Shimotani Hidekazu, Ito Takayoshi, Iwasa Yoshihiro, Taninaka Atsushi, Shinohara Hisanori, Nishibori Eiji, Takata Masaki, Sakata Makoto
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
J Am Chem Soc. 2004 Jan 14;126(1):364-9. doi: 10.1021/ja038208i.
The configuration of La ions of La(2)@C(80) in the [80]fullerene cage was investigated by use of quantum chemical calculations. We found that the D(3)(d)() configuration is the global minimum in total energy, being more stable by 1.9 kcal/mol than the D(2)(h)() configuration, which has been considered to be the most stable. The potential energy surface calculation clarified that La ions travel between 10 equivalent D(3)(d)() positions through D(2)(h)() positions and consequently form pentagonal dodecahedral trajectory, which is in good agreement with the previous synchrotron radiation structural study. The experimental and theoretical investigation of the Raman spectrum revealed that the symmetry of molecular vibration is dramatically reduced simply by encapsulation of two La ions, and resulting vibrational modes were successfully assigned. The Raman peak at 163 cm(-)(1) was interpreted as the in-phase synchronously coupled mode of the [80]fullerene cage elongation and the La-La stretching, rather than a conventional and naive assignment as a metal-to-cage vibration mode.
通过量子化学计算研究了La(2)@C(80)中La离子在[80]富勒烯笼中的构型。我们发现D(3)(d)构型是总能量的全局最小值，比被认为最稳定的D(2)(h)构型能量低1.9 kcal/mol。势能面计算表明，La离子通过D(2)(h)位置在10个等效的D(3)(d)位置之间移动，从而形成五角十二面体轨迹，这与先前的同步辐射结构研究结果高度吻合。拉曼光谱的实验和理论研究表明，仅通过包裹两个La离子，分子振动的对称性就会显著降低，并且成功地对产生的振动模式进行了归属。163 cm(-)(1)处的拉曼峰被解释为[80]富勒烯笼伸长与La-La拉伸的同相同步耦合模式，而不是传统的、简单的作为金属-笼振动模式的归属。
