Electronic and Exchange Coupling in a Cross-Conjugated D–B–A Biradical: Mechanistic Implications for Quantum Interference Effects
作者:Martin L. Kirk、David A. Shultz、Daniel E. Stasiw、Diana Habel-Rodriguez、Benjamin Stein、Paul D. Boyle
DOI:10.1021/ja405354x
日期:2013.10.2
excited-state electronic structure of 1-meta. The results reveal important excited-state contributions to the ground-state singlet-triplet splitting in this cross-conjugated D-B-A biradical that contribute to our understanding of electronic coupling in cross-conjugated molecules and specifically to quantum interference effects. In contrast to the conjugated isomer, which is a D-B-A biradical possessing
对 Tp(Cum,Me)Zn(SQ-m-Ph-NN) (1-meta) 供体-桥-受体 (DBA) 进行了变温 EPR 光谱、电子吸收光谱和磁化率测量的组合) 双自由基,具有交叉共轭间亚苯基 (m-Ph) 桥和自旋单线态基态。实验结果已经在详细的键合和激发态计算的背景下进行了解释,以了解 1-meta 的激发态电子结构。结果揭示了对这种交叉共轭 DBA 双自由基中基态单线态-三重态分裂的重要激发态贡献,有助于我们理解交叉共轭分子中的电子耦合,特别是量子干涉效应。与共轭异构体相比,这是具有对亚苯基桥的 DBA 双自由基,将单个低位单激发 D→A 型构型混合到交叉共轭 DBA 双自由基基态中,对基态磁交换相互作用的贡献可以忽略不计。相反,由 Ph-NN (HOMO) → Ph-NN (LUMO) 单电子促进形成的激发态在构型上混合到 m-Ph 桥接 DA 双自由基的基态中。这导致双(动态)自旋极化机制成为