高效膦基锇配合物磷光材料的结构和光谱性质

采用B3LYP和UB3LYP方法分别优化了一系列(N^N)2Os(P^P)P^P=1,2-双(膦基)-甲基,N^N=5-(苯并咪唑-2-基)-3-三氟甲基吡啶(1);ibfpH=5-(1-异丙基-苯并咪唑-2-基)-3-三氟甲基吡啶(2);fppzH=5-(吡啶-2-基)-3-三氟甲基吡啶(3);tfpH=5-(噻唑-2-基)-3-三氟甲基吡啶(4);btfpH=5-(苯基噻唑-2-基)-3-三氟甲基吡啶(5)]配合物的基态和激发态结构.计算得到的Os-P(1),Os-N(1)和Os-N(2)基态键长和相应实验值符合较好.相对于基态,激发态几何结构变化较小,与实验上观察到的斯托克斯频移相一致.配合物1-5的最高占据分子轨道主要由Os的d轨道和N^N配体的π轨道构成,而它们的最低空轨道主要由N^N配体的π反键轨道占据,前线分子轨道能量受N^N配体影响较大.在TD-DFT计算水平下结合PCM溶剂模型,得到配合物1-5的最低能吸收和发射分别在415,416,465,458,481nm和541,538,569,629,655nm.这些跃迁均来自于HOMO→LUMO的激发,具有MLCT/ILCT混合跃迁性质,并且它们的高能吸收也具有相似的跃迁特征.发射波长的巨大差异显示出通过调节N^N配体的π电子捐赠能力可以实现对此类配合物发光颜色的调节.

The structures and spectroscopic properties of highly efficient phosphorescent osmium complexes with phosphino group

The geometries and electronic structures of a series of Os(Ⅱ) complexes (N^N)2Os(P^P)P^P=1,2-bis (phosphino)-methyl,N ^ N =5-(benzimidazol-2-yl)-3-trifluoromethyl pyrazole (1),ibfpH =5-(1-isopropyl-benzimidazol-2-yl)-3-trifluoromethylpyrazole (2),fppzH =5-(pyridine-2-yl)-3-tri-fluoromethylpyrazole (3),tfpH =5-(thiazol 2-yl)-3-trifluoro-methylp-yrazole (4),btfpH =5-(ben-zothiazol-2-yl)-3-trifluoromethylpyrazole(5)] were optimized by the B3LYP and UB3LYP method,respectively.The calculated bond lengths of Os P(1),Os-N(1),and Os-N(2) in the ground state agree well with the corresponding experimental results.There were slight structural differences between ground and excited states,and this was in agreement with the small Stokes shift observed in the experiments.The highest occupied molecular orbitals were dominantly localized on the d orbital of Os and π orbital of N^N ligand,while the lowest unoccupied molecular orbitals were mainly composed of π* orbital of N^N ligand,the frontier molecular orbital energy is affected by N^N ligand.At the TDDFT level with the PCM model,1-5 give rise to lowest-lying absorptions at 415,416,465,458 and 481 nm and phosphorescent emissions at 541,538,569,629 and 655 nm,respectively.These transition arises from HOMO→LUMO excitation with MLCT/ILCT characters,and the high energy absorption also have similar transition properties.The calculation results show that the phosphorescent color can be changed by altering the π electron-withdrawing ability of the N^N ligand.