Cai Wenting, Morales-Martínez Roser, Zhang Xingxing, Najera Daniel, Romero Elkin L, Metta-Magaña Alejandro, Rodríguez-Fortea Antonio, Fortier Skye, Chen Ning, Poblet Josep M, Echegoyen Luis
Department of Chemistry , University of Texas at El Paso , 500 W University Avenue , El Paso , Texas 79968 , USA . Email:
Departament de Química Física i Inorgànica , Universitat Rovira i Virgili , C/Marcel⋅lí Domingo 1 , 43007 Tarragona , Spain.
Chem Sci. 2017 Aug 1;8(8):5282-5290. doi: 10.1039/c7sc01711a. Epub 2017 May 22.
Charge transfer is a general phenomenon observed for all endohedral mono-metallofullerenes. Since the detection of the first endohedral metallofullerene (EMF), La@C, in 1991, it has always been observed that the oxidation state of a given encapsulated metal is always the same, regardless of the cage size. No crystallographic data exist for any early actinide endohedrals and little is known about the oxidation states for the few compounds that have been reported. Here we report the X-ray structures of three uranium metallofullerenes, U@-C, U@(5)-C and U@(9)-C, and provide theoretical evidence for cage isomer dependent charge transfer states for U. Results from DFT calculations show that U@-C and U@(5)-C have tetravalent electronic configurations corresponding to U@-C and U@(5)-C. Surprisingly, the isomeric U@(9)-C has a trivalent electronic configuration corresponding to U@(9)-C. These are the first X-ray crystallographic structures of uranium EMFs and this is first observation of metal oxidation state dependence on carbon cage isomerism for mono-EMFs.
电荷转移是在所有内嵌单金属富勒烯中观察到的普遍现象。自1991年首次检测到内嵌金属富勒烯（EMF）La@C以来，人们一直观察到，无论笼尺寸如何，给定封装金属的氧化态始终相同。目前尚无任何早期锕系元素内嵌物的晶体学数据，对于已报道的少数化合物的氧化态也知之甚少。在此，我们报告了三种铀金属富勒烯U@-C、U@(5)-C和U@(9)-C的X射线结构，并为U的笼异构体依赖电荷转移态提供了理论证据。密度泛函理论（DFT）计算结果表明，U@-C和U@(5)-C具有对应于U@-C和U@(5)-C的四价电子构型。令人惊讶的是，异构体U@(9)-C具有对应于U@(9)-C的三价电子构型。这些是铀EMF的首批X射线晶体学结构，也是首次观察到单EMF的金属氧化态依赖于碳笼异构现象。
