| This dissertation is consisted of the following four chapters.In the first chapter, the recent work on the anion recognition and small molecule activation by azacryptands and dinuclear azacryptates are briefly reviewed, and the future development of research about dinuclear azacryptates is also introduced.In the second chapter, the crystal structures of [Co2L1(μ-Cl)](ClO4)3, [Co2L1(μ-Br)](ClO4)3, [Co2L1(OH)(OH2)]I3 and [Co2L2(μ-Cl)](ClO4)3 (L1 = N[(CH2)2 NHCH2(C6H4-p)CH2NH(CH2)2]3N, L2 = N[(CH2)2NHCH2(C6H4-m)CH2NH(CH2)2]3N), the DFT calculations, as well as the binding constants of [Co2 L1 ]4+towards Cl- and Br-, and [Co2 L2 ]4+ towards Cl- have been reported. The rigid dinuclear cryptate [Co2L1]4+ shows the recognition of Cl- and Br-, but not of F- and I-, due to the size matching to its rigid cavity. It has also been found that the relative rigid tripodal skeleton of L1 than L2 result in the higher affinity of [Co2 L1 ]4+ towards Cl-. Magnetic susceptibility measurements of [Co2L1(μ-Cl)](ClO4)3 and [Co2L1(μ-Br)](ClO4)3 indicate that the two Co(II) ions in cryptates are antiferromagnetically coupled through the Cl-/Br- bridge.In the third chapter, it has been found that dinuclear metal cryptates [M2L2](ClO4)4 (M = Cu(II), Zn(II)) can easily take up atmospheric CO2 even under the weak acidic condition at room temperature, and convert it from bicarbonate into carbonate monoesters in alcohol solutions. The bicarbonate-bridged and a series of monoalkylcarbonate-bridged dinuclear cryptates have been characterized by IR, ESI-MS spectroscopy and single-crystal X-ray diffraction analyses. A reasonable mechanism for CO2 fixation and esterification is presented based on the results of crystal structures, solution studies and DFT calculations. The extremely low pKa value for [M2L2(OH)]3+ let [M2L2]4+ facilely take up atmospheric CO2 to formμ-O2COH- bridged compound under the weak acidic medium, followed a mechanism of bicarbonate formation. The coordination ofμ-O2COH- to two metal ions activates its carboxyl carbon atom so it is easier to be attacked by the primary alcohols via tetrahedral intermediates to generate monoalkylcarbonate-bridged compounds. Moreover, the different reactivity between [Cu2L1]4+ and [Cu2L2]4+ is also discussed.In the fourth chapter, the reactions of L2 with heavy metal salts CdCl2 and Pb(NO3)2 in the presence of NaClO4 gave two dinuclear cryptates, [Cd2L2(μ-Cl)](CdCl4) (ClO4)·CH3OH and [Pb2L2(μ-NO3)](ClO4)3·CH3OH·0.5CH3CN, respectively, and the crystal structures as well as DFT calculations have been reported. The results demonstrate that L2 can form stable dinuclear cryptates with toxic heavy metal ions.
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