三例同构稀土/钨氧簇化合物二维红外相关光谱研究  

Two-Dimensional Infrared Spectroscopic Study of Three Isomorphic Rare Earth/Polyoxotungstates

作　　者：潘英民 陈义平 石林 龚智慧 毕文超 孙燕琼 PAN Ying-min;CHEN Yi-ping;SHI Lin;GONG Zhi-hui;BI Wen-chao;SUN Yan-qiong(Department of Chemistry,Fuzhou University,Fuzhou 350108,China;State Key Laboratory of Fujian Institute of Material Structure,Chinese Academy of Sciences,Fuzhou 350002,China)

机构地区：[1]福州大学化学学院,福建福州350108 [2]中国科学院福建物质结构研究所国家重点实验室,福建福州350002

出　　处：《光谱学与光谱分析》2020年第7期2104-2109,共6页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(21473030,21371033);中国科学院结构化学国家重点实验室开放基金项目;福建省大学生创新创业项目(201810386052)资助。

摘　　要：多酸化合物(POMs)是一类重要的多金属氧簇,由过渡金属在其高氧化态(V^Ⅴ, Nb^Ⅴ, Ta^Ⅴ,Mo^Ⅵ,Mo^Ⅴ及W^Ⅵ)与氧桥联的簇阴离子组成。在前人研究基础(H2en)2{SiW11O39Sm(H2O)2}·(H3O)·6H2O之上,改变稀土盐,成功合成了与其同构的三例晶体(H2en)2{SiW11O39Ln(H2O)2}·(H3O)·6H2O[Ln=Ce(1), Pr(2), Nd(3)], X-射线单晶衍射实验测得四者属于三斜晶系,P1空间群,晶胞参数一致,表明它们晶体结构相同;X-射线粉末衍射实验显示四者峰位相同,表明物相一致。此类同构的晶体,由于簇阴离子相同,仅取代的稀土离子不同,在许多表征方式上,显示出类似的现象,例如一维红外光谱吸收曲线相似,在1 039, 949, 889和787 cm^-1均出现了归属于Keggin簇阴离子骨架的振动吸收,在3 600~3 300和1 600~1 630 cm^-1附近均出现νas(O—H)及δ(O—H)的吸收峰,在3 277, 2 927和2 855 cm^-1内均出现了乙二胺配体N—H和C—H伸缩振动峰。但是磁微扰下的二维红外相关光谱,磁性粒子对磁场响应很敏感,热微扰下的二维红外相关光谱,易于捕捉氢键振动模式的细微变化。因此,二维红外光谱可以用于精细测定分子结构,并且此类同构钨氧簇合物的二维红外光谱对比分析还未见报道。磁微扰下的二维红外相关光谱,化合物1在468, 560和810 cm^-1出现响应峰,分别归属于νas(Ce—O),骨架ν(W—O),νas(W—Ob)。化合物2在450,464和475 cm^-1出现νas(Pr—O), 570和675 cm^-1处响应峰归属于骨架ν(W—O)。化合物3在452, 468和472 cm^-1处响应峰归属于νas(Nd—O), 518, 533, 545, 565和695 cm^-1响应峰为骨架ν(W—O)。化合物1, 2, 3归属于骨架ν(W—O)的响应峰数目增多,这是由于磁微扰下的二维红外光谱, Ce^3+, Pr^3+, Nd^3+价电子组态分别为4f^1, 4f^2, 4f^3,价电子数增加,磁性粒子Ln^3+对邻近W—O键影响变大。热微扰下的二维红外相关光谱,化合物1, 2, 3均在400 cm^-1左右出现了νas(Ln—O)响应峰, 810, 860和940 Polyoxometalates(POMs)are an important class of metal-oxygen clusters,which are composed of cluster anions bridged by pre-transition metals(V^Ⅴ,Nb^Ⅴ,Ta^Ⅴ,MoⅥ,Mo^Ⅴand W^Ⅵ)and oxygen.On the basis of previous studies(H2en)2{SiW11O39Sm(H2O)2}·(H3O)·6 H2O,we changed rare earth salts and successfully synthesized three isomorphic crystals(H2en)2{SiW11O39Ln(H2O)2}·(H3O)·6 H2O[Ln=Ce(1),Pr(2),Nd(3)],X-ray single crystal diffraction experiment measured that the four belong to the triclinic system,the P1 space group,and the unit cell parameters are consistent,indicating that they have the same crystal structure.XRD experiments show that they have the same peaks,indicating that the substances are identical.Due to the same cluster anions and only the substituted rare earth ions are different,these isomorphic crystals exhibit similar phenomena in many characterization methods,for example the similar absorption curves in 1 D infrared spectroscopy:the vibrational absorption of anion skeleton belonging to Keggin cluster appears at 1039,949,889 and 787 cm^-1,and the absorption peaks ofνas(O—H)andδ(O—H)occur in the vicinity of 3600~3300 and 1600~1630 cm^-1.The stretching vibration peaks of N—H and C—H ligands of ethylenediamine were observed in 3277,2927 and 2855 cm^-1.However,the two-dimensional infrared correlation spectra under magnetic perturbation are sensitive to the magnetic field response.The two-dimensional infrared correlation spectra under thermal perturbation are easy to capture the subtle changes of hydrogen bond vibration modes.Therefore,two-dimensional infrared spectroscopy can be used for fine determination of molecular structure,and the comparative analysis of two-dimensional infrared spectroscopy of such isomorphic polyoxotungstate has not been reported.Two-dimensional infrared correlation spectra under magnetic perturbation show that compound 1 has response peaks at 468,560 and 810 cm^-1,which belong toνas(Ln—O),skeletonν(W—O)andνas(W—Ob),respectively.Compound 2 exhibits as(Ln—

关 键 词：钨氧簇化合物 KEGGIN结构 二维红外相关光谱 

分 类 号：O657.3[理学—分析化学]