Buttarazzi Edoardo, Perrella Fulvio, Rega Nadia, Petrone Alessio
Scuola Superiore Meridionale, Largo San Marcellino 10, I-80138 Napoli, Italy.
Department of Chemical Sciences, University of Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia 21, I-80126 Napoli, Italy.
J Chem Theory Comput. 2023 Dec 12;19(23):8751-8766. doi: 10.1021/acs.jctc.3c00855. Epub 2023 Nov 22.
Here is presented the ultrafast hole-electron dynamics of photoinduced metal to ligand charge-transfer (MLCT) states in a Ru(II) complex, [Ru(dcbpy)(NCS)] (dcbpy = 4,4'-dicarboxy-2,2'-bipyridine), a photoactive molecule employed in dye sensitized solar cells. Via cutting-edge computational techniques, a tailored computational protocol is here presented and developed to provide a detailed analysis of the electronic manifold coupled with nuclear vibrations to better understand the nonradiative pathways and the resulting overall dye performances in light-harvesting processes (electron injection). Thus, the effects of different vibrational modes were investigated on both the electronic levels and charge transfer dynamics through a theoretical-computational approach. First, the linear response time-dependent density functional (LR-TDDFT) formalism was employed to characterize excitation energies and spacing among electronic levels (the electronic layouts). Then, to understand the ultrafast (femtosecond) charge dynamics on the molecular scale, we relied on the nonperturbative mean-field quantum electronic dynamics via real-time (RT-) TDDFT. Three vibrational modes were selected, representative for collective nuclear movements that can have a significant influence on the electronic structure: two involving NCS ligands and one involving dcbpy ligands. As main results, we observed that such MLCT states, under vibrational distortions, are strongly affected and a faster interligand electron transfer mechanism is observed along with an increasing MLCT character of the adiabatic electronic states approaching closer in energy due to the vibrations. Such findings can help both in providing a molecular picture of multidimensional vibro-electronic spectroscopic techniques, used to characterize ultrafast coherent and noncoherent dynamics of complex systems, and to improve dye performances with particular attention to the study of energy or charge transport processes and vibronic couplings.
本文展示了一种钌（II）配合物[Ru(dcbpy)(NCS)]（dcbpy = 4,4'-二羧基-2,2'-联吡啶）中光诱导金属到配体电荷转移（MLCT）态的超快空穴-电子动力学，该配合物是一种用于染料敏化太阳能电池的光活性分子。通过前沿计算技术，本文提出并开发了一种定制的计算方案，以详细分析与核振动耦合的电子流形，从而更好地理解光捕获过程（电子注入）中的非辐射途径以及由此产生的整体染料性能。因此，通过理论计算方法研究了不同振动模式对电子能级和电荷转移动力学的影响。首先，采用线性响应含时密度泛函（LR-TDDFT）形式来表征激发能和电子能级之间的间距（电子布局）。然后，为了在分子尺度上理解超快（飞秒）电荷动力学，我们依靠通过实时（RT-）TDDFT的非微扰平均场量子电子动力学。选择了三种振动模式，它们代表了可能对电子结构有重大影响的集体核运动：两种涉及NCS配体，一种涉及dcbpy配体。作为主要结果，我们观察到这种MLCT态在振动畸变下受到强烈影响，并且随着绝热电子态由于振动而在能量上更接近，观察到配体间电子转移机制更快，同时MLCT特征增加。这些发现有助于提供多维振动-电子光谱技术的分子图景，该技术用于表征复杂系统的超快相干和非相干动力学，并且有助于改善染料性能，尤其关注能量或电荷传输过程以及振动-电子耦合的研究。
