical Functions Of Rare Earth Complexes Of Molecular Design, Synthesis And Structure-activity Relationship Study

As luminescence materials, lanthanide complexes have several advantages, such as extremely sharp emission bands, high quantum efficiency and modification of the ligands without affecting the emission characteristics of the central ion. So the lanthanide complexes have important applicant value in organic electroluminescence devices and fluorescent probe. This thesis is focused on the design and synthesis of fluorescent lanthanide complexes and studying the relationship of structure-activity. The contents are as follows:1. For the good energy transfer property of the pyrazolone-based ligands (HLA and HLB), the corresponding terbium complexes show good electroluminescence properties. Six new pyrazolone-based ligands HL1～ HL6 were synthesized by introducing electron-poor or electron-rich aryl substituents at 4-position of the pyrazolone ring and their corresponding lanthanide complexes Ln(LX)₃(H₂O)₂ (X = 1～6) (Ln = Eu, Gd) were also studied. The experimental results indicate that: (1) It is available for tuning the singlet and triplet energy level of the pyrazolone-based ligands by introducing electron-poor or electron-rich aryl substituents at 4-position of the pyrazolone ring; (2) The modified pyrazolone-based ligands can sensitize Eu³⁺, therefore their europium complexes emit the characteristic emission of Eu³⁺, because the triplet energy levels of these ligands match the ⁵D₀ energy level of Eu³⁺; (3) The fluorescence quantum efficiency and lifetime were determined by the experiment of fluorescent annihilation. We noted that the structure modification of the organic ligands influenced the efficiency of energy transfer (φtransfer) from the ligand to the Eu³⁺ and the emission efficiency of lanthanide ion (φLn). In addition, a series of trinary europium complexes Eu(LX)₃(TPPO)₂ (X = 1～6) were synthesized by introducing the neutral ligand of triphenylphosphine oxide (TPPO). An organic electroluminescence device was fabricated by using Eu(L1)₃(TPPO)(H₂O) as luminescent material. The device emited pure red light with the highest luminance of 247 cd/m².2. Similarly, the dependence of diacetone-based derivants' structure (HAcAc, HAcB, HDBM, HCDBM and HNDBM) on the luminescent property of Eu³⁺ was studied. Theexperimental result indicated that the triplet energy levels of ligands gradually decreased with increasing of the conjugate system. The energy level of ligand HDBM perfectly match the ⁵D₀ energy level of Eu³⁺, so the fluorescent quantum efficiency of Eu(DBM)₃(H₂O)₂ is the highest among these europium complexes. At the same time, we noted that the singlet and triplet energy levels of ligand HCDBM and the fluorescent properties of Eu(CDBM)₃(H₂O)₂ were different under different temperature and in the different polar solvent. This was due to the influence of temperature and solvent polarity to the conjugate system between the p-carbazolyl and β-diketone.3. Base on the strong bonding ability of Eu³⁺ and F^-, we designed and synthesized two europium complexes [Eu(NO₃)₃(TPPO)₃, Eu(NO₃)₃(TMPO)₃] and applied them to chemsensors for fluoride anion. For example, the fluorescent intensity of Eu(III) character emission constantly decreased when F^- was added to the solution of Eu(NO₃)₃(TPPO)₃. The ³¹PNMR spectrum showed that the mechanism of the sensor was the bonding of Eu³⁺ and F^-. These europium complexes had the highest sensitization for fluoride anion among the familiar anions, such as Cl^-, Br^-,I^,C104^-, Ac^- and H₂PO₄^-. The experimental results indicated that these europium complexes will be able to be used as fluoride sensor. Moreover, the strong background fluorescent (BGF) was eliminated by using time-resolved luminescence technology. Even though the intensity of BGF was 1000 times than the intensity of detected ion, the europium complexes could be used as the chemsensor of the fluoride anion.4. A series of lanthanide complexes (Ln = Er, Nd, Yb) with infrared emission properties were designed and synthesized by using different anionic ligands [1 -phenyl-3-methyl-4-(4-tertbutylbenzoyl)-5-pyrazolone (tbup-PMP) and l-phenyl-3-methyl-4-(isobutyl)-5-pyrazolone (ip-PMP) and 2-naphtoyl trifluoroacetone (NTA)] and netural ligands (2,2-dipyridine, phenanthroline, triphenylphosphine oxide and water). Three crystal structures of these complexes were obtained and structure studied, and the properties of photoluminescence and fluorescent lifetime were studied in detail. We found that the existance of H₂O quenched the fluorescent emission of these complexes.5. We also studied the electroluminescent and electrochemical properties of five organoboron compounds with the B(Mes)2 as acceptor (Mes = 2,4,6-trimethylphenyl). The properties of these compounds were great different, and the compound B3 was screenedout as the best blue luminance material among them. The experiment results indicated that B3 had the ability of current carrier transfer and it was a good blue electroluminescent material. At the same time, B3 can also be used as a host material which efficiently transfer the energy to the indium complex. The device emited red light and had high electroluminescent performance. The HOMO and LUMO energy levels were determined from the corresponding oxidation and reduction potentials. We interpreted the different EL properties of these compounds according to matching of the energy levels.