| Research Abstract |
1. Structure and photoluminescence of square-antiprisrnatic ewopium(III) octahydrate ion+ in [Eu(H_2O)_2l_2[V_<10>O_<28>]・8H_2O were studied. The data provided information about a behavior of Eu^<3+> in aqueous solutions.
2. Photoluminescence and Tb^<3+>→Eu^<3+> energy transfer in [Tb_<1.4>Eu_<1.6>(H_2O)_3(SbW_9O_<33>)(W_5O_<18>)_3]^<18-> and [Tb_<4.3>Eu_<1.7>O_2(H_2O)_6Al_2(Nb_6O_<19>)_5]^<26-> with various Tb-Eu distances (3.8-6.0 A) were investigated. The results showed that the energy transfer occurs with dipole-dipole interaction of the Forster-Dexter type.
3 Five new rare earth (RE) polyoxotunstates, [(RE)_2(H_2O)_2(SbW_9O_<33>)(W_5O_<18>)_2]^<15->, [(RE)_3(H_2O)_4(SbW_9O_<33>)_2(W_5O_<18>)_2]^<21-> , [(RE)_2O(H_2O)(AsW_9O_<33>)_2]^<14->, [{(RE)(H_2O)_2(AsW_9O_<33>)}_4]^<24-> , [{(RE)(H_2O)_2(AsW_9O_<33>)}_6]^<36->, were prepared and structurally characterized. All the complexes ^consist of polyoxotungstate groups of the lacunary Keggin ([XW_9O_<33>]^<9->) and lacunary Lindqvist ([W_5O_<18>]^<6-> ) type, and RE^<3+> cations which act as linkers of the polyoxotungstate groups.
4. Population of RE^<3+> cations in [(RE)_2(H_2O)_2(SbW_9O_<33>)(W_5O_<18>)_2]^<15-> was studied for Y/Eu- and Eu/Lumixed systems with a help of photoluminescence spectroscopy and X-ray crystallography. The results revealed that one of the two RE sites is preferentially occupied by small RE^<3+> cation.
5. Structures were determined for new rare earth molybdates, (RE)_2Mo_5O_<18>, (RE)_6Mo_<12>O_<45>, (RE)_4Mo_7O_<27>, (RE)_6Mo_<10>O_<39>, which were formed by pyrolysis of [(RE)_2Mo_8O_<27>]・ 18H_2O (RE= Eu, Gd, Tb) at 750-800℃ for 2 h. We found that Eu_xGd__<2-x>Mo_5O_<18> (x=1.2) is a phosphor exhibiting significantly intense red photoluminescence.
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