Abstract：A novel triclinic polyoxosilicotungstate [Cu(en)2(H2O)]n{[Cu(en)2] [SiW12O39.5]}n(OH)n·n(en) was hydrothermally synthesized with P1 space group and a one-dimensional double chains structure. The hydrogen bonds between ligands and cluster anions formed a two-dimensional layered structure. The layers were connected to form a three-dimensional supramolecule by strong hydrogen bonds between free en molecules, hydroxyls and cluster anions. The compound was characterized by XRD, FTIR, two-dimensional(2D) correlation infrared spectroscopy under magnetic and thermal perturbation, UV-Vis DRS spectrum and TG etc. XRD showed that the spectrum was basically consistent with the simulation by single crystal structure data, and the main peaks were the same, indicating that the synthesized compound was relatively pure. The FT-IR spectrum indicated that there was four characteristic stretching vibration of Keggin cluster anion skeleton in the range of 1100 to 700 cm-1, the νas(O—H) at 3 600～3 300 cm-1 was broadened due to the formation of hydrogen bonds. Furthermore, the two-dimensional infrared correlation spectroscopy under 5~50 mT magnetic showed that the strong response peaks at 890，800 and 780 cm-1 were νs(W═Od)，ν(W—Ob—W) and ν(W—Oc—W) respectively. This might be caused by the coordination between magnetic Cu and Od of cluster anion, which led to the variation of the dipole moment of W—O skeleton stretching vibration with magnetic. The 2D-IR COS under 50~120 ℃ illustrated that there was a strong νas(W═Od) response peak at 920 cm-1, while ν (W—Ob—W) at 762 cm-1 and ν(W—Oc—W) at 748 cm-1 was relatively weak, which verified that the hydrogen bonds formed by Od were more than those of Ob in the structural analysis. The strong hydrogen bonding made the whole cluster anion skeleton more sensitive to the thermal response. UV-Vis DRS found the Oμ→W(LMCT) and d→d transition of Cu2+ happened at 309 and 558 nm respectively. TGA showed that the weight loss process could be divided into three stages. In the first stage, the free en and hydroxyl groups were lost, and in the second, the coordinated en and coordination water was lost. At last, in the third stage, the framework of the tungsten oxide cluster began to collapse from 540 ℃. The complex reaction of the compound and RhB under different pH conditions were performed and discussed. The results showed that strong acid condition was more favorable for the complex reaction and the formation of the purple complex. The standard concentration curve of RhB was drawn under pH 1, and the absorbance of residual RhB in the test solution after the complex reaction was detected by UV-Vis. Through further calculation, the best ratio of RhB to the compound was determined as 4∶1. This research provided a novel way to remove organic pollutant RhB from industrial wastewater and revealed the potential application prospects of the compound.
Key words：Polyoxosilicotungstate; Keggin structure; Two dimensional infrared correlation spectral; The complex
孙瑞卿，石 林，陈义平，孙燕琼. 硅钨酸晶体合成和谱学研究及与罗丹明B复合反应探索[J]. 光谱学与光谱分析, 2021, 41(08): 2455-2461.
SUN Rui-qing, SHI Lin, CHEN Yi-ping, SUN Yan-qiong. Syntheses and Spectral Study of the Polyoxosilicotungstate and Its Complex Reaction With RhB. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2021, 41(08): 2455-2461.
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