Karilainen Topi, Cramariuc Oana, Kuisma Mikael, Tappura Kirsi, Hukka Terttu I
Department of Physics, Tampere University of Technology, Tampere, Finland.
J Comput Chem. 2015 Apr 5;36(9):612-21. doi: 10.1002/jcc.23834. Epub 2015 Jan 8.
The interplay between electrostatic and van der Waals (vdW) interactions in porphyrin-C60 dyads is still under debate despite its importance in influencing the structural characteristics of such complexes considered for various applications in molecular photovoltaics. In this article, we sample the conformational space of a porphyrin-C60 dyad using Car-Parrinello molecular dynamics simulations with and without empirical vdW corrections. Long-range vdW interactions, which are poorly described by the commonly used density functional theory functionals, prove to be essential for a proper dynamics of the dyad moieties. Inclusion of vdW corrections brings porphyrin and C60 close together in an orientation that is in agreement with experimental observations. The structural differences arising from the vdW corrections are shown to be significant for several properties and potentially less important for others. Additionally, our Mulliken population analysis reveals that contrary to the common belief, porphyrin is not the primary electron donating moiety for C60 . In the considered dyad, fullerene's affinity for electrons is primarily satisfied by charge transfer from the amide group of the linker. However, we show that in the absence of another suitable bound donor, C60 can withdraw electrons from porphyrin if it is sufficiently close.
尽管卟啉 - C60二元体系中静电相互作用和范德华（vdW）相互作用之间的相互作用在影响此类复合物的结构特征方面具有重要意义，而这些复合物在分子光伏的各种应用中被考虑，但关于它们之间的相互作用仍存在争议。在本文中，我们使用带有和不带有经验vdW校正的Car - Parrinello分子动力学模拟对卟啉 - C60二元体系的构象空间进行采样。常用的密度泛函理论泛函对长程vdW相互作用描述不佳，但事实证明长程vdW相互作用对于二元体系各部分的适当动力学至关重要。包含vdW校正会使卟啉和C60以与实验观察结果一致的取向靠近在一起。vdW校正引起的结构差异对几种性质显示出显著影响，而对其他性质可能不太重要。此外，我们的Mulliken布居分析表明，与普遍看法相反，卟啉不是C60的主要电子供体部分。在所考虑的二元体系中，富勒烯对电子的亲和力主要通过连接体酰胺基团的电荷转移来满足。然而，我们表明，如果没有另一个合适的结合供体，当C60足够接近时，它可以从卟啉中提取电子。
