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

此前，Azumi研究了六核钼簇的磷光发射，并得出结论，磷光是由三个自旋子能级组成的，它们是由于自旋轨道耦合引起的分裂。有时候，格雷，等。等人报道了几个六核双光子簇，并得出结论，发射是由许多振动激发的三重态组成的。在这项工作中，分裂由于自旋轨道耦合是在所有考虑。另一方面，Kitamura，et.等人分析了类似的六核双金属团簇的自旋轨道耦合诱导的自旋子能级。然而，与Mo duster的情况不同，他们得出的结论是，发射是由四个而不是三个自旋子级组成的。在这里，自旋子能级的性质还没有得到澄清。由于所有这些钼和钼原子团簇都具有相同的d-电子数和相同的对称性，为什么发射机制不同是令人困惑的。 关于我们 基于这一点，我们对六核钼簇和六核钼簇在不同反离子和不同卤素配体中的配合物进行了新的研究，从中获得了许多有意义的信息。（1）所有的钼粉和钼粉都表现出几乎相同的寿命和发射峰的温度依赖性（2）在PMMA聚合物基质中的观察表明发射完全不依赖于反离子，对磷光寿命和发射峰随温度变化的详细分析表明，磷光是由中心簇离子组成的由自旋轨道耦合产生的三个自旋子能级。进一步将实验温度推广到3 K，阐明了次低自旋子能级的Jahn-lbller畸变和由此产生的能量分裂，并在理论部分得出结论：仅以过渡金属离子d电子为基础的双群理论可以广泛而成功地应用于这类金属团簇。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