用ADF模拟[O,N]CpTiMeCl与MAO作用的一般机理

利用分子模拟技术探讨了钛配合物[O,N]CpTiMeCl（其中[O,N]为2－甲基－喹啉－8－氧基[C10H8NO])在助催化剂甲基铝氧烷（MAO）作用下催化烯烃聚合过程中形成活性中心的一般反应历程，量子力学计算表明，MAO大阴离子对负电荷的分散作用使形成金属阳离子的过程更加容易；乙烯单体与金属阳离子中心的配位反应是放热反应（－2.76kcal/mol），即乙烯能够稳金属阳离子，促进分离离子对的形成；AlMe3更易与MAO中氧原子作用形成加合物，而不是形成二甲基桥加合物；金属阳离子与MAO形成的氯桥加合物比形成与氧原子配位的加合物要稳定，计算结果表明，MAO中含一定量的AlMe3可以保护助催化酸性位，并对金属阳离子与MAO的加合物起着稳定化作用。     

Enhancement of Reverse Intersystem Crossing in Charge-Transfer Molecule through Internal Heavy Atom Effect

Thermally activated delayed fluorescence (TADF) is beneficial for improving the efficiency of organic light-emitting diodes (OLEDs) by providing pathways to convert non-emissive triplet excitons into singlet excitons. To ensure TADF is efficient, it is critical to enhance the reverse intersystem crossing (RISC) rate. To this end, most approaches propose thus far have focused on reducing the energy difference between S₁ and T₁ states. The present study explores how incorporating the internal heavy atom (IHA) effect can impact the RISC and device performance. By introducing a series of halogen atoms to charge-transfer molecules, TADF molecules exhibiting RISC over 7 × 10⁷ s⁻¹ are realized. These molecules are then applied to OLEDs, and the effect of incorporating these moieties is investigated. The results show that efficiency roll-off is still significant even with RISC-enhanced TADF emitters. Spectroscopic and theoretical results indicate that a fast RISC may not be the sole factor important for reducing efficiency roll-off and that the spin-flip cycles considering both T₁→S₁ and S₁→T₁ should be carefully taken into account to derive a complete picture of the IHA effect on efficiency roll-off behavior.