Li Guijie, Wolfe Alicia, Brooks Jason, Zhu Zhi-Qiang, Li Jian
Department of Materials Science and Engineering, Arizona State University , Tempe, Arizona 85284, United States.
College of Chemical Engineering, Zhejiang University of Technology , Hangzhou, Zhejiang 310014, China.
Inorg Chem. 2017 Jul 17;56(14):8244-8256. doi: 10.1021/acs.inorgchem.7b00961. Epub 2017 Jun 26.
The design, synthesis, and characterization of a series of tetradentate cyclometalated Pt(II) complexes are reported. The platinum complexes have the general structure Pt(ppz-O-CbPy-R), where a tetradentate cyclometalating ligand is consisting of ppz (3,5-dimethyl-1-phenyl-pyrazole), CbPy (carbazolylpyridine) components, and an oxygen bridging group. Variations of the R group on the pyridyl ring with various electron withdrawing and donating substituents are shown to have profound effects on the photophysical properties of Pt complexes. Electrochemical analysis indicates that reduction process occurs mainly on the electron-accepting pyridyl group, and the irreversible oxidation process is primarily localized on the metal-phenyl portions. The studies of their photophysical properties indicate that the lowest excited state of the platinum complexes is a ligand-centered π-π* state with minor to significant MLCT/MLCT character and are strongly dependent on the nature of the electron-accepting pyridyl moiety. A systematic study of the substituent effects on the pyridyl ring demonstrates that the T state properties can be tuned by altering the functionality and positions of substituents. Importantly, it is revealed that how the emission spectra of the Pt(II) complexes can be significantly narrowed and why it can be achieved by incorporating an electron-donating group on the 4-position of the pyridyl ring. Most of the Pt(II) complexes reported here are highly emissive at room temperature in dichloromethane solutions (Φ = 1.1-95%) and in doped PMMA films (Φ = 29-88%) with luminescent lifetimes in the microsecond range (τ = 0.6-13.5 μs in solution and 0.9-11.3 μs in thin film respectively) and λ = 442-568 nm and 440-544 nm in solution and thin film, respectively. Moreover, these complexes are neutral and thermally stable for sublimation, indicating that they can be useful for display and solid-state lighting applications.
报道了一系列四齿环金属化铂（II）配合物的设计、合成及表征。这些铂配合物具有通式Pt(ppz-O-CbPy-R)，其中四齿环金属化配体由ppz（3,5-二甲基-1-苯基吡唑）、CbPy（咔唑基吡啶）组分以及一个氧桥连基团组成。吡啶环上带有各种吸电子和供电子取代基的R基团变化对铂配合物的光物理性质有深远影响。电化学分析表明，还原过程主要发生在吸电子的吡啶基团上，不可逆氧化过程主要集中在金属-苯基部分。对其光物理性质的研究表明，铂配合物的最低激发态是以配体为中心的π-π*态，具有轻微到显著的MLCT/MLCT特征，并且强烈依赖于吸电子吡啶部分的性质。对吡啶环上取代基效应的系统研究表明，可以通过改变取代基的官能团和位置来调节T态性质。重要的是，揭示了如何显著窄化铂（II）配合物的发射光谱以及为何通过在吡啶环的4-位引入供电子基团能够实现这一点。这里报道的大多数铂（II）配合物在室温下于二氯甲烷溶液（Φ = 1.1 - 95%）和掺杂的PMMA薄膜（Φ = 29 - 88%）中具有高发射性，发光寿命在微秒范围内（溶液中τ = 0.6 - 13.5 μs，薄膜中τ = 0.9 - 11.3 μs），溶液和薄膜中的发射波长分别为λ = 442 - 568 nm和440 - 544 nm。此外，这些配合物呈中性且热稳定性良好，可用于升华，表明它们可用于显示和固态照明应用。
