Verma Pooja, Ghosh Debashree, Dutta Achintya Kumar
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata 700032, India.
J Phys Chem A. 2021 Jun 10;125(22):4683-4694. doi: 10.1021/acs.jpca.0c10199. Epub 2021 May 28.
We present an EOM-CCSD-based quantum mechanical/molecular mechanical (QM/MM) study on the electron attachment process to solvated cytosine. The electron attachment in the bulk solvated cytosine occurs through a doorway mechanism, where the initial electron is localized on water. The electron is subsequently transferred to cytosine by the mixing of electronic and nuclear degrees of freedom, which occurs on an ultrafast time scale. The bulk water environment stabilizes the cytosine-bound anion by an extensive hydrogen-bond network and drastically enhances the electron transfer rate from that observed in the gas phase. Microhydration studies cannot reproduce the effect of the bulk water environment on the electron attachment process, and one needs to include a large number of water molecules in the calculation to obtain converged results. The predicted adiabatic electron affinity and electron transfer rate obtained from our QM/MM calculations are consistent with the available experimental results.
我们展示了一项基于方程-of-motion耦合簇单双激发（EOM-CCSD）的量子力学/分子力学（QM/MM）研究，该研究针对电子附着到溶剂化胞嘧啶的过程。在大量溶剂化胞嘧啶中的电子附着通过一种门道机制发生，其中初始电子定域在水上。随后，电子通过电子和核自由度的混合转移到胞嘧啶上，这发生在超快时间尺度上。大量水环境通过广泛的氢键网络稳定胞嘧啶结合的阴离子，并极大地提高了与气相中观察到的相比的电子转移速率。微水合研究无法重现大量水环境对电子附着过程的影响，并且需要在计算中包含大量水分子以获得收敛结果。我们的QM/MM计算得到的预测绝热电子亲和势和电子转移速率与现有的实验结果一致。
