Cheng Meixin, Rivas Nicolás, Lim Su Ji, Pichugin Kostyantyn, Petruk Ariel A, Klinkova Anna, Smith Rodney, Hopkins W Scott, Sciaini Germán
Department of Chemistry, and Waterloo Institute for Nanotechnology , University of Waterloo , 200 University Avenue W. , Waterloo , ON N2L 3G1 , Canada.
J Phys Chem Lett. 2019 Oct 3;10(19):5742-5747. doi: 10.1021/acs.jpclett.9b01712. Epub 2019 Sep 16.
Multiply charged anions (MCAs) display unique photophysics and solvent-stabilizing effects. Well-known aqueous species such as SO and PO experience spontaneous electron detachment or charge-separation fragmentation in the gas phase owing to the strong Coulomb repulsion arising from the excess of negative charge. Thus, anions often present low photodetachment thresholds and the ability to quickly eject electrons into the solvent via charge-transfer-to-solvent (CTTS) states. Here, we report spectroscopic evidence for the existence of a repulsive Coulomb barrier (RCB) that blocks the ejection of "CTTS-like" electrons of the aqueous BF dianion. Our spectroscopic experimental and theoretical studies indicate that despite the exerted Coulomb repulsion by the nascent radical monoanion BF, the photoexcited electron remains about the BF core. The RCB is an established feature of the potential energy landscape of MCAs in vacuo, which seems to extend to the liquid phase highlighting recent observations about the dielectric behavior of confined water.
多电荷阴离子（MCAs）表现出独特的光物理性质和溶剂稳定效应。诸如SO和PO等著名的水相物种在气相中会由于过量负电荷产生的强库仑排斥而经历自发电子脱离或电荷分离碎片化。因此，阴离子通常具有低光脱离阈值以及通过电荷转移至溶剂（CTTS）态将电子快速喷射到溶剂中的能力。在此，我们报告了存在一个排斥性库仑势垒（RCB）的光谱学证据，该势垒阻止了水相BF二价阴离子的“类CTTS”电子的喷射。我们的光谱实验和理论研究表明，尽管新生自由基单阴离子BF施加了库仑排斥，但光激发电子仍保留在BF核周围。RCB是真空中MCAs势能面的一个既定特征，它似乎延伸到了液相，突出了最近关于受限水介电行为的观察结果。
