王 禹,赵海燕,董大朋,于乃森,刘本康,林 翔,王 利

(大连民族大学 物理与材料工程学院,辽宁 大连 116600)

基于1，2-丙二胺配体构筑CuⅡ-LaⅢ异金属修饰型磷钨酸化合物的合成与表征

王 禹,赵海燕*,董大朋,于乃森,刘本康,林 翔,王 利*

(大连民族大学 物理与材料工程学院,辽宁 大连 116600)

在水热条件下, 成功合成了一例新的Cu-La异金属修饰的有机-无机杂化型多金属磷钨酸簇合物[Cu(dap)2]3.5[Cu(dap)2(H2O)]2[La(α-PW11O39)2]·6H2O (1) (dap = 1,2-丙二胺), 并通过元素分析、红外光谱、热分析和X射线单晶衍射对化合物进行了表征和研究. 结构分析表明在化合物1中, 单稀土取代的二聚 [La(α-PW11O39)2]11-单元之间通过[Cu(dap)2]2+阳离子连接, 形成一维Z字型链状结构. 值得注意的是, 化合物1是首例一维含1,2-丙二胺有机配体Cu-La异金属修饰的磷钨酸簇合物.

磷钨酸；异金属的；有机-无机杂化；水热合成技术

Biography： WANG Yu (1995-), male, majoring in polyoxometalate-based functional materials.*Corresponding author, E-mail: Liwangye@dlnu.edu.cn, zhaohaiyan@dlnu.edu.cn.

1 Experimental

1.1 Materials and methods

Na9[A-α-PW9O34]·7H2O were prepared according to the literatures and identified by IR spectra[28]. All other chemicals were obtained from commercial sources and used without further purification. Elemental analyses of C, H and N were carried out with a Vario EL III elemental analyzer. IR spectra (KBr pellets) were recorded on a Thermo Scientific Nicolet iS10 FT-IR Spectrometer over a range of 4 000-400 cm-1. The thermogravimetric (TG) analysis was performed on a METTLER TOLEDO TGA/DSC 1 STARethermal analyzer in the flowing air atmosphere with a heating rate of 10 ℃·min-1from 25 to 1 000 ℃.

1.2 Synthesis of [Cu(dap)2]3.5[Cu(dap)2(H2O)]2[La(α-PW11O39)2]·6H2O(1)

A sample of Na9[A-α-PW9O34]·7H2O ({PW9}) (0.308 g) was stirred in a 0.5 mol/L sodium acetate buffer (pH 4.8, 10 mL), then CuI (0.089 g), La2O3(0.060 g), dap (0.15 mL) and concentrated nitric acid (0.05 mL) were successively added with continuous stirring. The resulting solution was sealed in a 25 mL stainless steel reactor with a Teflon liner and heated at 140 ℃ for 4 d and then cooled to room temperature. Purple block crystals of1were obtained by filtration (yield: 33% based on {PW9}), washed with distilled water and dried in air. Anal. Calcd for1, C33H126Cu5.5LaN22O86P2W22: C 5.83, H 1.87, N 4.53; Found: C 5.71, H 1.99, N 4.41. IR bands (cm-1) for1: 3 451 m, 3 303 m, 3 244 m, 3 141 w, 2 965 w, 2 933 w, 2 897 w, 1 589 vs, 1 460 s, 1 384 vs, 1 090 s, 1 051 s, 944 s, 878 s, 831 m, 780 s, 733 m, 512 m.

1.3 Structure determination

Crystal structure determination by X-ray diffraction was performed on Gemini A Ultra diffractometer with graphite-monochromated Mo Kα(λ= 0.071 073 nm) at 293(2) K. The program SADABS was used for the absorption correction[29]. The structures were solved by the direct method and refined onF2by full-matrix least-squares methods using the SHELX97 program package[30-31]. During the refinement of the two compounds, the command ‘omit 0 50.4’ is used to omit the weak reflection above 50.4 degree. No hydrogen atoms associated with the water molecules were located from the difference Fourier map. The positions of the hydrogen atoms attached to the carbon and nitrogen atoms were geometrically placed. All hydrogen atoms were refined isotropically as a riding mode using the default SHELXTL parameters. All non-hydrogen atoms were refined anisotropically except for some oxygen atoms, carbon atoms and water molecules. The crystallographic data are listed in Table 1. The atomic coordinates and other structural parameters are deposited at the Cambridge Crystallographic Data Centre (No. 1441917; deposit@ccdc.cam.ac.uk).

