Department of Chemistry, Marquette University, Milwaukee, WI, 53201-1881, USA.
Angew Chem Int Ed Engl. 2017 Jan 2;56(1):266-269. doi: 10.1002/anie.201609695. Epub 2016 Nov 29.
In cases of coherent charge-transfer mechanism in biaryl compounds the rates follow a squared cosine trend with varying dihedral angle. Herein we demonstrate using a series of biaryl cation radicals with varying dihedral angles that the hole stabilization shows two different regimes where the mechanism of the hole stabilization switches over from (static) delocalization over both aryl rings to (dynamic) hopping. The experimental data and DFT calculations of biaryls with different dihedral angles unequivocally support that a crossover from delocalization to hopping occurs at a unique dihedral angle where the electronic coupling (H ) is one half of reorganization (λ), that is, H =λ/2. The implication of this finding in non-coherent charge-transfer rates is being investigated.
在双芳基化合物中，当发生相干电荷转移机制时，速率随二面角的变化呈现平方余弦趋势。在此，我们通过一系列具有不同二面角的双芳基阳离子自由基证明，空穴稳定化表现出两种不同的状态，其中空穴稳定化的机制从两个芳环上的（静态）离域转变为（动态）跳跃。不同二面角的双芳基的实验数据和 DFT 计算明确支持这样一种观点，即从离域到跳跃的转变发生在电子耦合（H）是重组（λ）的一半的独特二面角处，即 H =λ/2。正在研究这一发现对非相干电荷转移速率的影响。
