4,4′-联吡啶多钼酸盐的合成、结构与变色性质

通过水热合成法,合成了4,4′-联吡啶多钼酸盐((4,4′-bipyridine)Mo7O22·H2O)单晶超分子化合物.通过元素分析、热重-差热分析(TG-DTA)、粉末X射线衍射(XRD)、单晶X射线衍射、傅里叶变换红外(FTIR)光谱、紫外-可见漫反射光谱(UV-VisDRS)和电子自旋共振(ESR)技术对其组成、热稳定性、结构、光谱和电子特性进行了表征.实验结果表明:该超分子化合物的分子式为C10H12Mo7N2O23,在空气中320℃以下不分解.属于单斜晶系(空间群为P2/n),晶胞参数为a=1.22561(19)nm,b=0.55222(9)nm,c=1.8385(3)nm,β=103.221(2)°,V=1.2113(3)nm3,Z=2和Dc=3.289g·cm-3.基于F2的最终统计:GOF=0.982,R1=0.0228和wR2=0.0557(I2σ(I)).该单晶超分子化合物由质子化的4,4′-联吡啶阳离子和多金属钼酸盐阴离子Mo7O22]2-及结晶水组成.它们通过氢键、静电引力和分子间作用力结合在一起的,并构成二维网络结构.样品在光照或加热条件下具有光致变色和热致变色性质.XRD和FTIR证明,变色前后,样品的结构除轻微的畸变外几乎没有变化;而ESR结果表明,光致变色与热致变色的机理可能存在差别.该光致和热致变色的超分子化合物能够为变色机理研究提供参考模型,并在传感器和光敏材料等领域具有潜在应用.

Synthesis,Structure and Chromic Properties of 4,4'-Bipyridine Polyoxomolybdate

We synthesized a 4,4'-bipyridine polyoxomolybdate ((4,4'-bipyridine)Mo7O22·H2O) single crystal supramolecular compound by a hydrothermal method and characterized its composition, thermostability, structure, spectra and electron properties by elemental analysis, thermal gravimetric and differential thermal analysis (TG-DTA), powder X-ray diffraction (XRD), single crystal X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), and electron spin resonance (ESR). Experimental results show that the molecular formula of the supramolecular compound is C10H12Mo7N2O23 and it does not decompose below 320 ℃ in air. It belongs to the monoclinic system(space group P2/n) with a=1.22561(19) nm, b=0.55222(9) nm, c=1.8385(3) nm, β=103.221(2)°, V=1.2113(3) nm3, Z=2 and Dc=3.289 g·cm-3. The final statistics based on F2 are GOF=0.982, R1=0.0228 and wR2=0.0557 for I >2σ(I). The single crystal supramolecular compound consists of protonated 4,4'-bipyridine cations and polyoxomolybdate Mo7O22]2- anions as well as lattice water. They form a two dimensional (2D) network through hydrogen bonds, electrostatic attraction, and intermolecular forces. The samples show photochromism under UV irradiation and thermochromism under annealing conditions. XRD and FTIR verify that before and after the color changes, the crystal structure of the samples is almost unchanged except for distortion. ESR spectra indicate that a difference exists between the thermochromic and photochromic mechanisms. This supramolecular compound with thermochromic and photochromic behaviors can serve as a reference model for a chromic mechanism and may have potential application in fields such as sensors and photosensitive materials.