Table 1 Crystal data and structure refinement for compound 1

2 Results and discussion

2.1 Crystal data and structure discussion

Single-crystal X-ray analysis reveals that1crystallizes in the triclinic space groupP-1. The skeleton of1consists of one dimeric [La(α-PW11O39)2]11-unit with one supporting [Cu1(dap)2]2+cation, two bridging [Cu(dap)2]2+cations (namely, [Cu4(dap)2]2+and [Cu5(dap)2]2+) (Fig. 1a) as well as four discrete copper-dap cations (namely, [Cu2(dap)2(H2O)]2+, [Cu3(dap)2(H2O)]2+[Cu6(dap)2]2+and [Cu7(dap)2]2+), and six lattice water molecules. Bond valence sum calculations[32]indicate that the oxidation states of W, La and Cu in1are +6, +3 and +2, respectively. From the viewpoint of structural chemistry, there exist seven crystallographically dependent Cu2+ions in the molecular structural unit in1. Notably, the site occupancy factor for the Cu1,Cu2, Cu3 and Cu4 cations is 100% while the site occupancy factor of the remaining copper cations (Cu5, Cu6 and Cu7) is 50%. The seven independent copper ions exhibit three types of coordination geometries. The supporting [Cu1(dap)2]2+cation exhibits the square pyramid geometry with four N atoms from two dap ligands (Cu1-N: 0.198 6(13)-0.202 8(11) nm) and one O atom from adjacent [α-PW11O39]9-polyoxoanion (Cu1-O52: 0.233 5(8) nm). Two bridging [Cu(dap)2]2+cations ([Cu4(dap)2]2+and [Cu5(dap)2]2+) cations both adopt the six-coordinate octahedral geometry with four N atoms from two dap ligands (Cu-N: 0.198 3(10)-0.201 9(10) nm) and two O atoms from adjacent [α-PW11O39]9-polyoxoanions (Cu-O: 0.249 8(0)-0.262 7(5) nm). In addition, two discrete [Cu2(dap)2(H2O)]2+and [Cu3(dap)2(H2O)]2+cations both adopt the distorted square pyramid geometry with four nitrogen atoms from two dap ligands [Cu-N: 0.194 2(14)-0.208(3) nm] and a water oxygen atom with the Cu-O distance of 0.248 8(8)-0.258 9(2) nm, whereas the square of another two [Cu6(dap)2]2+and [Cu7(dap)2]2+cations are defined by four nitrogen atoms from two dap ligands with the Cu-N distances of 0.196 4(13)-0.201 7(9) nm. The [La(α-PW11O39)2]11-moiety is constructed from an eight-coordinate LaⅢcation sandwiched by two monovacant [α-PW11O39]7-units, resulting in a well-known sandwich-type bis(undecatungstophospate)lanthanate structure. The La1Ⅲcation exhibits the distorted square antiprism defined by eight vacant O atoms from two [α-PW11O39]7-moieties with La-O distances of 0.246 1(7)-0.252 4(8) nm. Two symmetry-related [La(α-PW11O39)2]11-units are fused togetherviathe [Cu5(dap)2]2+cation constituting the tetrameric building unit (Fig.1b), which consists of four monovacant Keggin [α-PW11O39]7-subunits. Each tetrameric building unit is combined adjacently by two [Cu4(dap)2]2+bridges, giving rise to the interesting 1D zigzag chain-like structure (Fig.1c), which clearly illustrates the connection fashion among the building units. Notably, compound1represents the first 1D dap-containing La-Cu heterometallic phosphotungstate built by dimeric mono-lanthanide-substituted [La(α-PW11O39)2]11-subunits and copper-dap [Cu(dap)2]2+linkers.

As far as we know, analogous dap-containing organic-inorganic hybrid La-Cu-substituted PT [Cu(dap)2(H2O)][Cu(dap)2]3.5[La(α-HPW11O39)2](A) has been isolated[33]. Comparing1withA, three evident differences are observed albeit some similarities exist: (i) the numbers and the site occupancy factors of the CuⅡcenters are different: in1, there exist seven crystallographically dependent Cu2+ions, and the site occupancy factor for the four cations is 100% while the site occupancy factor of the remaining copper cations is 50%; while inA, there are five crystallographically unique CuⅡcations, in which only one with the site occupancy factor of 0.5 and the remaining CuⅡcations all with the site occupancy factor of 1; (ii) although bothAand1contain sandwich Ln-substituted PT fragments and [Cu(dap)2]2+linkers,1exhibits the 1D chain whileAexhibits the 2D sheet architecture. It is worthy to note that compound1represents the first 1D Ln-TM heterometallic phosphotungstate built by mono-lanthanide-substituted sandwich-type units and [Cu(dap)2]2+coordination cations; (iii) from the synthetic point of view, both were hydrothermally synthesized in the presence of organic dap ligands, but the precursors, reaction temperature and time are obviously different:1was obtained at 140 ℃ for 7 d by using La2O3, CuI, concentrated nitric acid and 0.5 mol/L sodium acetate buffer (pH 4.8), whileAwas obtained at 160 ℃ for 6 d by using LaCl3and CuCl2and H2O, which further corroborates that the hydrothermal method is an effective strategy in producing novel Ln-TM heterometallic POMs and the use of different precursors, organic ligands as well as the reaction temperature all play important roles in the synthesis of various charming compounds.

