Composition Space Analysis in the Development of Copper Molybdate Hybrids Decorated by a Bifunctional Pyrazolyl/1,2,4-Triazole Ligand

A bitopic ligand, 4-(3,5-dimethylpyrazol-4-yl)-1,2,4-triazole
(Hpz-tr) (1), containing two different
heterocyclic moieties was employed for the design of copper­(II)–molybdate
solids under hydrothermal conditions. In the multicomponent CuII/Hpz-tr/MoVI system, a diverse
set of coordination hybrids, [Cu­(Hpz-tr)2SO4]·3H2O (2), [Cu­(Hpz-tr)­Mo3O10] (3), [Cu4(OH)4(Hpz-tr)4Mo8O26]·6H2O (4), [Cu­(Hpz-tr)2Mo4O13] (5), and [Mo2O6(Hpz-tr)]·H2O (6), was prepared and characterized.
A systematic investigation of these systems in the form of a ternary
crystallization diagram approach was utilized to show the influence
of the molar ratios of starting reagents, the metal (CuII and MoVI) sources, the temperature, etc., on the reaction
products outcome. Complexes 2–4 dominate
throughout a wide crystallization range of the composition triangle,
while the other two compounds 5 and 6 crystallize
as minor phases in a narrow concentration range. In the crystal structures
of 2–6, the organic ligand behaves
as a short [N–N]-triazole linker between metal centers Cu···Cu
in 2–4, Cu···Mo in 5, and Mo···Mo in 6, while the
pyrazolyl function remains uncoordinated. This is the reason for the
exceptional formation of low-dimensional coordination motifs: 1D for 2, 4, and 6 and 2D for 3 and 5. In all cases, the pyrazolyl group is involved
in H bonding (H-donor/H-acceptor) and is responsible for π–π
stacking, thus connecting the chain and layer structures in more complicated
H-bonding architectures. These compounds possess moderate thermal
stability up to 250–300 °C. The magnetic measurements
were performed for 2–4, revealing
in all three cases antiferromagnetic exchange interactions between
neighboring CuII centers and long-range order with a net
moment below Tc of 13 K for compound 4.

本研究选用含两种不同杂环结构的双位点配体（bitopic ligand）4-(3,5-二甲基吡唑-4-基)-1,2,4-三唑（Hpz-tr）(1)，在水热条件下构建铜(II)-钼酸盐固态材料。在多组分CuII/Hpz-tr/MoVI体系中，成功制备并表征了一系列配位杂化物：[Cu(Hpz-tr)2SO4]·3H2O(2)、[Cu(Hpz-tr)Mo3O10](3)、[Cu4(OH)4(Hpz-tr)4Mo8O26]·6H2O(4)、[Cu(Hpz-tr)2Mo4O13](5)与[Mo2O6(Hpz-tr)]·H2O(6)。本研究采用三元结晶相图（ternary crystallization diagram）系统探究该体系，考察了起始反应物摩尔比、金属（CuII与MoVI）源、反应温度等因素对反应产物分布的影响。配合物2~4在组成三角的宽结晶区间内占据主导地位，而化合物5与6仅在窄浓度范围内以次要晶相形式析出。在配合物2~6的晶体结构中，有机配体作为[N–N]桥联的三唑短连接体，在2~4中连接Cu···Cu金属中心，在5中连接Cu···Mo金属中心，在6中连接Mo···Mo金属中心，而吡唑基官能团始终未参与配位。这一结构特征促成了独特的低维配位基元的形成：配合物2、4、6为一维结构，配合物3、5为二维结构。所有配合物中的吡唑基均参与氢键作用（作为氢键给体/受体），并通过π-π堆积相互作用，将一维链与二维层结构组装为更复杂的氢键骨架体系。上述化合物具有中等热稳定性，可稳定至250~300 ℃。对配合物2~4开展了磁性表征测试，结果显示三种配合物中相邻CuII中心均存在反铁磁交换相互作用，其中化合物4在低于13 K的临界温度（Tc）下呈现长程有序并产生净磁矩。