Dereka Bogdan, Maroli Nikhil, Poronik Yevgen M, Gryko Daniel T, Kananenka Alexei A
Department of Chemistry, University of Zurich CH-8057 Zurich Switzerland
Department of Physics and Astronomy, University of Delaware Newark Delaware 19716 USA.
Chem Sci. 2024 Aug 28;15(38):15565-76. doi: 10.1039/d4sc04797d.
Microscopic electric fields are increasingly found to play a pivotal role in catalysis of enzymatic and chemical reactions. Currently, the vibrational Stark effect is the main experimental method used to measure them. Here, we demonstrate how excited-state symmetry breaking can serve as a much more sensitive tool to assess these fields. Using transient infrared spectroscopy on a quadrupolar probe equipped with nitrile groups we demonstrate both its superior sensitivity and that it does not suffer from the notorious hydrogen-bond induced upshift of the C[triple bond, length as m-dash]N stretch frequency. In combination with conventional ground-state infrared absorption, excited-state symmetry breaking can be used to disentangle even weak specific hydrogen bond interactions from general field effects. We showcase this capability with the example of weak C-H hydrogen bonds in polar aprotic solvents. Additionally, we reveal for the first time symmetry breaking driven not by solvent but by the entropy of the pendant side chains of the chromophore. Our findings not only enhance our understanding of symmetry-breaking charge-transfer phenomena but pave the way toward using them in electric field sensing modality.
人们越来越发现微观电场在酶促反应和化学反应的催化过程中起着关键作用。目前，振动斯塔克效应是用于测量这些电场的主要实验方法。在此，我们展示了激发态对称性破缺如何能够作为一种更为灵敏的工具来评估这些电场。通过对配备有腈基的四极探针进行瞬态红外光谱分析，我们既证明了其卓越的灵敏度，又证明了它不会受到臭名昭著的氢键导致的C≡N伸缩频率上移的影响。结合传统的基态红外吸收，激发态对称性破缺可用于从一般场效应中分辨出甚至是微弱的特定氢键相互作用。我们以极性非质子溶剂中弱C-H氢键为例展示了这种能力。此外，我们首次揭示了对称性破缺不是由溶剂驱动的，而是由发色团侧链的熵驱动的。我们的发现不仅增进了我们对对称性破缺电荷转移现象的理解，还为在电场传感模式中使用这些现象铺平了道路。
