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À propos de : Silver Complexes with Unsaturated Thiacrown Ethers: InclusionBehavior of Conformationally Restricted Macrocycles        

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  • Silver Complexes with Unsaturated Thiacrown Ethers: InclusionBehavior of Conformationally Restricted Macrocycles
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  • The reactions of 18- and 21-membered unsaturated thiacrown ethers, 18-UT-6 and 21-UT-7, withCF3COOAg in acetone afforded novel silver(I) complexes AgI(18-UT-6)(CF3COO) and AgI2(21-UT-7)(CF3COO)2, respectively. The crystal structure of AgI(18-UT-6)(CF3COO) shows that the silveratom occupies the cavity of the 18-UT-6 and the geometry around the silver atom has a distortedfive-coordinate square pyramidal arrangement. The crystal structure of AgI2(21-UT-7)(CF3COO)2shows that the two silver atoms and all sulfur atoms are nearly coplanar and the two trifluoroacetategroups are located at the opposite sides of the plane. The stoichiometry for the complexation of15-UT-5, 18-UT-6, and 21-UT-7 with CF3COOAg in solution was examined by 1H NMR measurement. The titration plots of 15-UT-5 and 21-UT-7 show a distinct inflection point at 1:1 and 2:1metal/macrocycle ratios, respectively, whereas the plot of 18-UT-6 gradually changes at the rangeof 1:1 to 2:1. From these results, 15-UT-5 and 21-UT-7 were found to show inclusion selectivity fornumber of silver ions, respectively, whereas 18-UT-6 showed low selectivity for the inclusion numberof metals. Comparison of the oxidation and reduction potentials of the silver(I) complexes withthose of free macrocycles and CF3COOAg revealed that unsaturated thiacrown ethers becomedifficult to be oxidized by complexation with CF3COOAg, and CF3COOAg becomes difficult to bereduced by complexation with unsaturated thiacrown ethers.
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