中文摘要：

采用DFT／TDDFT方法研究了二米基硼B（Mes）2基团修饰的一类Ir（ppy）2（acac）配合物1～3的光物理性质．计算了电子结构，吸收和发射光谱以及自旋轨道耦合矩阵〈T1σ｜HSOC｜Sn〉和辐射跃迁速率（杆），探讨了取代基位置不同对磷光辐射和非辐射跃迁性质的影响．研究结果表明：向ppy配体的吡啶环引入B（Mes）2基团，能够加强金属铱（Ir）与配体乙酰丙酮（acac）的相互作用，减小单一三重态能级差△E（S1-T1），提高系间窜跃速率和磷光辐射跃迁速率．向PPY配体的苯环引入B（Mes）2基团则增大了S0与T1的结构变形和自旋轨道耦合矩阵〈S0｜HSOC}T1〉），使非辐射跃迁速率增加．B（Mes），基团位置异构，导致金属d轨道分裂方式不同，其在三个方向的自旋轨道耦合作用不同，辐射跃迁和非辐射跃迁都随之改变．从理论上解释了通过对PPY配体的吡啶环修饰可获得高磷光量子产率的原因．

英文摘要：

The phosphorescent photophysical properties for three lr（Ⅲ） complexes 1~3 containing dimesitylboryl moiety were investigated by DFT. The electronic structure of the ground and excited state, absorption and emission spectra, the spin-orbital coupling matrix 〈T1σ｜HSOC｜Sn〉, the radiative and non-radiative transition process for complexes 1~3 were cal- culated by DFT/TD-DFT approach. The effect of dimesitylboryl substitution at different site of Ir（Ⅲ） complex with phe- nylpyridine and acetylacetone ligand on the phosphorescent radiative and non-radiative process was discussed. The results reveal that the introduction of B（Mes）2 group to the pyridine ring of the phenylpyridine （ppy） ligand can strengthen the inter- actions between the metal and the acetylacetone （acac） ligand, reduce the structure relaxation of the molecule from the ground state to the excited triplet state, and maintain the structures of octahedral field, which is conducive to restricted non-radiative transition. Moreover the singlet-triplet energy splitting △E（S1-T1） is decreased, the intersystem crossing rate and radiative transition rate are increased. In addition, compared with the substitution at the pyridinyl in complex 1, modifying phenyl group with B（Mes）2 group in complex 2 and 3 could induce larger structural changes from So to T1 state and enhance the 〈S0｜HSOC｜T1） value, the spin orbit coupling matrix element between So and T1 state of 2 and 3 are greater than that of 1, which will induce a larger non-radiative transition rate for 2 and 3, The variety of substitution position of B（Mes）2 group leads to different d-splitting, different spin-orbital coupling effect in the x, y or z direction, induces the changes of zero field splitting energy and the inequality of radiative transition rates in the three substates （namely, krx, kry, and krz）, and the largest radiative rates of 1~3 are all located in z substates with values of 2.32× 10^5, 1.20× 10^5, and 5.50× 10^5 s^-1, respectively