2.2 FT-IR spectroscopy

The IR spectrum of1shows the characteristic vibration patterns resulting from the Keggin framework in the region of 1 090-733 cm-1(Fig. 2). The bands at around 1 090 and 1 051 cm-1can be assigned to the P-O stretching vibration. Compared with that of the parent Keggin anion [PW12O40]3-, the band for the P-O stretching vibration of the polyoxoanions in1splits into two bands because of their lower symmetry than that of the plenary [PW12O40]3-cluster[34]. The W-O stretching vibration bands resulting from the Keggin-type structure, namely,νas(W-Ot),νas(W-Ob-W) andνas(W-Oc-W) appear at 944, 878, 831 and 780, 733 cm-1, respectively. Moreover, the resonances appearing at 3 303-3 141 cm-1and 2 965-2 897 cm-1are attributable to thev(NH2) andv(CH2) stretching vibration while the signals centered at 1 589 and 1 384 cm-1are assigned to theδ(NH2) andδ(CH2) bending vibration, respectively. The occurrence of these characteristic signals confirms the presence of organic dap ligands in1, being in good agreement with the results obtained from X-ray single-crystal structural analyses. In addition, the vibration band centered at 3 451 cm-1implies the presence of lattice water molecules or coordination water molecules. In short, the result of the IR spectrum is in good agreement with the result obtained from X-ray single-crystal structural analysis.

Fig.2 IR spectrum of compound 1

2.3 Thermal analysis

To investigate the thermal stability of1, the TG analyses were performed under flowing dry air atmosphere in the range of 25-1 000 ℃ (Fig.3). TG curve of1exhibits three steps of weight loss between 30 and 800 ℃. The first weight loss is approximately 2.38% between 30 and 235 ℃, attributing to the removal of eight crystal water molecules (calcd. 2.12%). The second weight loss of 4.70% between 235 and 408 ℃ is followed by the decomposition of the partial dap ligands (four dap ligands) (calcd. 4.36%). The third weight loss is 8.03% (calcd. 7.63%) from 408 to 800 ℃, approximately assigned to the decomposition of the remaining seven dap ligands. The observed experimental values are approximately consistent with the theoretical values.

Fig.3 Thermogravimetric curve of compound 1

3 Conclusion

In summary, we have hydrothermally synthesized a new copper-lanthanide heterometallic organic-inorganic hybrid polyoxotungstate [Cu(dap)2]3.5[Cu(dap)2(H2O)]2[La(α-PW11O39)2]·6H2O (1) and structurally characterized by IR spectrum, elemental analysis, TGA and single-crystal X-ray diffraction. The connectivity between the dimeric mono-La substituted Keggin [La(α-PW11O39)2]11-subunits and Cu(dap)2]2+linkers further produces the scare 1D zigzag chain architecture. Although the connection of amine is an effective strategy to make the extended structure, it is still great opportunities and challenges in exploring and making the extended organic-inorganic hybrid POM derivatives.

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date： 2017-04-20.

SynthesisandcharacterizationofaCuⅡ-LaⅢheterometallicphosphotungstatecontaining1,2-diaminopropaneligand

WANG Yu, ZHAO Haiyan*, DONG Dapeng, YU Naisen, LIU Benkang, LIN Xiang, WANG Li*

(SchoolofPhysicsandMaterialsEngineering,DalianMinzuUniversity,Dalian116600,Liaoning,China)

A new organic-inorganic hybrid phosphotungstate-based copper-lanthanide heterometallic derivative [Cu(dap)2]3.5[Cu(dap)2(H2O)]2[La(α-PW11O39)2]·6H2O (1) (dap = 1,2-diaminopropane) has been prepared under hydrothermal conditions and characterized by elemental analysis, infrared spectroscopy, thermogravimetric (TG) analysis and X-ray single-crystal diffraction. Structural analysis indicates that1exhibits a special one-dimensional zigzag chain structure constructed from mono-lanthanide-substituted 1∶2-type [La(α-PW11O39)2]11-moieties and [Cu(dap)2]2+linkers. Notably, compound1represents the first 1D dap-containing La-Cu heterometallic phosphotungstate.

phosphotungstate; heterometallic; organic-inorganic hybrid; hydrothermal technique

O614DocumentcodeA

1008-1011(2017)05-0568-07

Supported by the Natural Science Foundation of China (21501021 and 11474045), the 2014 Program for Liaoning Excellent Talents in University (LJQ2014138) and the Program for Key Laboratory of Photochemical Conversion and Optoelectronic Materials, TIPC, CAS (PCOM201708).

