Kumar Prashant, Pérez-Escribano Manuel, van Raamsdonk Davita M E, Escudero Daniel
Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium.
J Phys Chem A. 2023 Aug 31;127(34):7241-7255. doi: 10.1021/acs.jpca.3c04205. Epub 2023 Aug 19.
In this contribution, we assess the computational machinery to calculate the phosphorescence properties of a large pool of heteroleptic [Ir(C^N)(N^N)] complexes (where N^N is an ancillary ligand and C^N is a cyclometalating ligand) including their phosphorescent rates and their emission spectra. Efficient computational protocols are next proposed. Specifically, different flavors of DFT functionals were benchmarked against DLPNO-CCSD(T) for the phosphorescence energies. The transition density matrix and decomposition analysis of the emitting triplet excited state enable us to categorize the studied complexes into different cases, from predominant triplet ligand-centered (LC) character to predominant charge-transfer (CT) character, either of metal-to-ligand charge transfer (MLCT), ligand-to-ligand charge transfer (LLCT), or a combination of the two. We have also calculated the vibronically resolved phosphorescent spectra and rates. Ir(III) complexes with predominant CT character are characterized by less vibronically resolved bands as compared to those with predominant LC character. Furthermore, some of the complexes are characterized by close-lying triplet excited states so that the calculation of their phosphorescence properties poses additional challenges. In these scenarios, it is necessary to perform geometry optimizations of higher-lying triplet excited states (i.e., T). We demonstrate that in the latter scenarios all of the close-lying triplet species must be considered to recover the shape of the experimental emission spectra. The global analysis of computed emission energies, shape of the computed emission spectra, computed rates, etc. enable us to unambiguously pinpoint for the first time the triplet states involved in the emission process and to provide a general classification of Ir(III) complexes with regard to their phosphorescence properties.
在本论文中，我们评估了用于计算大量杂配[Ir(C^N)(N^N)]配合物（其中N^N为辅助配体，C^N为环金属化配体）磷光性质的计算方法，包括它们的磷光速率和发射光谱。接下来提出了高效的计算方案。具体而言，针对磷光能量，将不同类型的DFT泛函与DLPNO-CCSD(T)进行了基准测试。发射三重激发态的跃迁密度矩阵和分解分析使我们能够将所研究的配合物分为不同情况，从以三重态配体为中心（LC）的主要特征到以电荷转移（CT）为主的特征，包括金属到配体的电荷转移（MLCT）、配体到配体的电荷转移（LLCT）或两者的组合。我们还计算了振转分辨的磷光光谱和速率。与具有主要LC特征的配合物相比，具有主要CT特征的Ir(III)配合物的振转分辨谱带较少。此外，一些配合物的特征是三重激发态能级相近，因此计算它们的磷光性质带来了额外的挑战。在这些情况下，有必要对较高能级的三重激发态（即T）进行几何优化。我们证明，在后者的情况下，必须考虑所有能级相近的三重态物种才能恢复实验发射光谱的形状。对计算得到的发射能量、计算得到的发射光谱形状、计算得到的速率等进行全局分析，使我们首次能够明确指出发射过程中涉及的三重态，并根据其磷光性质对Ir(III)配合物进行一般分类。
