基于[P_2W_(17)O_(61)]^(10-)构筑的一维双链稀土衍生物的结构、合成及表征

Structure,synthesis and characterization of a double-stranded polyoxometalate based on [P_2W_(17)O_(61)]^(10-) polyanion

饱和Dawson型[P_2W_(18)O_(62)]^(6-)(简称为[P_2W_(18)])多酸阴离子以其稳定的化学性质、良好的结晶性能成为多酸化学领域中的重要研究对象.本文以K_6[α-P_2W_(18)O_(62)]·xH_2O、Ce(NO_3)_3·6H_2O为基本原料,通过常规水溶液加热回流法,成功地合成了一例结构单元类似2∶17型Dawson-稀土双系列结构的一维双链化合物{[Na_2[N(CH_3)_4]_8[Ce(CH_3COO)(H_2O)]_2[Ce(H_2O)_7](P_2W_(17)O_(61))]_2·23H_2O}_n(1).结构分析表明,化合物1属于三斜晶系,P-1空间群,晶胞参数为:a=1.327 97(15)nm,b=1.376 71(15)nm,c=3.121 1(3)nm.该化合物以单缺位[P_2W_(17)O_(61)]^(10-)(简称为[P_2W_(17)])为基本构筑单元,中心原子Ce不仅与[P_2W_(17)]通过氧桥直接相连,而且通过醋酸根与另外一个Ce-[P_2W_(17)]单元相连,并最终形成新颖的一维双链结构.此外,我们还通过红外光谱、元素分析、热失重分析、紫外-可见吸收光谱分析等方法,对化合物1进行了较全面的表征.

The Dawson-type polyanion [P_2W_(18)O_(62)]^(6-)(denoted as [P_2W_(18)]) is an important precursor in polyoxometalate(POM) chemistry for its good chemical stability and excellent crystallization feature.Using K_6[α-P_2W_(18)O_(62)]·xH_2O and Ce(NO3)3·6 H2 O as starting materials.As a result,a novel double-stranded polyoxoanion { [Ce(CH_3COO)(H_2O)]_2[Ce(H_2O)_7](P_2W_(17)O_(61))}2·23H_2O(1) has been synthesized by conventional method.X-ray single crystal diffraction test reveals that compound 1 crystallizes in triclinic space group P-1 with cell parameter a = 1.327 97(15) nm,b =1.376 71(15) nm,c = 3.121 1(3) nm.Moreover,its unit structure is similar with the classic 2 ∶ 17 series POMs.Structural analysis demonstrated that Ce ions in compound 1 connect not only to the oxobridge of vacancy [P_2W_(17)O_(61)]^(10-)(denoted as [P_2W_(17)]) but also to another Ce-[P_2W_(17)] subunit through acetic linkers and finally forms a novel 1D double-stranded structure.In addition,1 was characterized by infrared(IR) spectroscopy,elemental analysis,thermogravimetric analysis and ultraviolet-visible(UV-Vis) spectroscopy carefully.