Chen Lijuan, Zhang Fang, Ma Xing, Luo Jie, Zhao Junwei
Henan Key Laboratory of Polyoxometalate Chemistry, Institute of Molecular and Crystal Engineering, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004, P. R. China.
Dalton Trans. 2015 Jul 28;44(28):12598-612. doi: 10.1039/c5dt00696a.
Two classes of novel tetra-iron substituted sandwich-type arsenotungastates (ATs) with supporting lanthanide (Ln) pendants KNa2 [Ln(H2O)7][Fe4(H2O)10(B-β-AsW9O33)2]·21H2O [Ln = La(III) (1), Pr(III) (2), Nd(III) ()3, Sm(III) (4)] and [Ln(H2O)8]2[Fe4(H2O)8(l-thr)2(B-β-AsW9O33)2]·20H2O [Ln = La(III) (5), Pr(III) ()6, Nd(III) (7), Sm(III) (8), Eu(III) (9), Gd(III) (10), Tb(III) (11), Dy(III) (12), Er(III) (13)] (l-thr = l-threonine) have been synthesized by the hydrothermal reaction of the As2W19O67(H2O) precursor with Fe(3+) cations and Ln(3+) cations in the presence of l-thr or l-leucine and l-alanine, and further characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. Structural analyses indicate that 1-4 display the inorganic 2-D sheet architecture constructed from tetra-iron sandwiched AT Fe4(H2O)10(B-β-AsW9O33)2 fragments by bridging Ln(H2O)7 cations whereas the molecular structures of the isostructural 5-13 consist of an organic-inorganic hybrid tetra-iron substituted sandwich-type AT Fe4(H2O)8(l-thr)2(B-β-AsW9O33)2 fragment and two pendant Ln(H2O)8 cations. As far as we know, 1-4 represent the rare inorganic 2-D extended ATs based on transition-metal substituted sandwich-type polyoxometalate units and Ln linkers and 5-13 are the first Fe-Ln heterometallic ATs with amino acid ligands. The solid state photoluminescence (PL) measurements of 9 and 11 have been performed at room temperature. The PL emission of 9 is mainly derived from the characteristic (5)D0 → (7)F2 (J = 4-0) transitions of the Eu(III) cations whereas the PL behavior of 11 stems from the common contribution of the (5)D4 → (7)FJ (J = 5-3) transitions of the Tb(III) ions and oxygen-to-metal (O → W) charge-transfer transitions of AT segments. The thermogravimetric (TG) analyses of 1-4 and 6-12 have been investigated.
通过[As₂W₁₉O₆₇(H₂O)]¹⁴⁻前体与Fe³⁺阳离子和Ln³⁺阳离子在L-苏氨酸或L-亮氨酸及L-丙氨酸存在下进行水热反应，合成了两类新型的带有镧系（Ln）侧基的四铁取代夹心型砷钨酸盐（ATs），即KNa₂[Ln(H₂O)₇][Fe₄(H₂O)₁₀(B-β-AsW₉O₃₃)₂]·21H₂O [Ln = La(III) (1)，Pr(III) (2)，Nd(III) (3)，Sm(III) (4)] 和 [Ln(H₂O)₈]₂[Fe₄(H₂O)₈(l-thr)₂(B-β-AsW₉O₃₃)₂]·20H₂O [Ln = La(III) (5)，Pr(III) (6)，Nd(III) (7)，Sm(III) (8)，Eu(III) (9)，Gd(III) (10)，Tb(III) (11)，Dy(III) (12)，Er(III) (13)]（l-thr = L-苏氨酸），并通过元素分析、红外光谱和单晶X射线衍射对其进行了进一步表征。结构分析表明，1 - 4呈现出由四铁夹心的AT [Fe₄(H₂O)₁₀(B-β-AsW₉O₃₃)₂]⁶⁻片段通过桥连[Ln(H₂O)₇]³⁺阳离子构建的无机二维片状结构，而异构的5 - 13的分子结构由有机 - 无机杂化的四铁取代夹心型AT [Fe₄(H₂O)₈(l-thr)₂(B-β-AsW₉O₃₃)₂]⁶⁻片段和两个侧基[Ln(H₂O)₈]³⁺阳离子组成。据我们所知，1 - 4代表了基于过渡金属取代夹心型多金属氧酸盐单元和Ln连接体的罕见无机二维扩展ATs，5 - 13是首批带有氨基酸配体的Fe - Ln异金属ATs。已在室温下对9和11进行了固态光致发光（PL）测量。9的PL发射主要源自Eu(III)阳离子的特征(⁵)D₀ → (⁷)F₂ (J = 4 - 0)跃迁，而11的PL行为源于Tb(III)离子的(⁵)D₄ → (⁷)F_J (J = 5 - 3)跃迁和AT片段的氧到金属（O → W）电荷转移跃迁的共同贡献。已对1 - 4和6 - 12进行了热重（TG）分析。
