Flux Growth of Tungsten Oxychloride Li23CuW10O40Cl5

LI Shufang, ZHAO Shuang, LI Manrong

Flux Growth of Tungsten Oxychloride Li23CuW10O40Cl5

LI Shufang, ZHAO Shuang, LI Manrong

(Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China)

Mixed anion compounds can generate the emergence of novel properties that differ from those with mono-type anion due to the difference of electronegativities, ionic radii, polarizabilities, and oxidation states between unlike anions. Abundant research has been conducted on metallic mixed-anion materials with potential application in electronics, detectors of moisture, gas sensors, electrodes for solar batteries,The flux method has been widely applied for mixed-anion crystal growth, which based on metathetical reaction with appropriate metal-salts ?ux under mild conditions. It is meaningful to synthesize the mixed anion compounds by the flux method. Singlecrystals of tungsten oxychloride Li23CuW10O40Cl5were preparedCuCl2flux-growth method by two steps, which using high quality and phase-pure polycrystalline Li4WO5as precursor. The crystal structure was determined by single-crystal X-ray diffraction analysis, which indicates that Li23CuW10O40Cl5crystallizes in P63/mcm space group (= 1.02846(3) nm,=1.98768(9) nm,=1.82076(11) nm3, and=2). There are crystallographically independent five Li, two W, one Cu, two Cl, and five O atoms in the unit cell, where W(1) atoms are coordinated with one Cl and five O atoms in a distorted octahedra geometry, while W(2) atoms are connected with four O atoms in a tetrahedral coordination. The Cu atoms are connected with six O atoms forming [CuO6] octahedra. Thus, the crystal structure of the titled compound consists of [CuO6] and [W(1)O5Cl] octahedra, and [W(2)O4] tetrahedra. The successful synthesis oftungsten oxychloride Li23CuW10O40Cl5through flux-growth method is meaningful for explore new mixed anion compounds in future.

tungsten oxychloride; CuCl2flux; crystal structure; X-ray diffraction

Mixed anion compounds, especially their unique structures and excellent physical properties, have been extensively studied and have great applications in mili-tary and civilization. They have attracted abundant atten-tion since the difference of electronegativities, ionic radii, polarizabilities, and oxidation states between unlike ani-ons can generate the emergence of novel properties that differ from those with mono-type anion[1-4]. The active research of metallic mixed-anion materials with potential application in electronics, detectors of moisture, gas sensors, electrodes for solar batteries,has been real-ized in several types of crystalline and thin ?lm materi-als[5]. It is meaningful to search a suitable method to synthesize aforementioned compounds. The main hotpot to research this kind of compounds lies in how to control the arrangement of anions to refine their electronic structures, such as the two-dimensional quantum anti-ferromagnetism in Sr2CuO2Cl2with trans-configuration of Cl ions in the CuO4Cl2octahedra[6].

Recently, it has been reported that incorporation of halides into oxides can strikingly change their electronic structures and modify the physical properties[7-8]. Several novel transition-metal oxychlorides have been reported to date, such as MnSb4O6Cl2[9], PbCu2(SeO3)2Cl2[10], Cu3Bi(SeO3)2O2Cl[11], FeTe2O5X (X=Cl, Br)[12], SrCu2(SeO3)2Cl2[13], SmSb2O4Cl[14], and MSb2O3(OH)Cl (M=Co, Fe, Mn)[15]. Above-mentioned materials show novel structures and special magnetic properties due to their diversity structural which was more helpful to gen-erate the magnetic ordering during low temperature. This was especially manifested in layered transition metal oxyhalide FeTe2O5X (X=Br, Cl), where the layers are built by [FeO6] octahedra, and then forming the [Fe4O16]20–units which were linked[Te4O10X2]6–anionic groups. The magnetic properties are reported within a cluster approach of antiferromagnetically coupled tetramers including spin frustration and a ferromagnetic inter- tetramer interaction[12].

The flux method widely applied for mixed-anion crystal growth is based on metathetical reaction with appropriate metal-salts ?ux under mild conditions. Ex-perimentally, zone melting and hydrothermal synthesis methods are all comparatively complex and expensive for growing single crystals, and the ?ux method is at present one of the most economic and convenient meth-ods for mixed anions compounds[16]. In this study, we report the single crystal growth of tungsten oxychloride Li23CuW10O40Cl5in copper chloride (CuCl2, melting point of 498 ℃) flux, and analyze its crystal in details.

