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首页> 外文期刊>RSC Advances >Charge-transfer excited states in phosphorescent organo-transition metal compounds: a difficult case for time dependent density functional theory?
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Charge-transfer excited states in phosphorescent organo-transition metal compounds: a difficult case for time dependent density functional theory?

机译：磷光有机化金属化合物中的电荷转移激发状态：时间依赖性密度函数理论的难度案例？

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摘要

Light emitting organo-transition metal complexes have found widespread use in the past. The computational modelling of such compounds is often based on time-dependent density functional theory (TDDFT), which enjoys popularity due to its numerical efficiency and simple black-box character. It is well known, however, that TDDFT notoriously underestimates energies of charge-transfer excited states which are prominent in phosphorescent metal–organic compounds. In this study, we investigate whether TDDFT is providing a reliable description of the electronic properties in these systems. To this end, we compute 0–0 triplet state energies for a series of 17 pseudo-square planar platinum( II ) and pseudo-octahedral iridium( III ) complexes that are known to feature quite different localization characteristics ranging from ligand-centered (LC) to metal-to-ligand charge transfer (MLCT) transitions. The calculations are performed with conventional semi-local and hybrid functionals as well as with optimally tuned range-separated functionals that were recently shown to overcome the charge transfer problem in TDDFT. We compare our results against low temperature experimental data and propose a criterion to classify excited states based on wave function localization. In addition, singlet absorption energies and singlet–triplet splittings are evaluated for a subset of the compounds and are also validated against experimental data. Our results indicate that for the investigated complexes charge-transfer is much less pronounced than previously believed.
机译：发光有机化金属配合物在过去发现广泛使用。这些化合物的计算建模通常基于时间依赖的密度泛函理论（TDDFT），其由于其数值效率和简单的黑匣子特性而享有普及。然而，众所周知，TDDFT众所周知地低估了在磷光金属 - 有机化合物中突出的电荷转移激发态的能量。在本研究中，我们研究了TDDFT是否提供了这些系统中电子特性的可靠描述。为此，我们计算0-0三重态能量，用于一系列17伪方形平面铂（II）和伪八面体铱（III）复合物，该份人已知具有相当不同的定位特性，从而居中地（LC ）金属到配体电荷转移（MLCT）过渡。使用传统的半局部和混合功能以及最近显示的最佳调整范围分离功能进行计算，该功能最近被示出克服TDDFT中的电荷传递问题。我们将结果与低温实验数据进行比较，并提出基于波函数定位对激发状态进行分类的标准。另外，对化合物的子集评价单线态吸收能量和单线三重态分裂，并且还针对实验数据验证。我们的结果表明，对于调查的复合物，电荷转移比以前认为的要约较小。

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