Syntheses, Crystal Structures, and Properties of Six New Lanthanide(III) Transition Metal Tellurium(IV) Oxyhalides with Three Types of Structures

Solid-state reactions of lanthanide(III) oxide (and lanthanide(III) oxyhalide), transition metal halide (and transition
metal oxide), and TeO2 at high temperature lead to six new lanthanide transition metal tellurium(IV) oxyhalides with
three different types of structures, namely, DyCuTe2O6Cl, ErCuTe2O6Cl, ErCuTe2O6Br, Sm2Mn(Te5O13)Cl2, Dy2Cu(Te5O13)Br2, and Nd4Cu(TeO3)5Cl3. Compounds DyCuTe2O6Cl, ErCuTe2O6Cl, and ErCuTe2O6Br are isostructural.
The lanthanide(III) ion is eight-coordinated by eight oxygen atoms, and the copper(II) ion is five-coordinated by four
oxygens and a halide anion in a distorted square pyramidal geometry. The interconnection of Ln(III) and Cu(II) ions
by bridging tellurite anions results in a three-dimensional (3D) network with tunnels along the a-axis; the halide
anion and the lone-pair electrons of the tellurium(IV) ions are oriented toward the cavities of the tunnels. Compounds
Sm2Mn(Te5O13)Cl2 and Dy2Cu(Te5O13)Br2 are isostructural. The lanthanide(III) ions are eight-coordinated by eight
oxygens, and the divalent transition metal ion is octahedrally coordinated by six oxygens. Two types of polymeric
tellurium(IV) oxide anions are formed:  Te3O84- and Te4O104-. The interconnection of the lanthanide(III) and divalent
transition metal ions by the above two types of polymeric tellurium(IV) oxide anions leads to a 3D network with
long, narrow-shaped tunnels along the b-axis. The halide anions remain isolated and are located at the above
tunnels. Nd4Cu(TeO3)5Cl3 features a different structure. All five of the Nd(III) ions are eight-coordinated (NdO8 for
Nd(1), Nd(2), Nd(4), and Nd(5) and NdO7Cl for Nd(3)), and the copper(I) ion is tetrahedrally coordinated by four
chloride anions. The interconnection of Nd(III) ions by bridging tellurite anions resulted in a 3D network with large
tunnels along the b-axis. The CuCl4 tetrahedra are interconnected into a 1D two-unit repeating (zweier) chain via
corner-sharing. These 1D copper(I) chloride chains are inserted into the tunnels of the neodymium(III) tellurite via
Nd−Cl−Cu bridges. Luminescent studies show that ErCuTe2O6Cl and Nd4Cu(TeO3)5Cl3 exhibit strong luminescence
in the near-IR region. Magnetic measurements indicate the antiferromagnetic interactions between magnetic centers
in these compounds.

以镧系(III)氧化物（及镧系(III)氧卤化物）、过渡金属卤化物（及过渡金属氧化物）与二氧化碲（TeO₂）在高温下发生固相反应，成功制备出六种新型镧系过渡金属碲(IV)氧卤化物，它们分属三种不同结构类型，分别为DyCuTe₂O₆Cl、ErCuTe₂O₆Cl、ErCuTe₂O₆Br、Sm₂Mn(Te₅O₁₃)Cl₂、Dy₂Cu(Te₅O₁₃)Br₂及Nd₄Cu(TeO₃)₅Cl₃。
其中DyCuTe₂O₆Cl、ErCuTe₂O₆Cl与ErCuTe₂O₆Br为同构化合物。该结构类型中，镧系(III)离子由8个氧原子实现八配位，铜(II)离子则由4个氧原子与1个卤离子配位，形成畸变四方锥几何构型，配位数为5。通过桥连亚碲酸盐阴离子连接Ln(III)与Cu(II)离子，可得到沿a轴方向带有孔道的三维（3D）网络结构；卤离子与碲(IV)离子的孤对电子朝向该孔道空腔。
Sm₂Mn(Te₅O₁₃)Cl₂与Dy₂Cu(Te₅O₁₃)Br₂亦为同构化合物。此类结构中，镧系(III)离子为八氧配位，二价过渡金属离子则以6个氧原子形成八面体配位。体系中存在两种聚合态碲(IV)氧化物阴离子：Te₃O₈⁴⁻与Te₄O₁₀⁴⁻。通过上述两种聚合态碲(IV)氧化物阴离子桥连镧系(III)与二价过渡金属离子，可得到沿b轴方向带有狭长型孔道的三维网络结构；孤立的卤离子位于该孔道之中。
Nd₄Cu(TeO₃)₅Cl₃则具有独特的不同结构。该化合物中全部5个Nd(III)离子均为八配位：Nd(1)、Nd(2)、Nd(4)与Nd(5)为NdO₈配位，Nd(3)为NdO₇Cl配位；铜(I)离子由4个氯离子配位，形成四面体构型。通过桥连亚碲酸盐阴离子连接Nd(III)离子，可得到沿b轴方向带有大尺寸孔道的三维网络结构。CuCl₄四面体通过顶点共享连接，形成具有两个结构单元重复的一维（zweier）链。此类一维氯化亚铜链通过Nd−Cl−Cu桥键嵌入至钕(III)亚碲酸盐的孔道结构中。
发光性能测试表明，ErCuTe₂O₆Cl与Nd₄Cu(TeO₃)₅Cl₃在近红外区域展现出较强的发光行为。磁性测试结果显示，此类化合物的磁中心之间存在反铁磁相互作用。