Formation of Cadmium(￥±) Nitrate Complexes with Macrocycles

摘要

The twelve macrocycle (L) complexes of cadmium(ケ) nitrate have been synthesized: CdL(NO3)2. All the complexes have been indentified by elemental analysis, electric conductivity measurements, IR and NMR spectroscopic techniques. The molar electric conductivities of the complexes in water and acetonitrile solvent were in the range of 236.8-296.1 cm2·mol-1· ohm-1 at 25∩. The characteristic peaks of macrocycles affected from Cd(ケ) were shifted to lower frequencies as compared with uncomplexed macrocycles. A complex with 1,4,8,11-tetrakis(methylacetato)-1,4,8,11-tetraaza cyclodecane (L4) exhibited two characteristic bands such as strong stretching (1646 cm-1), and weaker symmetric stretching band (1384 cm-1). NMR studies indicated that all nitrogen donor atoms of macrocycles have greater affinity to cadmium(ケ) metal ion than do the oxygen atoms. The 13C-resonance lines of methylene groups neighboring the donor atom such as N and S were shifted to a direction of high magnetic field and the order of chemical shifts were L1 < L2 < L3 < L6 < L4. Also the chemical shifts values were larger than those of methylene groups bridgeheaded in side-armed groups. This result seems due to not only the strong interaction of Cd(ケ) with nitrogen donors according to the HSAB theory, but weak interaction of Cd(ケ) and COO- ions or sulfur which is enhanced by the flexible methylene spacing group in side-armed groups. Thus, each additional gem-methyl pairs of L3, L4 and L6 macrocycles relative to L1, L2, and L5 leads to an large enhancement in Cd(ケ) affinity. 13C-NMR spectrum of the complex with L12 (1,5,9,13-tetracyclothiacyclohexadecane-3,11-diol) reveals the presence of two sets of three resonance lines, and intensities of the each resonance line have the ratio of 1 : 2 : 2. This molecular conformation is predicted as structure of tetragonal complex to be formed by coordinating two sulfur atoms and the other two sulfur atoms which is affected by OH-groups.