A New 3D Coordination Polymer Based on Pentanuclear Cd(II) Rod-Shaped Secondary Building Unit: Synthesis, Crystal Structure and Luminescent Property

Journal of Inorganic and Organometallic Polymers and Materials, Sep 2014

A new coordination polymer [Cd2.5(μ3-OH)(L)2(bipy)]n (1). (L = 1,2-naphthalene dicarboxylate, bipy = 4,4′-bipyridine), was obtained under hydrothermal condition. The structure of 1 has been determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis and IR spectrum. Single-crystal X-ray diffraction analyses reveal that complex 1 crystallizes in triclinic system, Pī space group. Complex 1 possesses a 3D pcu net based on a pentanuclear Cd(II) cluster. Each pentanuclear Cd(II) cluster links with neighboring ones and generates a rod-shaped secondary building unit, which is further extended by bipy ligands to forms a three-dimensional network. Furthermore, the luminescent properties of this complex and the free ligand have been investigated. Complex 1 can be excited directly and emit strong soild-state fluorescence at room temperature, which may make them excellent candidates for fluorescent materials.

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A New 3D Coordination Polymer Based on Pentanuclear Cd(II) Rod-Shaped Secondary Building Unit: Synthesis, Crystal Structure and Luminescent Property

Hua-Rui Wang 0 Jian-Ge Wang 0 0 H.-R. Wang (&) J.-G. Wang College of Chemistry and Chemical Engineering, Luoyang Normal University , Luoyang 471022, People A new coordination polymer [Cd2.5(l3OH)(L)2(bipy)]n (1). (L = 1,2-naphthalene dicarboxylate, bipy = 4,40-bipyridine), was obtained under hydrothermal condition. The structure of 1 has been determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis and IR spectrum. Singlecrystal X-ray diffraction analyses reveal that complex 1 crystallizes in triclinic system, P space group. Complex 1 possesses a 3D pcu net based on a pentanuclear Cd(II) cluster. Each pentanuclear Cd(II) cluster links with neighboring ones and generates a rod-shaped secondary building unit, which is further extended by bipy ligands to forms a three-dimensional network. Furthermore, the luminescent properties of this complex and the free ligand have been investigated. Complex 1 can be excited directly and emit strong soild-state fluorescence at room temperature, which may make them excellent candidates for fluorescent materials. During the past two decades, metal-organic frameworks (MOFs), as an important class of crystalline solid materials, have received tremendous attention because of their potential in various applications, such as gas adsorption - and separation, catalysis, drug delivery, electrochemistry, molecular recognition, sensing, and detection [113]. The major task of the synthesis for such MOFs is to choose appropriate metal-connecting nodes and organic bridging ligands to control the formation of these complexes with required structures and properties. Among this topic realm, as an attractive subarea, homometallic cluster chemistry has been a small but growing family in recent years. In this case, homometallic cluster as secondary building units (SBUs) have been proved as an effective and powerful synthetic strategy in constructing new MOFs [14]. Depending on their architecture, MOFs based on polynuclear metallic units offer potential for unique properties, such as luminescence, magnetism and catalysis [15]. When the coordination number and geometry of metal centers are relatively fixed, organic ligands acting as bridging linkers to connect metal centers play the essential role [16]. From the point of view of organic ligand design, it is desirable to synthesize bulky ligands that have the coordinating atoms pointing on one side of the molecule, this favoring isolation of diverse discrete (dinuclear, tetranuclear, pentanuclear, or hexanuclear) and infinite (1D, 2D, or 3D) structures [17]. Following this strategy, the aromatic chelate ligand phthalic acid has been used as a good ligand for the construction of coordination polymers with polynuclear clusters due to the ability to bind more metals and isolate discrete metal cluster. For example, one decanuclear manganese [18] and three uranyl [19] compounds have been reported by G. Christou, in the presence of phthalate. To investigate the influence of bulky aromatic skeletons of such ligands on structures and properties of their coordination complexes, the naphthalene-based dicarboxyl ligand 1,2-naphthalene dicarboxylic acid (H2L), an expansion of phthalic acid, was chosen as the organic ligand in our recently work. To date, coordination Table 1 Crystallographic data and structure refinement parameters for complex 1 polymers constructed from the L ligand have rarely been synthesized. Also, the introduction of naphthalene based ligands into coordination polymers might lead to interesting luminescence properties of the final product. In this paper, we report the syntheses and characterizations of one coordination polymers [Cd2.5(l3-OH)(L)2(bipy)]n (1) based on 1,2-naphthalene dicarboxylic acid and 4,40-bipyridine. To our interest, this complex consists of pentanuclear Cd(II) rod-shaped SBUs and exhibits interesting luminescent properties. 2 Experimental Section 2.1 General Procedures All chemicals and reagents were used as received from commercial sources without further purification. All reactions were carried out under hydrothermal conditions. Elemental analyses (C, H, N) were determined with a Elementar Vario EL III elemental analyzer; IR spectra were recorded as KBr pellets on a Bruker EQUINOX55 spectrophotometer in the 4000400 cm-1 region. Fluorescence spectra were performed on a Hitachi F-4500 fluorescence spectrophotometer at room temperature. The X-ray powder diffraction pattern was recorded with a Pigaku D/Max 3III diffractometer. 2.2 Synthesis of Complex [Cd2.5(l3-OH)(L)2(bipy)]n (1) A mixture of H2L (10.8 mg, 0.05 mmol), Cd(OAc)2 2H2O (26.6 mg, 0.1 mmol), bipy (15.6 mg, 0.1 mmol) and KOH (5.6 mg, 0.1 mmol) were added to water (12 mL) in a 25 mL Teflon-lined stainless steel vessel. The mixture was heated at 180 C for 4 days. After the reactive mixture was slowly cooled to room temperature, colorless block crystals of 1 were obtained (yield: 50 %, based on Cd). Anal. C (...truncated)


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Hua-Rui Wang, Jian-Ge Wang. A New 3D Coordination Polymer Based on Pentanuclear Cd(II) Rod-Shaped Secondary Building Unit: Synthesis, Crystal Structure and Luminescent Property, Journal of Inorganic and Organometallic Polymers and Materials, 2014, pp. 971-976, Volume 24, Issue 6, DOI: 10.1007/s10904-014-0075-3