组氨酸12-硅钨杂多酸盐超分子化合物的结构与光致变色性质

摘要

We synthesized a novel histidine salt of 12-silicotungstate supramolecular compound ((HisH2)2 SiW12O40·6H2O) by a solution method.Its composition, thermostability, and structure were characterized by elemental analysis, thermal gravimetric and differential thermal analysis (TG-DTA), and single crystal X-ray diffraction, respectively.The experimental results show that the supramolecular compound has a composition of C12H34N6O50SiW12 and it is stable under 135 °C in air.It belongs to a monoclinic system (space group C2/c) with a=2.44005(18) nm, b=1.29788(10) nm, c=1.86898(14) nm, β=124.0380(10)°, V= 4.9048(6) nm3, Z=4, and Dc=4.465 g·cm-3.The final statistics based on F2 are goodness-of-fit (GOF) = 1.268, R1=0.0344 and wR2=0.0851 for (I＞2σ(I)).X-ray diffraction analysis further reveals that this supramolecular compound mainly consists of polyoxometalate anions [SiW12O40]4-, protonated histidine cations [HisH2]2+ and lattice water.A three-dimensional (3D) network is formed through hydrogen bonding.The resulting sample shows photochromism under UV irradiation.We propose a possible photochromic mechanism by an analysis of the chromic sample’s electron spin resonance (ESR) spectrum.%通过溶液法合成了一个新颖的组氨酸12-硅钨杂多酸盐((HisH2)2SiW12O40·6H2O)单晶超分子化合物.利用元素分析、热重-差热分析和X射线单晶衍射测试分别对其组成、热稳定性和结构进行了表征.实验结果表明:该超分子化合物的组成为C12H34N6O50SiW12.空气中,在135℃以下稳定.它属于单斜晶系(空间群为C2/C),晶胞参数为a=2.44005(18)nm,b=1.29788(10)nm,c=1.86898(14)nm,β=124.0380(10)°,V=4.9048(8)nm3,Z=4和Dc=4.465 g·cm-3.基于F2的最终统计:拟合优度(GOF)=1.268,R1=0.0344和wR2=0.0851(1>2σ(1)).该单晶超分子化合物的基本结构单元由一个[SiW12O40]4-多阴离子和两个质子化的[H2HiS]2+有机阳离子以及结晶水组成.他们之间通过氢键的作用组装成三维网络结构.在紫外光照射下,样品具有光致变色性质.通过对变色样品电子自旋共振谱的分析,我们提出了一个可能的光致变色机理.