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首页> 外文期刊>Chemistry: A European journal >Reactivity of polyoxoniobates in acidic solution: Controllable assembly and disassembly based on niobium-substituted germanotungstates
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Reactivity of polyoxoniobates in acidic solution: Controllable assembly and disassembly based on niobium-substituted germanotungstates

机译：聚氧杂酸盐在酸性溶液中的反应性：基于铌取代的锗钨酸盐的可控组装和拆卸

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摘要

The reactivity of polyoxoniobates has been studied in acidic solution by grafting niobium onto trivacant Keggin-type germanotungstates. Four niobium-containing compounds were obtained in the course of this study. Cs _(6.5)K_(0.5)[GeW_9(NbO_2)_3O _(37)]·6H_2O (Cs_(6.5)K_(0.5)-1) synthesized by the reaction of K_7H[Nb_6O_(19)] and A-α-Na_(10)[GeW_90_(34)] in H_2O _2 solution is a tris(peroxoniobium)-substituted A-α-GeW _9 derivative. Cs_(6.5)K_(0.5)[GeW_9Nb _3O_(40)]· 10H_2O (Cs_(6.5)K _(0.5)-2) is a peroxo-free compound obtained by eliminating the peroxo groups in 1. Monomers 1 and 2 as precursors can each afford two nanoscale POMs, dimer Cs_5[H_(15)Ge_2W_(18)Nb _8O_(88)]·18H_2O (Cs_5-3) and tetramer Cs_8K_3H_9[Ge_4W _(36)Nb_(16)O_(166)]· 27H_2O (Cs _8K_3H_9-4), through the formation of Nb-O-Nb bridges. Disassembly through the cleavage of Nb-O-Nb bonds from 4 to 2 and 1 was achieved by controlling the pH and by adding H_2O_2, respectively. The transition from 1 to 2 can be achieved by simply adding H _2O_2 to a solution of 1. All four compounds were characterized in the solid state by elemental analysis, infrared spectroscopy, thermogravimetry, and single-crystal X-ray diffraction. ~(183)Wa NMR analysis proved that the solid-state structures of polyanions 1-4 were retained after dissolution. Disassembly from 4 to 1 and 2 in solution was observed by ~(183)Wa NMR spectroscopy. The UV/Vis spectra of 1 at different pH confirmed that it is stable in the pH range of 0.1-14.0 at room temperature. Nanoscale polyoxometalates: The reactivity of polyoxoniobates has been studied in acidic solution by grafting niobium onto trivacant Keggin-type germanotungstates. Monomer 1 or 2 afforded two nanoscale polyoxometalates, dimer 3 and tetramer 4, through the formation of Nb-O-Nb bridges. Disassembly based on the cleavage of Nb-O-Nb bonds was achieved by controlling the pH or by adding H_2O_2 (see figure).
机译：通过将铌接枝到三空Keggin型锗钨酸盐上，研究了在酸性溶液中聚氧杂酸盐的反应性。在本研究过程中获得了四种含铌化合物。通过K_7H [Nb_6O_（19）]与A-α反应合成的Cs _（6.5）K_（0.5）[GeW_9（NbO_2）_3O _（37）]·6H_2O（Cs_（6.5）K_（0.5）-1） H_2O _2溶液中的-Na_（10）[GeW_90_（34）]是三（过氧铌）取代的A-α-GeW_9衍生物。 Cs_（6.5）K_（0.5）[GeW_9Nb _3O_（40）]·10H_2O（Cs_（6.5）K _（0.5）-2）是通过消除1中的过氧基而获得的无过氧化合物。前体均可以提供两个纳米级POM，二聚体Cs_5 [H_（15）Ge_2W_（18）Nb _8O_（88）]·18H_2O（Cs_5-3）和四聚体Cs_8K_3H_9 [Ge_4W _（36）Nb_（16）O_（166）] ·通过形成Nb-O-Nb桥形成27H_2O（Cs _8K_3H_9-4）。通过控制pH值和分别加入H_2O_2，可以实现Nb-O-Nb键从4至2和1的裂解。从1到2的转变可以通过简单地将H _2O_2添加到1的溶液中来实现。所有四种化合物均通过元素分析，红外光谱，热重分析和单晶X射线衍射表征为固态。 〜（183）Wa NMR分析证明聚阴离子1-4的固态结构在溶解后得以保留。通过〜（183）Wa NMR光谱观察到溶液中从4至1和2的分解。 1在不同pH值下的UV / Vis光谱证实，它在室温下在0.1-14.0的pH范围内是稳定的。纳米级多金属氧酸盐：已通过将铌接枝到三空的Keggin型锗钨酸盐上，研究了酸性条件下多金属氧酸盐的反应性。单体1或2通过形成Nb-O-Nb桥提供了两种纳米级多金属氧酸盐，即二聚物3和四聚物4。通过控制pH值或添加H_2O_2，可实现基于Nb-O-Nb键断裂的分解（见图）。

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