纳米分子筛构建

Received April 14th, 2004. Abstract. A 2D grid-shaped bimetallic imidazolate polymer [CoIICuI2(Im)4]ϱ (1) was solvothermally synthesized and characterized with single crystal X-ray analysis: tetragonal space group ˚ , c ϭ 6.3063(13) A ˚, V ϭ ¯ 21/c (No.114), a ϭ b ϭ 10.9513(15) A P4 ˚ 3. This is the first cobalt(II) imidazolate polymer hy756.3(2) A bridized with other transition metals. Keywords: N-Heterocycles; Cobalt; Copper; Coordination polymers; Solvothermal synthesis
pentanol (EP) under solvothermal conditions at 140 °C. Obviously, the obtained cuprous compound was due to a redox reaction between the CuII ion and the organic components under solvothermal conditions. The x-ray single crystal analysis reveals one cobalt(II) and one copper(I) ion in the asymmetric unit of 1, in which the tetrahedrally coordinated cobalt(II) atom is on the inversion axis Ϫ4, whereas the linearly coordinated copper(I) ion is on the 21 screw axis; the atoms are bridged by a deprotonated imidazole molecule (Fig. 1a). The crystal structure of 1 consists of parrallel corrugated sheets in the ab-plane, made up of edge-sharing square [CoCu2(Im)4]ϱ units with CoII at each of the 4-connected corners (the four dihedral angles between adjacent imidazolato are 61.6(2)°, and two dihedral angles between opposite imidazolato ligands are 92.8(2)°) and CuI in the middle of each of the 2-connected linear edges (the dihedral angles between adjacent imidazolato ligands are 97.3(2)°). This generates a square grid with a Co···Co distance representing the edge parameter that is equal to the crystal unit-cell a and b. If the van der Waals radii are taken into consideration, this grid gives rise to an effective opening of 0.955 nm (Fig. 1b). However, because the sheets are stacked along the c-axis in the ABAB manner (Fig. 2), and the sheets A to B are translated with 1/2a and 1/2b in the ab-plane, the grid openings of the sheets are offset and the adjacent ˚ (0.35 A ˚ longer than layers maintain a Cu···Cu distance of 3.15 A ˚ two times 1.40 A, the van der Waals radius of copper) that represents only a very weak metal-metal interaction. Silica hybridized with alumina are defined as zeolites. Changing the ratio of silica to alumina in the reaction mixture to produce a desired aluminum content not only will cause a change in the aluminum concentration in the zeolitic structure, but may also result in a change in the final structure obtained [10]. Therefore, changing the ratio of cobalt(II) to copper(I) could have been regarded as a synthetic strategy for gaining zeolitic structures of metal imidazolates. However, the experiment has demonstrated that the ratio of cobalt(II) to copper(I) in the cobalt(II)-copper(I) bimetallic imidazolate polymer is fixed due to the highly defined coordination geometries of the metal atoms. Therefore, no matter how we have varied the CoII/CuI ratio in the reaction mixture, compound 1 was always obtained. Nevertheless, the existence of other structures of the compound with the same Co/Cu ratio cannot be excluded since the other synthetic variables, such as templates or solvents, may influence the structure obtained. Although 3D heterobimetallic imidazolate polymers are highly expected, the 2D
a b
Nanjing/China, State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing University Shenyang / China, Depawenku.baidu.comtment of Chemistry, Liaoning University
Imidazolate-bridged bimetallic complexes are model compounds for some metallic enzymes [1Ϫ4], of which the copper-zinc superoxide dismutase (Cu, Zn-SOD) is highly modeled and studied [1Ϫ3]. Imidazolate-bridged poly-metallic oligomer or polymers have previously been synthesized for magnetic studies of the imidazolatoinduced magnetic coupling [5, 6]. However, we found recently that the imidazolate-bridged CoII homopolymers can form 3D frameworks, which exhibit silica-like extended polymorphism [7], that are currently interesting motifs of metal-organic porous materials. In order to create zeolite-like or aluminophosphate-like structures of metal imidazolates, we have studied not only the solvothermal synthetic mechanism [8] of the metal imidazolate polymers, but also the possibilities for hybridizing the cobalt(II) imidazolate polymer with other transition metals of the MI or MIII type. Up to now, although we have tested the preparation of the cobalt(II) imidazolate polymers mixed with FeIII, RuIII, CrIII or AgI and CuI moieties, the desired heterobimetallic coordination motifs have been difficult to obtain since the coordination nature of CoII is different from those of the MIII metal ions. With regard to the AgI-involved cobalt(II) bimetallic polymer, the silver(I) imidazolate homopolymer can be synthesized even at room temperature [9]; however, under solvothermal conditions, a metal imidazolate complex containing AgI cannot be obtained due to the highly oxidative nature of AgI. Nevertheless, the CuI-involved cobalt(II) imidazolate polymer was obtained by solvothermal synthesis. Here, we report the synthesis and X-ray crystal structure of this bimetallic coordination polymer. The bimetallic imidazolate polymer, formulated as [CoIICu2I(im)4]ϱ (1), is stable in air and is prepared by reacting Cu(CH3COO)2·H2O, Co(CH3COO)2·4H2O, imidazole and triethanolamine in 2-ethyl-1-
[CoIICuI2(Im)4]ؕ: A Layered Bimetallic Imidazolate Polymer, the First Hybridized Cobalt(II) Imidazolate
Yun-Qi Tiana,b,*, Hai-Jun-Xua, Yi-Zhi Lia, and Xiao-Zeng Youa,*