Shafikov Marsel Z, Zaytsev Andrey V, Kozhevnikov Valery N
Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstrasse 31, Regensburg D-93053, Germany.
Department for Technology of Organic Synthesis, Institute of Chemical Technology, Ural Federal University, Mira 19, Ekaterinburg 620002, Russia.
Inorg Chem. 2021 Jan 18;60(2):642-650. doi: 10.1021/acs.inorgchem.0c02469. Epub 2021 Jan 6.
The spin-forbidden nature of phosphorescence in Ir(III) complexes is relaxed by the metal-induced effect of spin-orbit coupling (SOC). A further increase of the phosphorescence rate could potentially be achieved by introducing additional centers capable of further enhancing the SOC effect, such as metal-coordinated halides. Herein, we present a dinuclear Ir(III) complex that contains two Ir(III)-iodide moieties. The complex shows intense phosphorescence with a quantum yield of Φ(300 K) = 90% and a submicrosecond decay time of only τ(300 K) = 0.34 μs, as measured under ambient temperature for the degassed toluene solution. These values correspond to a top value T → S phosphorescence rate of = 2.65 × 10 s. Investigations at cryogenic temperatures allowed us to determine the zero-field splitting (ZFS) of the emitting state T ZFS(III-I) = 170 cm and unusually short individual decay times of T substates: τ(I) = 6.4 μs, τ(II) = 7.6 μs, and τ(III) = 0.05 μs. This indicates a strong SOC of state T with singlet states. Theoretical investigations suggest that the SOC of state T with singlets is also contributed by halides. Strongly contributing to the higher occupied molecular orbitals of the complex (e.g., HOMO, HOMO - 1, and so forth), iodides work as important SOC centers that operate in tandem with metals. The examples of and of earlier reported analogous complex reveal that the metal-coordinated halides can enhance the SOC of state T with singlets and, consequently, the phosphorescence rate. A comparative study of and shows that the share of halides in total contribution (halides plus metals) to the SOC of state T with singlets increases strongly upon exchange of chlorides for iodides. The exchange also led to the decrease in values of ZFS of the T state from ZFS(III-I) = 205 cm for to T ZFS(III-I) = 170 cm for . This results in a more efficient thermal population of the fastest emitting T substate III, thus further enhancing the room-temperature phosphorescence rate.
铱（III）配合物中磷光的自旋禁阻特性通过自旋轨道耦合（SOC）的金属诱导效应得以缓解。通过引入能够进一步增强SOC效应的额外中心，如金属配位卤化物，有可能进一步提高磷光速率。在此，我们展示了一种双核铱（III）配合物，它包含两个铱（III）-碘化物部分。在室温下对脱气甲苯溶液进行测量时，该配合物显示出强烈的磷光，量子产率为Φ(300 K) = 90%，衰变时间仅为τ(300 K) = 0.34 μs的亚微秒级。这些值对应于T → S磷光速率的最高值 = 2.65 × 10 s。在低温下的研究使我们能够确定发射态T的零场分裂（ZFS）为ZFS(III-I) = 170 cm以及T子态异常短的单个衰变时间：τ(I) = 6.4 μs，τ(II) = 7.6 μs，和τ(III) = 0.05 μs。这表明T态与单重态之间存在强烈的SOC。理论研究表明，T态与单重态之间的SOC也由卤化物贡献。碘化物对配合物的较高占据分子轨道（如HOMO、HOMO - 1等）有很大贡献，作为重要的SOC中心与金属协同作用。 和早期报道的类似配合物 的例子表明，金属配位卤化物可以增强T态与单重态之间的SOC，从而提高磷光速率。对 和 的比较研究表明，在T态与单重态之间的SOC的总贡献（卤化物加金属）中，卤化物的份额在将氯化物换成碘化物后大幅增加。这种交换还导致T态的ZFS值从 的ZFS(III-I) = 205 cm降至 的T ZFS(III-I) = 170 cm。这导致发射最快的T子态III的热激发更有效，从而进一步提高室温磷光速率。
