Pylaeva Svetlana, Marx Patrick, Singh Gurjot, Kühne Thomas D, Roemelt Michael, Elgabarty Hossam
Dynamics of Condensed Matter and Center for Sustainable Systems Design, Chair of Theoretical Chemistry, University of Paderborn, Warburger Str. 100, Paderborn 33098, Germany.
Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
J Phys Chem A. 2021 Jan 28;125(3):867-874. doi: 10.1021/acs.jpca.0c11296. Epub 2021 Jan 19.
Recent experiments have shown that the organic free radical 1,3-bisdiphenylene-2-phenylallyl (BDPA) can induce an Overhauser effect dynamic nuclear polarization in insulating solids, a feat previously considered not to be possible. Here, we establish that this peculiar ability of the BDPA radical stems from its mixed-valence nature and the ensuing intramolecular charge transfer. Using state-of-the-art DMRGSCF calculations, we confirm the class II mixed-valence nature of BDPA with the characteristic double-well potential energy surface, and we investigate the mechanism of the consequent electron hopping. A two-component vibronic Hamiltonian is then employed to compute the rate of electron hopping from a quantum dynamical time-propagation of the density matrix. The predicted hyperfine coupling oscillations indeed fall within the frequency range required for an Overhauser effect. The paradigm of mixed-valence compounds as a mining source opens many possibilities for the development and fine tuning of novel polarizing agents.
最近的实验表明，有机自由基1,3 - 双亚苯基 - 2 - 苯基烯丙基（BDPA）能够在绝缘固体中诱导奥弗豪泽效应动态核极化，这一成果此前被认为是不可能实现的。在此，我们证实BDPA自由基的这种独特能力源于其混合价性质以及随之而来的分子内电荷转移。利用最先进的DMRGSCF计算方法，我们确认了BDPA具有特征性双阱势能面的II类混合价性质，并研究了随之产生的电子跳跃机制。然后采用双组分电子振动哈密顿量，通过密度矩阵的量子动力学时间传播来计算电子跳跃速率。预测的超精细耦合振荡确实落在奥弗豪泽效应所需的频率范围内。混合价化合物作为一种资源的范例为新型极化剂的开发和精细调谐开辟了许多可能性。
