Department of Chemistry, University of Sheffield, Sheffield S3 7HF, UK.
Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, UK.
Nat Chem. 2017 Nov;9(11):1099-1104. doi: 10.1038/nchem.2793. Epub 2017 Jun 19.
Ultrafast electron transfer in condensed-phase molecular systems is often strongly coupled to intramolecular vibrations that can promote, suppress and direct electronic processes. Recent experiments exploring this phenomenon proved that light-induced electron transfer can be strongly modulated by vibrational excitation, suggesting a new avenue for active control over molecular function. Here, we achieve the first example of such explicit vibrational control through judicious design of a Pt(II)-acetylide charge-transfer donor-bridge-acceptor-bridge-donor 'fork' system: asymmetric C isotopic labelling of one of the two -C≡C- bridges makes the two parallel and otherwise identical donor→acceptor electron-transfer pathways structurally distinct, enabling independent vibrational perturbation of either. Applying an ultrafast UV(excitation)-IR(perturbation)-IR(monitoring) pulse sequence, we show that the pathway that is vibrationally perturbed during UV-induced electron transfer is dramatically slowed down compared to its unperturbed counterpart. One can thus choose the dominant electron transfer pathway. The findings deliver a new opportunity for precise perturbative control of electronic energy propagation in molecular devices.
凝聚相分子体系中的超快电子转移通常与分子内振动强烈耦合，这种振动可以促进、抑制和定向电子过程。最近探索这一现象的实验证明，光诱导电子转移可以通过振动激发得到强烈调制，这为分子功能的主动控制开辟了新途径。在这里，我们通过巧妙设计一个 Pt(II)-乙炔化物电荷转移给体-桥-受体-桥-给体“叉”系统，实现了这种明确的振动控制的首例：两个 -C≡C- 桥之一的不对称 C 同位素标记使两个平行且其他方面相同的给体-受体电子转移途径在结构上有所不同，从而可以独立地对任何一个进行振动扰动。通过应用超快 UV（激发）-IR（扰动）-IR（监测）脉冲序列，我们表明在 UV 诱导电子转移过程中受到振动扰动的途径与未受扰动的途径相比明显减慢。因此，可以选择主导的电子转移途径。这一发现为在分子器件中精确控制电子能量传播提供了新的机会。
