Investigation of Spin States of Excited Triplet States by a Newly Developed Double Group Theory

此前，Azumi研究了六核钼粉的磷光发射，并得出结论，磷光是由三个自旋亚能级组成的，这三个自旋亚能级源于自旋-轨道耦合的分裂。有时是晚些时候，格雷等人。艾尔报道了几个六核Re尘埃，并得出结论，该发射是由一些振动激发的三重态组成的。在这项工作中，完全没有考虑自旋-轨道耦合引起的分裂。另一方面，北村等人。艾尔从自旋-轨道耦合诱导的自旋亚能级的角度分析了类似的六核Re团簇。然而，与钼尘埃的情况不同，他们得出的结论是，发射是由四个自旋亚能级组成的，而不是三个。在这里，自旋子能级的性质还没有被澄清。由于所有这些钼和Re团簇都有相同的d电子数和相同的对称性，所以为什么发射机制不同是一个谜。为了使…在这一点上，我们又对不同反离子和不同卤素配体中的六核钼、铼原子团簇进行了新的研究，获得了许多有意义的信息。(2)PMMA聚合物基质中的发射与反离子完全无关，发射性质仅由中心尘埃离子决定，对寿命和发射峰值的温度依赖性分析表明，磷光是由自旋-轨道耦合产生的三个自旋子能级组成的。通过将观测到的温度扩展到3K这样的低温度，阐明了Jahn-lbller扭曲和由此产生的第二低自旋子能级的能量分裂。在工作的理论部分，我们得出结论，只基于过渡金属离子d电子的双群理论可以广泛和成功地应用于这类金属团簇。较少

Previously, Azumi investigated the phosphorescence emission from hexanuclear molybdenum duster, and concluded that the phosphorescence is composed of three spin sublevels that are originated from the splitting due to spin-orbit coupling. Sometimes later, Grey, et. al. reported several hexanuclear rhenium dusters and concluded that the emission is composed of a number of vibrationally excited triplet states. In this work, splitting due to spin-orbit coupling was not at all considered. On the other hand, Kitamura, et. al. analyzed similar hexanuclear rhenium clusters in terms of spin-orbit-coupling-induced spin sublevels. However, different from the Mo duster's case, they concluded that the emission is composed of four, not three, spin sublevels. Here, the nature of the spin sublevels has not been clarified. Since all of these molybdenum and rhenium clusters have identical number of d-electrons and have identical symmetry, why the emission mechanisms differ is puzzling.In order to clarif … More y this point, we have newly investigated series of hexanuclear molybdenum and rhenium clusters in various counter ions and also with variety of halogen ligands.From the series of experiments, a lot of meaningful information has been obtained. (1)all the molybdenum dusters and rhenium dusters exhibit almost identical temperature dependence on lifetimes and emission peak (2)The observations in PMMA polymer matrices indicate that the emission is completely independent of counter ions, and the emission properties are only determined by the central duster ions alone.Detailed analysis of the temperature dependence of lifetime and of emission peak clearly indicate that the phosphorescence is composed of three spin sublevels that are resulted from the spin-orbit coupling. Further by extending the observed temperatures to such a low temperature as 3 K, the Jahn-lbller distortion and the resulting energy splitting of the second lowest spin sublevels has been clarified.In the theoretical part of the work, we have concluded that the double group theory based on only d-electrons of transition metal ions can be widely and successfully applied to this sort of metal clusters. Less