1 Experimental

1.1 Materials and methods

The tungsten oxychloride Li23CuW10O40Cl5was synthesized through flux method in open-end quartz tubes. And the synthesis of Li23CuW10O40Cl5adopt a two-step process. Firstly, precursor polycrystalline Li4WO5were synthesized by reacting high-purity reagents in solid- state method. Li2CO3and WO3were mixed with the mole ratio of 2:1. Then these raw materials were placed in a covered alumina crucible and calcinated at 890 ℃ for 12 h as described in reference[17]. Then, single crystal of Li23CuW10O40Cl5was grown from CuCl2flux and pre-cursor Li4WO5. Li4WO5polycrystalline samples and ten times excess CuCl2was loaded into an open-end quartz tube, and put into a vertical pit furnace. The raw mixture was heated at 873 K for 2 d, and then cooling down to 573 K with a cooling rate of 5 K/h before shutting down the furnace.

Finally, the reaction products were washed by hot demineralized water to eliminate the ?uxing agents. After subsequent drying at 353 K, yellow, block shaped single crystals of the desired products were grown and suitable for subsequent single-crystal X-ray diffraction measure-ments.

1.2 Single-crystal structure determination

Block-shaped single crystal of Li23CuW10O40Cl5was selected for single-crystal diffraction measurements. The R-AXIS Spider CCD diffractometer were used to collect data equipped with the graphite monochromated Mo Kradiation (λ=0.071073 nm) at 293 K.

The structure of Li23CuW10O40Cl5was determined through direct method and refined by full-matrix least- squared methods on2with SHELXL package[18]. ADDSYM/PLATON was performed to studied with the final structure for additional symmetry, and no other missed or higher symmetry was found[19]. Crystallo-graphic data (including structure factors) for the struc-tures in this study have been deposited with the Cam-bridge Crystallographic Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK.Copies of the data can be obtained free of charge on quoting the depository numbers CCDC-1952905.

2 Results and discussion

The tungsten oxychloride Li23CuW10O40Cl5synthesized from CuCl2flux in a vertical pit furnace crystallizes hexagonally in space group of P63/mcm with the unit cell parameters of=1.02846(3) nm,=1.98768(9) nm, and=2. There are crystallographically independent five Li, two W, one Cu, two Cl, and five O atoms in the unit cell, respectively, where W(1) atoms are coordinated with one Cl and five O atoms in a distorted octahedra geometry, while W(2) atoms are connected with four O atoms in a tetrahedral coordination. The Cu atoms are connected with six O atoms forming [CuO6] octahedra.

Every two W(2)O4tetrahedra are in reverse symmetry along thedirection (Fig. 1 and 3). Three [W(1)O5Cl] octahedra are connected with each othersharing one Cl atom, and three O atoms with [CuO6] octahedra to form the [W(1)6CuO24Cl2] unit (Fig. 2). The three-dimensional (3D) structure of Li23CuW10O40Cl5is assembled by the [W(1)6CuO24Cl2] units sharing O and Cl atoms with Li. The Li atoms in Li23CuW10O40Cl5present four kinds of environments (Fig. 4): Li(1) atoms are connected with two Cl atoms and four O atoms and Li(2) with one Cl atom and five O atoms, while Li(3) and Li(4) atoms are coordinated with six O atoms, and Li(5) atoms are surrounded by three Cl and four O atoms.

In Li23CuW10O40Cl5, the W?O distances ranging from 0.1778(9) to 0.2154(5) and the bond lengths of W?Cl are 0.2141(5) nm, which are comparable to those in Ba3WO5Cl2[20], K2W3O10[21], WCl6[22], and WOCl4[23], the Cu-O distances are 0.1992(8) nm in good agreement with Ba3Cu2O4Cl2[23], and BaCuSi2O6[24], from bond valence sums (BVS, Table 3) calculations in Li23CuW10O40Cl5, Cu displays +2 formal oxidation states according to charge balance.

The Li?O and Li?Cl distances range from 0.2012(6) to 0.249(3) nm and 0.248(3) to 0.295(4) nm, which are closed to those in Li2MnCl4[25], Li2ZnCl4[26], LiWCl6[27], Li2CaTa2O7[28]. The crystallographic data and structuralrefinements for Li23CuW10O40Cl5are summarized in Table 1.

