Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
J Am Chem Soc. 2010 Dec 15;132(49):17537-49. doi: 10.1021/ja106902s. Epub 2010 Nov 22.
Multiconfigurational, intermediate valent ground states are established in several methyl-substituted bipyridine complexes of bis(pentamethylcyclopentadienyl)ytterbium, Cp2Yb (Me(x)-bipy). In contrast to Cp2Yb(bipy) and other substituted-bipy complexes, the nature of both the ground state and the first excited state are altered by changing the position of the methyl or dimethyl substitutions on the bipyridine rings. In particular, certain substitutions result in multiconfigurational, intermediate valent open-shell singlet states in both the ground state and the first excited state. These conclusions are reached after consideration of single-crystal X-ray diffraction (XRD), the temperature dependence of X-ray absorption near-edge structure (XANES), extended X-ray absorption fine-structure (EXAFS), and magnetic susceptibility data, and are supported by CASSCF-MP2 calculations. These results place the various Cp2*Yb(bipy) complexes in a new tautomeric class, that is, intermediate-valence tautomers.
多组态、中间价基态在双（五甲基环戊二烯基）镱的几种甲基取代联吡啶配合物 Cp2Yb（Me(x）-bipy）中建立。与 Cp2Yb（bipy）和其他取代联吡啶配合物不同，通过改变联吡啶环上甲基或二甲基取代的位置，基态和第一激发态的性质都发生了变化。特别是某些取代导致基态和第一激发态中都出现多组态、中间价开壳单重态。这些结论是在考虑单晶 X 射线衍射（XRD）、X 射线吸收近边结构（XANES）、扩展 X 射线吸收精细结构（EXAFS）和磁化率数据后得出的，并得到 CASSCF-MP2 计算的支持。这些结果将各种 Cp2*Yb（bipy）配合物置于一个新的互变异构体类别中，即中间价互变异构体。
