Cyclometalation Geometry of the Bridging Ligand as a Tuning Tool for Photophysics of Dinuclear Ir(III) Complexes
Cyclometalation Geometry of the Bridging Ligand as a Tuning Tool for Photophysics of Dinuclear Ir(III) Complexes
复制标题
DOI：
10.1021/acs.jpcc.1c05037
复制
发表时间：
2021-09
期刊：
影响因子：
--
通讯作者：
M. Shafikov;A. Zaytsev;V. N. Kozhevnikov
中科院分区：
文献类型：
--
作者：
M. Shafikov;A. Zaytsev;V. N. Kozhevnikov
桥联配体在双核金属配合物的发光设计中起着至关重要的作用。双环化配体产生了一个大家族的高效发射体。在这里，我们研究了切换的环化功能的桥接（发色团）配体的双核Ir（III）配合物的物理性质的影响。新的双核Ir（III）配合物（Ir-1）由一个桥连发色配体和两个末端环化的苯基衍生物组成，中心为二氮配位的噻唑并[5，4-d]噻唑衍生物，在二氯甲烷溶液中室温下显示出良好的红色磷光（ΦPL= 12%，τ = 1.5 μs，λ = 635 nm）.这是几倍更有效的性能相比，较早报道的双核Ir（III）配合物IrIr，与桥接配体包括终端氮配位的吡啶衍生物和中心环化噻吩并[3，2-B]噻吩衍生物，在相同的条件下（ΦPL= 3.5%，τ = 2.9 μs，和λ = 714 nm）。桥连配体的这种“C/N交换”导致Ir-1的磷光发生蓝移，提高了磷光效率。这种效应的起因是T1态交换作用的显著降低，从而使ΔE（S1- T1）能隙变小。根据密度泛函理论的计算，这是由于桥连配体中最高占据分子轨道的分布更均匀（更宽），以及金属中心和卤素原子在状态S1和T1形成中的参与增加。与Ir-1类似，Ir-2中桥连配体上的取代基模式的调制提供了磷光速率的选择性调谐，而磷光的其他性质在相同条件下保持相似（ΦPL= 15%，τ = 3.1 μs，λ = 632 nm）。
Bridging ligands play a crucial role in design of luminescent dinuclear metal complexes. Bis-cyclometalating ligands gave rise to a large family of highly efficient emitters. Herein, we investigate the effect of switching the cyclometalating function of the bridging (chromophoric) ligand on photophysical properties of dinuclear Ir(III) complexes. The new dinuclear Ir(III) complex (Ir-1), comprising a bridging chromophoric ligand with two terminal cyclometalating phenyl derivatives, conjugated to the central twice nitrogen-coordinating thiazolo[5,4-d]thiazole derivative, displays red phosphorescence of decent efficiency in CH2Cl2solution at room temperature (ΦPL= 12%, τ = 1.5 μs, and λ = 635 nm). This is several times more efficient compared to the properties of the earlier reported dinuclear Ir(III) complexIrIr, with a bridging ligand comprising terminal nitrogen-coordinating pyridine derivatives and a central cyclometalating thieno[3,2-b]thiophene derivative, under the same conditions (ΦPL= 3.5%, τ = 2.9 μs, and λ = 714 nm). This “C/N swap” within the bridging ligand caused blue-shifted and improved efficiency of phosphorescence ofIr-1. The origin of this effect is the significantly reduced exchange interaction in state T1and, consequently, smaller ΔE(S1– T1) energy gap. According to the density functional theory calculations, this comes from the more even (wider) distribution of the highest occupied molecular orbital within the bridging ligand and increased participation of the metal centers and halide atoms in the formation of states S1and T1. Modulation of the substituent pattern on the bridging ligand in complexIr-2, analogous toIr-1, afforded selective tuning of the phosphorescence rate, whereas other properties of phosphorescence remained similar under the same conditions (ΦPL= 15%, τ = 3.1 μs, and λ = 632 nm).