Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States.
J Am Chem Soc. 2017 Oct 4;139(39):13770-13778. doi: 10.1021/jacs.7b06283. Epub 2017 Sep 25.
Butadiene is the simplest polyene and has long served as a model system for many chemical and spectroscopic properties. However, this small molecule has presented significant challenges to theoretical chemistry. The 2A state, which is dark but photochemically important, is a prime source of this difficulty. Previous studies attributed the notorious difficulty in treating this state to strong double excitation character of the 2A state, which prevents the application of linear response (LR) methods. Therefore, one would require methods with much higher computational cost, especially for the analogues of this state in longer polyenes, and consequently studies of longer polyenes are very limited. In the present work, we argue that the difficulty stems more significantly from the inherently multiconfigurational character of the ground state. In addition, we validate the possibility of employing LR time-dependent density functional theory to investigate such a state with reasonable accuracy.
丁二烯是最简单的多烯，长期以来一直是许多化学和光谱性质的模型体系。然而，这种小分子给理论化学带来了很大的挑战。2A 态是暗态但光化学反应很重要，是这种困难的主要来源。先前的研究将这种状态难以处理的原因归结为 2A 态强烈的双激发特性，这阻止了线性响应（LR）方法的应用。因此，人们需要计算成本更高的方法，特别是对于更长多烯中这种状态的类似物，因此对更长多烯的研究非常有限。在本工作中，我们认为困难更多地源于基态固有的多组态特性。此外，我们验证了利用 LR 含时密度泛函理论以合理的精度研究这种状态的可能性。
