Synthesis and characterization of a novel inorganic-organic hybrid heteropolymolybdate constructed by transition-metal (NiII)

SUN Lin,LIU Yun,LI Jie

(College of Chemistry and Chemical Engineering,Henan University,Kaifeng 475004,Henan,China)

Abstract: One novel heteropolymolybdate, · 9H2O (1) (dien = diethylenetriamine),constructed from the new fragment [AsVMo10O36]9- and four transition metal complexes has been synthesized under the hydrothermal condition and characterized by the elemental analysis,IR spectroscopy and single-crystal X-ray diffraction. Structurally 1 resembles an infrequent lacunary structure like an open basket,which derives from the famous Keggin structure by removing two edge-sharing MoO6 octahedra.

Keywords: heteropolymolybdate; lacunary structure; Keggin

CLCnumber：O614Documentcode：A

ArticleID：1008-1011(2020)04-0312-06

Receiveddate：2020-04-01.

Biography：SUN Lin (1989-)，female，associate professor，research field: polyoxomolybdate chemistry.*Corresponding author,E-mail：lllijie2007@henu.edu.cn.

孫 琳，劉 云，李 杰*

(河南大學(xué) 化學(xué)化工學(xué)院,河南 開封 475004)

關(guān)鍵詞：雜多鉬酸鹽；缺位結(jié)構(gòu)；Keggin

Polyoxometalates (POMs) are well-known inorganic metal oxide clusters possessing unmatched physical and chemical properties that allow them to have signicant applications in catalysis,electronics,magnetism,optics,medicine,etc[1-5]. Organic ligands can induce the POMs,as excellent inorganic ligands or noncoordinated templates due to their abundant O atoms,to form various packing arrangements in the final hybrid materials via covalent bond or weak intermolecular interaction[6-9]. These interactions between POMs and organic ligands play important roles in the stabilization of hybric aggregates[6].Moreover,the synergic effect between organic and inorganic components will lead to composite properties or even new characters. Thus,the organic moieties are important factors in adjusting the structures and characters of inorganic-organic hybrid compounds. The N-donor rigid ligand with smaller steric hindrance is widely applied as bi-/tri-dentate linkers to construct hybrid materials[7-10]. It can provide flexible bonding positions and good fitting for the coordination ways of metal ions. In addition,the transition metal ions have outstanding coordination abilities with both surface oxygen atoms of POM and nitrogen atoms of organic ligands,which will provide vital ligaments between POMs and various organic ligands to construct the inorganic-organic hybrid.

1 Experiment

1.1 Materials and physical measurements

All chemicals are commercially obtained and used as purchased without further purification. Elemental analyses (C,H,and N) were recorded using a PerkineElmer 2400-II CHNS analyzer. IR spectroscopy were performed using a solid sample palletized with KBr on a Bruker VERTEX 70 IR spectrometer ranging from 400 cm-1to 4 000 cm-1.

1.2 Preparation of 1

A mixture of Na2MoO4· 2H2O (0.50 g,2.0 mmol),As2O3(0.12 g,0.6 mmol),Ni(NO3)3· 6H2O (0.35 g,1.2 mmol),1,10-phenanthroline (0.04 g,0.2 mmol),dien (0.2 mL),and water (15 mL) was stirred and its pH value was adjusted to 5.92 with glacial acetic acid. The resulting suspension was sealed in a 20 mL Teflon-lined reactor and kept at 160 ℃ for five days. After cooling the autoclave to room temperature,black block single crystals of1were separated,washed with water,and air-dried (14% yield based on As element). C,H and N elemental analysis for C16H48AsMo10N12Ni4O45: calcd. (%): C,8.01; N,7.01; H,2.02. Found (%): C,8.10; N,7.08; H,1.96.

1.3 X-ray crystallographic determination

Crystallographic data were collected with a Bruker Smart APEX-II CCD diffractometer with graphite-monochromated Mo Kαradiation (λ= 0.071 073 nm). The structure was solved by direct methods and refined by full-matrix least squares onF2using the SHELXTL-97 package[22]. The finalR= 0.037 4,wR= 0.105 6 (w=1/[σ(Fo) +(0.055 3P)2+ 115.328 6P],whereP= (Fo2+ 2Fc2)/3). The maximum and minimum peaks on the final difference Fourier map were 2.27 and -850 e·nm-3,respectively. In the final refinement cycles,the Mo,As,and Ni atoms were refined anisotropically; the O,C and N atoms were refined isotropically. No hydrogen atoms associated with water molecules were located from the difference Fourier map,and all H atoms on water molecules were directly included in the molecular formula. CCDC-1007238. Crystallographic data for1is summarized in Table 1. The selected bond lengths for1are listed in Table 2.

Table 1 Crystal data and structural refinements for 1

Table 2 Selected bond lengths in 1

2. Results and discussion

2.1 Structural description

Fig.1 Polyhedral/ball-stick representation of lacunary unit 1a in 1. The hydrogen atoms and free water molecules are omitted for clarity

Four NiIIcations are coordinated by three N atoms from a dien ligand [Ni-N 0.219 6(5)-0.209 7(6) nm] and three O atoms from the dilacunary polyanion {AsMo10} [Ni-O 0.204 3(4)-0.219 6(5) nm] tonish a distorted octahedral geometry.

The bond valence sum (BVS) calculations[25]indicate that the As atom is in the +5 oxidation state,all Ni atoms +2 oxidation state,and all Mo sites are in the +6 oxidation state,however,that of the Mo3 is +5 (Table 3). This result is in good agreement with arsenical usual geometric configuration. Notably,only As2O3was used as the starting material; however,the AsVelement was observed in the products. Therefore,part of As2O3reactants must have been oxidized in the reaction. Similar phenomenon can be observed in previous literature reports[26].

Table 3 BVS values for As,Ni,Mo and O atoms in 1

2.2 FT-IR spectroscopy

Fig.2 IR spectrum of 1

3 Conclusion