Centre for Research in Molecular Modeling (CERMM) and Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, Canada H4B 1R6.
J Phys Chem A. 2013 Aug 15;117(32):7595-605. doi: 10.1021/jp403586u. Epub 2013 Jul 18.
Photoexcitation of iodide-acetonitrile clusters, I(-)(CH3CN)n, to the charge-transfer-to-solvent (CTTS) state and subsequent cluster relaxation could result in the possible formation of cluster analogues of the bulk solvated electron. In this work, the relaxation process of the CTTS excited iodide-acetonitrile binary complex, [I(-)(CH3CN)], is investigated using rigorous ab initio quantum chemistry calculations and direct-dynamics simulations to gain insight into the role and motion of iodine and acetonitrile in the relaxation of CTTS excited I(-)(CH3CN)n. Computed potential energy curves and profiles of the excited electron vertical detachment energy for [I(-)(CH3CN)] along the iodine-acetonitrile distance coordinate reveal for the first time significant dispersion effects between iodine and the excited electron, which can have a significant stabilizing effect on the latter. Results of direct-dynamics simulations demonstrate that [I(-)(CH3CN)]* undergoes dissociation to iodine and acetonitrile fragments, resulting in decreased stability of the excited electron. The present work provides strong evidence of solvent translational motion and iodine ejection as key aspects of the early time relaxation of CTTS excited I(-)(CH3CN)n that can also have a substantial impact on the subsequent electron solvation processes and further demonstrates that intricate details of the relaxation process of CTTS excited iodide-polar solvent molecule clusters make it heavily solvent-dependent.
碘化物-乙腈团簇的光激发，I(-)(CH3CN)n，到电荷转移到溶剂（CTTS）态，随后的团簇弛豫，可能导致体相溶剂化电子的团簇类似物的形成。在这项工作中，使用严格的从头算量子化学计算和直接动力学模拟研究了 CTTS 激发的碘化物-乙腈二元复合物，[I(-)(CH3CN)]*，以深入了解碘和乙腈在 CTTS 激发的 I(-)(CH3CN)n 弛豫中的作用和运动。计算的势能曲线和激发电子垂直离解能的轮廓[I(-)(CH3CN)]*沿碘-乙腈距离坐标，首次揭示了碘和激发电子之间显著的色散效应，这对后者有显著的稳定作用。直接动力学模拟的结果表明，[I(-)(CH3CN)]*经历解离为碘和乙腈片段，导致激发电子的稳定性降低。本工作为 CTTS 激发的 I(-)(CH3CN)n 的早期弛豫过程中溶剂平移运动和碘喷射作为关键方面提供了有力的证据，这也会对随后的电子溶剂化过程产生实质性影响，进一步证明了 CTTS 激发的碘-极性溶剂分子团簇的弛豫过程的复杂细节使其严重依赖于溶剂。