Fig. 1 View of Li23CuW10O40Cl5 along a direction, the Li atoms are omitted for clarity Cu: blue; W(1): brown; W(2): cyan; Cl: Green; O: red

Fig. 2 [W(1)6CuO24Cl2] unit in Li23CuW10O40Cl5 Cu: blue; W(1): brown; Cl: Green; O: red

Fig. 3 View ofLi23CuW10O40Cl5along c axis, the Li atoms are omitted for clarity Cu: blue; W(1): brown; W(2): cyan; Cl: Green; O: red

Fig. 4 Coordination geometry Li atoms inLi23CuW10O40Cl5 Cl: Green ball; O: red ball; Li: pink ball

Table 1 Summary of crystallographic data and structure refinement parameters for Li23CuW10O40Cl5

,:unit cell dimensions;: volume;number of formula units per unit cell;calcd: calculated density;/mm–1: diffraction wavelength;range: theta range for data collection; GOFon2:Goodness of fit on2(: structure factors);1[>2()] :the residual factor for the observable diffraction point;2[>2()]: the weighted residual factor for the observable diffraction point;1(all data) :the residual factor for all diffraction points;2(all data) : the weighted residual factor for all diffraction points;1= Σ||F| –|F||/Σ|F|,2= Σ[((F2–F2)2)/ Σ[(F2)2]]1/2

Table 2 Atomic coordinates and equivalent isotropic displacement parameters of Li23CuW10O40Cl5

Table 3 Selected bond lengths and atomic BVSfor Li23CuW10O40Cl5

Atomic coordinates and equivalent isotropic displacement parameters are listed in Table 2. Selected bond distances and atomic BVS are displayed in Table 3.

3 Conclusion

In summary, new single crystals Li23CuW10O40Cl5(1) have been successfully grown by flux growth method in open- end silica tubes. The crystal structure of Li23CuW10O40Cl5has been characterized by single crystal diffraction method. The 3D framework is built by [CuO6] octahedra, [W(1)O5Cl] octahedra and [W(2)O4] tetrahedra. The adjacent [W(1)O5Cl] octahedra are connected with each othersharing one Cl atom, and further sharing three O atoms with [CuO6] octahedra to form the [W(1)6CuO24Cl2] unit. The successful synthesis of Li23CuW10O40Cl5through flux-growth method is meaningful for explore new mixed anion compounds in the future work.

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助熔劑法合成鎢氧氯化合物Li23CuW10O40Cl5

李淑芳, 趙爽, 李滿榮

(中山大學 化學學院, 生物無機和合成化學教育部重點實驗室, 廣州 510275)

由于不同陰離子之間的電負性、離子半徑、極化率和氧化態之間的差異, 混合陰離子化合物可以產生不同于單一類型陰離子的新特性。混合陰離子金屬材料在電子、濕度探測器、氣體傳感器、太陽能電池電極等領域有著廣泛的應用前景。助熔劑方法是一種廣泛應用于混合離子晶體生長的方法, 它以適當的金屬鹽作為助熔劑, 在較溫和的條件下進行復分解反應。助熔劑法在混合陰離子化合物的合成中具有重要意義。鎢氧氯化合物Li23CuW10O40Cl5單晶以高質量的Li4WO5為前驅體, 以CuCl2為助熔劑通過兩步法合成。通過X射線單晶衍射確定其晶體結構。結果表明, Li23CuW10O40Cl5結晶屬于P63/mcm空間群, 晶胞參數分別為=1.02846(3) nm,=1.98768(9) nm,=1.82076(11) nm3,=2。單胞中分別包含五個晶體學獨立的Li原子, 兩個W原子, 一個Cu原子, 兩個Cl原子以及五個O原子。結構中, W(1)原子和一個Cl原子及五個O原子相連接, 形成畸變八面體, 而W(2)原子與四個O原子相連接形成四面體, Cu原子與六個O原子相連形成八面體。因此, Li23CuW10O40Cl5的晶體結構主要由[CuO6]和[W(1)O5Cl]八面體以及[W(2)O4]四面體構成。助熔劑法合成鎢氧氯化合物Li23CuW10O40Cl5對今后探索新型的混合陰離子化合物具有重要意義。

鎢氧氯化合物; CuCl2助熔劑; 晶體結構; X射線衍射

TQ174

A

date:2019-11-25;

date: 2020-01-16

National Natural Science Foundation of China (2180153)

LI Shufang (1989–), female, PhD. E-mail: lishufang@mail.sysu.edu.cn

李淑芳(1989–), 女, 博士. E-mail: lishufang@mail.sysu.edu.cn

LI Manrong, professor. E-mail: limanrong@mail.sysu.edu.cn

李滿榮, 教授. E-mail: limanrong@mail.sysu.edu.cn

1000-324X(2020)07-0834-05

10.15541/jim20190598

Li2CO3(Macklin, 99.99%), WO3(Aladdin, 99.99%), and CuCl2(Macklin, 98%).