Nowadays, considerable attention has been directed toward exploitation of inorganic-organic hybrid materials based on polyoxometalates (POMs) because of their wide range of size, tunability, composition, intriguing architectures as well as their potential applications in magnetism, photochemistry, catalysis and sensitive devices[1-6]. Among them, lacunary Keggin polyoxotungstate (POT) precursor, an important ramification in the POM chemistry, can often work as versatile polydentate inorganic ligands to “capture” lanthanide (Ln) or transition-metal (TM) cations in the present of organic ligands owing to the easy accessibility of POT precursor, the structural diversities of POT units derived from the self-assembly of simple materials[7-9]. In the past several years, comparing the wide study and tremendous number of organic-inorganic hybrid TM or Ln-substituted Keggin POTs[10-13], novel organic-inorganic hybrid TM-Ln heterometallic Keggin-type POTs have only been explored to a limited extent[14-16], for instance, a series of tungstoantimonate-based TM-Ln heterometallic hybrids [Ln(H2O)8]2[Fe4(H2O)8(thr)2][B-β-AsW9O33]2(Ln = LaⅢ, PrⅢ, NdⅢ, SmⅢ, EuⅢ, GdⅢ, TbⅢ, DyⅢ, ErⅢ; thr = threonine)[17], two 1-D Cu-bridged tetrahedral nanoclusters [Cu(en)2]5[Cu(en)2(H2O)]2[Ln4Ge4W46O164(H2O)3]10-(Ln = GdⅢ, YⅢ; en = 1,2-ethylenediamine)[18], one scare 3D framework [Ce2(ox)3(H2O)2]2{[Mn(H2O)3]2[Mn4(GeW9O34)2(H2O)2]8-(ox = oxalate)[19], a series of 3D hybrids [Cu2.5(bimpy)2(H2O)2][Ln(H2O)3(α-SiW11O39)] (Ln = EuⅢ, SmⅢ, HoⅢ, YⅢ, CeⅢ; bimpy = 3,5-bis(1-imidazolyl)pyridine)[20], an unprecedented [{CeIV(OAc)}CuⅡ3(H2O)(B-α-GeW9O34)2]11-[21], a single-molecule magnet Na2[(A-β-SiW9O34)2CeIV4O2(OAc)2][(A-β-SiW9O34)MnⅢ3MnIVO3(OAc)3]2}20-[22], and so on. It can be found that investigations on organic-inorganic hybrid TM-Ln-PTs (PT = phosphotungstates) are comparatively rare, including: Ac-en-containing Na2[Cu(en)2(H2O)]4[Sm(α-PW11O39)(OAc)(H2O)]2[23]; ox-en-containing [Cu(en)2(H2O)][Cu(en)2][Tb(α-PW11O39)(H2O)2(ox)Cu(en)][24]; bpy-en-containing {[Cu(en)2]1.5[Cu(en)(bpy)]Nd[(α-H5PW11O39)2]}3-(bpy = 2,2′-bipyridine)[25]; bpy-ox-containing [{Ln(PW11O39)2}{Cu2(bpy)2(μ-ox)}]9-(Ln = La, Pr, Eu, Gd, Yb)[26], en-containing [Cu(en)2]2H6[Ce(α-PW11O39)2] as well as dap-containing [Cu(dap)2(H2O)][Cu(dap)2]4.5[Dy(α-PW11O39)2][27](dap = 1,2-diaminopropane). As a result, the search and exploration of novel organic-inorganic hybrid TM-Ln-containing PTs are still an incipient field. Under this background, we began to explore this challengeable area.

In this work, we successfully obtained a new inorganic-organic hybrid copper-lanthanide heterometallic Keggin-type phosphotungstate [Cu(dap)2]3.5[Cu(dap)2(H2O)]2[La(α-PW11O39)2]·6H2O (1) hydrothermally. Moreover, it was structurally characterized by X-ray single-crystal diffraction, elemental analysis, infrared spectroscopy and X-ray powder diffraction. Furthermore, the thermogravimetric analysis was also investigated.

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