| Summary: | 碩士 === 國立臺灣師範大學 === 化學學系 === 82 ===
Metal-induced changes are observed due to conformational rearrangements following complex formation. NMR spectroscopy has been applied to investigate complex. formation between crown ethers and metal ions. Conformations of the free and the complexed crown ethers have been studied using 13C NMR spectroscopy. The-strong influence of complexing on the chemical shifts of the single 13C NMR lines permits determination of the ligand-metal interactions.
C-pivot side-armed crown ethers form 1:1 complexes with Na+, 2:1 sandwich complexes with K+, and 1:1 complexes with Ag+. Morever, the complexing behavior of 2-picolyl sym-dibenzo-16-crown-5 ether varies significantly as concentrations of Ag+ changed. Yet, the complexing behavior of the ester-and chloro-side-armed crown ethers is less pronounced. The oxygen atom on the top of the bridged carbon chain plays an important role in the complexing process.
Two single crystals of the metal-crown ether complexes have been obtained and analyzed. Colorless crystal of sodium(hydroxy-sym-dibenzo-16-crown-5 ether) bromide crystallized in the orthorhombic space group P212121 with a=8.660(2), b=13.121(3), c=17.246(9)A, V=1960(1)A3,z=4,R=0.040,Rw=0.033. The molecule has a seven-coordinated structure. Blue crystal of [CuL2(H2O)2](ClO4)2(L=2-picolyl sym-dibenzo-16-crown-5 ether) crystallized in the monoclinic space group C2/c with a=21.332(3), b=14.218(7), c=36.21(2)A, β=91.60(3)°, V=10978(8)A(3), Z=8, R=0.109, Rw=0.106.
The molecule has a distorted octahedral structure.
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