Synthesis, Structures And Properties And Theoretical Calculations Of Novel Metal-organic Nanotubes Based On Cyclodextrins

Metal-organic nanotubes (MONTs) or nanotubular architectures, as a special type of porous materials, have been attracting considerable attention from chemists and material scientists, due to their potential applications in the areas of gas adsorption, fluorescence and molecular sieves. Nanotubes play an important role in many research areas such as chemistry, materials, especially in terms of ion transport, molecular probes, simulation of molecular orbital and ion orbit show a huge advantage. For assembly of MONTs, it seems especially important to carefully choose organic ligands and metal ions, search crystallization conditions, including even the inclusion of guest molecules, and adopt appropriate synthesis strategies. Thanks to the development of supramolecular chemistry and crystal engineering, the application of multifunctional organic ligands to connect metal ions has led to numerous finite or infinite MONTs or nanotubular architectures. In particular, discrete MONTs remain less common to date. Recently, we and other groups successfully assembled1D non-interpenetrating MONTs based on mixed organic ligands under conventional or hydro/solvothermal conditions. Herein, we report two chiral discrete MONTs based on cyclodextrin (CD) synthesized through the biphasic scenario. The content of the thesis is listed as follows:(1) Two chiral lead metal-organic nanotubes (CD-MONT-2and CD-MONT-3) based on b-cyclodextrin ((3-CD) and g-cyclodextrin (y-CD) were synthesized through a biphasic solvothermal reaction. The lead ions were connected by two β-CD or y-CD molecules through their glycosidic oxygen atoms to generate a discrete metal-organic nanotube containing a {Pb14} or {Pb16} metallamacrocycle, respectively. Guest solvents of cyclohexanol molecules were trapped in the cavity of the β-CD-based nanotube, whereas there were no solvents in the cavity of the y-CD-based nanotube. These differences directly led to the formation of different3D packing structures. Their properties including temperature-dependent photoluminescence, adsorption of12molecules and thermal-decomposition behaviors were studied.(2) In order to realize the difficulty in cooperating CDs with lead ion, we performed first principle calculations on the complex of α-CD that cooperated with Pb(II) using the hybrid density functional theory method, in which the Beck three-parameter non-local exchange functional with the correction functional of Lee-Yang-Parr (B3LYP) was used. The initial geometry of a-CD was obtained from β-CD by cutting one pair of glucopyranose rings. CD-MONT-1-3based on α, β, γ cyclodextrins were fully optimized. The calculation results suggest that CD-MONT-1has the largest dihedral angle of Pb-O-Pb-0in this family, giving the Pb ring in CD-MONT-1the largest torsion. Hence, the condition for construction of a-CD-based MONT is harsh.