Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.
Inorg Chem. 2010 Oct 4;49(19):8977-85. doi: 10.1021/ic101257b.
Dinuclear platinum(II) complexes Pt(2)(μ-pz)(2)(bpym)(2) (1; pz = pyrazolate and bpym = 2,2'-bipyrimidine) and [Pt(2)(μ-pyt)(2)(ppy)(2)] (2; pyt = pyridine-2-thiolate and Hppy = 2-phenylpyridine) were theoretically investigated with density functional theory (DFT) to clarify the reasons why the phosphorescence of 1 is not observed in the acetonitrile (CH(3)CN) solution at room temperature (RT) but observed in the solid state at RT and why the phosphorescence of 2 is observed in both the CH(3)CN solution and the solid state at RT. The S(1) and T(1) states of 1 in the CH(3)CN solution are assigned as a metal-metal-to-ligand charge-transfer (MMLCT) excited state. Their geometries are C(2v) symmetrical, in which spin-orbit interaction between the S(1) and T(1) excited states is absent because the direct product of irreducible representations of the singly occupied molecular orbitals (SOMOs) of these excited states and the orbital angular momentum (l) operator involved in the Hamiltonian for spin-orbit interaction does not belong to the a(1) representation. As a result, the S(1) → T(1) intersystem crossing hardly occurs, leading to the absence of T(1) → S(0) phosphorescence in the CH(3)CN solution at RT. In the solid state, the geometry of the S(1) state does not reach the global minimum but stays in the C(1)-symmetrical local minimum. This S(1) excited state is assigned as a mixture of the ligand-centered π-π* excited state and the metal-to-ligand charge-transfer excited state. Spin-orbit interaction between the S(1) and T(1) excited states operates to induce the S(1) → T(1) intersystem crossing because the direct product of the irreducible representations of the SOMOs of these excited states and the l operator belongs to the "a" representation. As a result, T(1) → S(0) phosphorescence occurs in the solid state. In 2, the S(1) and T(1) excited states are assigned as the MMLCT excited state. Their geometries are C(2)-symmetrical in both the CH(3)CN solution and the solid state, in which spin-orbit interaction between the S(1) and T(1) states operates to induce the S(1) → T(1) intersystem crossing because the direct product of the irreducible representations of the SOMOs and the l operator belongs to the "a" representation. Thus, T(1) → S(0) phosphorescence occurs in both the CH(3)CN solution and the solid state at RT, unlike 1.
双核铂(II)配合物Pt(2)(μ-pz)(2)(bpym)(2)（1；pz=吡唑酸盐，bpym=2,2'-联吡啶）和[Pt(2)(μ-pyt)(2)(ppy)(2)]（2；pyt=吡啶-2-硫醇盐，Hppy=2-苯基吡啶）用密度泛函理论（DFT）进行了理论研究，以阐明为什么 1 的磷光在室温（RT）下的乙腈（CH(3)CN）溶液中不被观察到，但在 RT 下的固态中被观察到，以及为什么 2 的磷光在 RT 下的 CH(3)CN 溶液和固态中都被观察到。1 在 CH(3)CN 溶液中的 S(1)和 T(1)态被指定为金属-金属到配体电荷转移（MMLCT）激发态。它们的几何形状为 C(2v)对称，其中 S(1)和 T(1)激发态之间的自旋轨道相互作用不存在，因为这些激发态的单占据分子轨道（SOMOs）的不可约表示的直接乘积和涉及自旋轨道相互作用的哈密顿量的轨道角动量（l）算子不属于 a(1)表示。结果，S(1)→T(1)系间交叉几乎不发生，导致在 RT 下的 CH(3)CN 溶液中没有 T(1)→S(0)磷光。在固态中，S(1)态的几何形状未达到全局最小值，而是停留在 C(1)对称的局部最小值。这个 S(1)激发态被指定为配体中心的π-π*激发态和金属-配体电荷转移激发态的混合物。S(1)和 T(1)激发态之间的自旋轨道相互作用起作用以诱导 S(1)→T(1)系间交叉，因为这些激发态的 SOMOs 的不可约表示的直接乘积和 l 算子属于“a”表示。结果，T(1)→S(0)磷光在固态中发生。在 2 中，S(1)和 T(1)激发态被指定为 MMLCT 激发态。它们在 CH(3)CN 溶液和固态中的几何形状均为 C(2)-对称，其中 S(1)和 T(1)态之间的自旋轨道相互作用起作用以诱导 S(1)→T(1)系间交叉，因为 SOMOs 和 l 算子的不可约表示的直接乘积属于“a”表示。因此，T(1)→S(0)磷光在 RT 下的 CH(3)CN 溶液和固态中都发生，这与 1 不同。
