| Chiral synthesis and enantiomeric separation are not only one of the hottest and most difficult areas in organic chemistry and pharmaceutical chemistry, but also a new frontier of supramolecular chemistry. Chiral supermolecule involving supramolecular chemistry and chirality of molecules is extensively studied in many areas, such as asymmetric catalysis, enantiomeric separation, nonlinear optics, functional materials and molecule recognition. In recent years, the development of coordination chemistry and especially of supramolecular chemistry promotes the research on design and synthesis of chrial porous coordination polymers, and thus many novel strategies have been raised.In this paper, a novel chiral ligand S-2(4-(2,6-di(pyridin-2-yl)pyridin-4-yl)benzylamino)propanoic acid (H2ptpy) with a hugely conjugated framework was intentionally synthesized and used to construct 9 chiral complexes, namely, [Hg2(H2ptpy)2(I)4]·2H2O (1), [Cu(Hptpy)2]·2N(CN)2-4H2O (2), [Cd2(Hptpy)2(Ac)2]·3CH3OH·H2O (3), [Ni2(Hptpy)2(H2O)2](SCN)2 (4), [Ni2(Hptpy)2(N3)2]·7H2O (5), [Ni2(Hptpy)2(N3)(H2O)](N3)·19H2O (6), [Mn2(Hptpy)2]·2N(CN)2·2H2O (7), [Mn4(Hptpy)4(H2O)2]·2N(CN)2-2H2O (8) and [Cu8(Hptpy)4(TPA)6]-4H2O (9) [Ac=acetate; TPA=terephthalic acid anion].These complexes all have been determined by single crystal X-ray diffraction analysis. Their photoelectronic properties, stabilities and magnetic properties have been systematically investigated, and the correlations between structures and properties have been also discussed. Complex 1 contains two chiral mononuclear complexes cocrystallized together. Every Hg(II) adopts a distorted square-pyramidal coordination symmetry. The chiral expansion along a axis is achieved through hydrogen-bonding connections between the chiral mononuclear complexes, and two different chiral 1D chains are obtained. Complexes 2-6 are all chiral dinuclear metallocycles constructed by the two same M(II) [M(II)=Cd(II) and Ni(II)] cyclized by two chiral Hptpy anions in a head-tail bridge style. In complex 2, every Cu(II) adopts a distorted square-pyramidal coordination symmetry. But in complex 2-6, the six site of the distorted coordination octahedron of every M(Ⅱ) is occupied by O or N atom from solvents or counteranions. These similar dinuclear metallocycles in 2-6 are further aggregated into complicated chiral supramolecular architectures or template novel chiral water chains and a chiral 3D zeolite-like water-net due to the differences in counter anions and solvents. Complex 7-9 are all 1D chains:the chain in complex 7 was constucted by chiral metallocycles by the bridge coordination of 0 atoms of the carboxyl; besides the similar 1D chain in complex 7, complex 8 has another chiral chain by hydrogen-bonding connections between dinuclear metallocycles, and the two chiral chains are vertical each other. Complex 7 and 8 are obtained by hydrothermal and slow evaporation synthesis with the same reactants, respectively. The two complexes can be transformed each other by controlling the synthesis temperature. Very interestingly, the differences in structures of complex 7 and 8 result the interesting differences in their magnetic properties. In complex 9, the secondary ligand TPA participates in coordination and as a result breaks down the chiral dinuclear metallocycles to form a 1D double chain.Ligand H2ptpy and complexes 1-9 have been systematically studied by IR and solution-state UV-vis. The global stable constant of 3 [lgβ=17.60] is calculated by spectrophotometric titrations method, which certificates that the chiral dinuclear metallocycles is of high stability and belongs to thermodynamically stable species. The CD spectrum illustrates complex 8 and others constructed by the chrial ligand H2ptpy have obviously chiral properties. This paper has definite significance in futher research on the construction of novel chiral metal-organic supermolecules assembled by chiral ligands or the formation of fantastic guest supermolecules induced by chiral hosts. |
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