Based on the investigation of the luminescence of a series of rare earth organic chelates, some relationships between luminescence and the structure of the chelates were proposed: the intensity of sensitized luminescence of central lanthanide ions(Ln3+) in a rare earth organic chelate depends on (1)the suitability of the energy gap between the excited triplet energy level of the ligands and the lowest excited energy level of Ln3+ ions; (2)the rigidity and planarity of the structure of the chelate molecule; (3)the existence of a suitable secondary ligand which may increase rigidity and the stability of the chelate molecule; and (4) the existence of a suitable π-conjugated system in the chelate molecule. According to the above relationships, 25 novel organic ligands were designed and synthesized, and their lanthanide chelates were prepared. Investigation of the photoluminescence for the new chelates shows that some of the chelates are strongly luminescent, and are applied to fluoroimmunoassay for determination of human immunoglobulin(IgG), to preparation of fluorescent plastics, and to determination of growth hormone for plants. Two novel spectroscopy-probe techniques for structure of coordination compounds and biological molecules were proposed and developed based on vibronic spectroscopy of Tb3+ complexes and fluorescence of Ce3+.

The use of cooperative vibronic spectroscopy to measure coordination numbers of the ligands surrounding rare earth ions in solutions was proposed and demonstrated. It is shown that the time-resolved cooperative vibronic spectroscopy is a very useful technique for the determination of the ligand type and ligand number for different coordination groups. Coordination configuration of arginine with Tb3+ in solutions with different pH values was studied. It demonstrates that the carboxy1 of arginine can replace H2O to coordinate with Tb3+ and the coordination number of carboxyl increases with the increase of pH value of the solutions.

Fluorescence of Ce3+(aq) is very strong and thoroughly quenched when Ce3+ forms complexes with ligands containing carboxylate or phosphate groups. This property is employed to develop a new simple method to determine formation constants of Ce3+ complex system. Fluorescence intensity is used to determine concentration of Ce3+ (aq) in complex solution, as it is proportional to the concentration of Ce3+ (aq). In this paper, two examples, Ce3+-malonic acid. and Ce3+-AMP(adenosine 5'-monophosphate), of fluorescence titration were made and association constants and association numbers of the two systems were deduced for the titration with Scatchard plot. The results are similar to those obtained by others. It is suggested that this Ce3+ method is a promising fluorescence probe, as it is not only simple but also superior to other lanthanide fluorescence probe in being able to study a large amount of organic ligands and biomolecules.

The structure of phenylalanine transfer ribonucleic acid (tRNA(Phe)) in solution was explored by H-1 NMR spectroscopy to evaluate the effect of lanthanide ion on the structural and conformational change. It was found that La3+ ions possess specific effects on the imino proton region of the H-1 NMR spectra for yeast tRNA(Phe). The dependence of the imino proton spectra of yeast tRNA(Phe) as a function of La3+ concentration was examined, and the results suggest that the tertiary base pair G(15). C-48, which is located in the terminal in the augmented dihydrouridine helix (D-helix), was markedly affected by La3+ (shifted to downfield by as much as 0.35). Base pair U-8. A(14) in yeast tRNA(Phe), which are stacked on G(15). C-48, was also affected by added La3+ when 1 similar to 2 Mg2+ were also present. Another imino proton that may be affected by La3+ in yeast tRNA(Phe) is that of the tertiary base pair G(19). C-56. The assignment of this resonance in yeast tRNA(Phe) is tentative since it is located in the region of highly overlapping resonances beween 12.6 and 12.2. This base pair helps to anchor the D-loop to the T Psi C loop. The binding of La3+ caused conformational change of tRNA, which is responsible for shifts to upfield or downfield in H-1 NMR spectra.

Five polyaminopolycarboxylic acids (EDTA and DTPA derivatives), DTPA . pAS, DTPA . 2pAS, DTPA . pAB, EDTA . pAS and EDTA pAB, where pAS and pAB represent p-aminosalicylate and p-aminobenzoate groups, respectively, were synthesized, and the stability constants of Tb3+ complexes with these ligands were determined, for the first time, by means of pH potentiometric titration. The complexation rates of Tb(III) with these ligands were found to be very slow, so batch technique was employed in the titration. The stepwise protonation constants of the lig ands and the stability constants of their Tb3+ complexes were calculated with the program BEST. It was shown that introducing p-aminosalicylate or p-aminobenzoate groups into EDTA or DTPA. leads to the decrease in acidity. The species distributions in the complex solutions at various pH accorded with the results of fluorescence measurements. A replacement of EDTA with DTPA . 2pAS in EDTA-Tb complex solution led to the enhancement in Tb3+ sensitized luminescence. The effects of the ligands' structure on the stability and fluorescence of the complexes were discussed.

Fluorescence of Ce(III) aqua ion at pH 6.0 is found to be in good linear relationship with its concentration, and the intensity is strong enough to be employed to determine its concentration. TRNAPhe evidently quench this fluorescence. Fluorescence titration experiments were performed to Ce(III)-tRNAPhe system, the binding number and association constant was estimated with a Scatchard plot. Two classes of binding sites with association constant of 5.2 × 107 and 4.4 × 106 M, respectively, were found. Addition of spermine slightly decrease binding number and association constant of Ce(III) ion.

Tb3+ and EU(3+) complexes of N, N', N "-1, 3, 5-triazine-2, 4, 6-triyltris-[N-(carboxymethyl)]-glycine were synthesized and characterized by elemental analysis, TG-DTA, UV, IR, fluorescence and phosphorescence spectroscopy. It was shown that the ligand can sensitize the fluorescence of Tb3+ but not sensitize the luminescence of EU(3+). Th, mechanism of luminescence was discussed based upon the phosphorescence of the ligand.

Time-resolved two-center cooperative vibronic transition involving a rare earth ion and a vibrational group of a ligand is shown to be a useful background-free infrared technique for the determination of the ligand structures surrounding trivalent rare earth ions. Several frequently encountered groups in biomolecular systems are studied using trivalent terbium ions as probes in solids and in liquids. The microstructures of the rare earth compounds determined with the two-center cooperative vibronic transition are found to be in agreement with those determined using other techniques.