Now showing 1 - 2 of 2
  • Publication
    Mechanism of Atmospheric CO2 Fixation in the Cavities of a Dinuclear Cryptate
    Using density functional theory (DFT) methods, we have investigated two possible mechanisms for atmospheric CO2 fixation in the cavity of the dinuclear zinc (II) octaazacryptate, and the subsequent reaction with methanol whereby this latter reaction transforms the (essentially) chemically inert CO2 into useful products. The first mechanism (I) was proposed by Chen et al. [Chem. Asian J. 2007, 2, 710], and involves the attachment of one CO2 molecule onto the hydroxyl-cryptate form, resulting in the formation of a bicarbonate-cryptate species and subsequent reaction with one methanol molecule. In addition, we suggest another mechanism that is initiated via the attachment of a methanol molecule onto one of the Zn-centres, yielding a methoxy-cryptate species. The product is used to activate a CO2 molecule and generate a methoxycarbonate-cryptate. The energy profiles of both mechanisms were determined and we conclude that, while both mechanisms are energetically feasible, free energy profiles suggest that the scheme proposed by Chen et al. is most likely.
    Scopus© Citations 22  1140
  • Publication
    A theoretical thermodynamic investigation of cascade reactions in dinuclear octa-azacryptates involving carbon dioxide
    This paper investigates the thermodynamics of gas-phase CO2 cascade uptake-reactions in the form of carbonate or methoxycarbonate anions in the host cavity of various dinuclear octa-azacryptates of m-CH2C6H4CH2 and 2,5-furano-spaced hosts, L1 and L2 cryptands, using density functional theory (DFT). The cascade process involves two stages, namely the formation of dinuclear cryptate complexes and the subsequent formation of either μ-carbonato cryptate complexes or μ-monomethylcarbonato cryptates. The geometric and electronic structures are also investigated to determine the parameters which affect the stability of the complexes. Natural bond orbital (NBO) analysis has been used to investigate the interactions between the trapped anion and its host. The ion selectivity has been studied in terms of the formation of dinuclear crypate complexes, while the basicity and nucleophilicity of cryptands towards Lewis acids have also been studied, and good agreement was found vis-à-vis available experimental data.
    Scopus© Citations 5  853