Bischof Daniel, Radiev Yurii, Tripp Matthias W, Hofmann Philipp E, Geiger Thomas, Bettinger Holger F, Koert Ulrich, Witte Gregor
Fachbereich Physik, Philipps-Universität Marburg, Renthof 7, 35032 Marburg, Germany.
Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein Straße 4, 35043 Marburg, Germany.
J Phys Chem Lett. 2023 Mar 16;14(10):2551-2557. doi: 10.1021/acs.jpclett.3c00287. Epub 2023 Mar 6.
Halogenation of organic molecules causes chemical shifts of C1s core-level binding energies that are commonly used as fingerprints to identify chemical species. Here, we use synchrotron-based X-ray photoelectron spectroscopy and density functional theory calculations to unravel such chemical shifts by examining different partially fluorinated pentacene derivatives. Core-level shifts occur even for carbon atoms distant from the fluorination positions, yielding a continuous shift of about 1.8 eV with increasing degree of fluorination for pentacenes. Since also their LUMO energies shift markedly with the degree of fluorination of the acenes, core-level shifts result in a nearly constant excitation energy of the leading π* resonance as obtained in complementary recorded K-edge X-ray absorption spectra, hence demonstrating that local fluorination affects the entire π-system, including valence and core levels. Our results thus challenge the common picture of characteristic chemical core-level energies as fingerprint signatures of fluorinated π-conjugated molecules.
有机分子的卤化会导致C1s核心能级结合能发生化学位移，这些化学位移通常被用作识别化学物种的指纹。在此，我们使用基于同步加速器的X射线光电子能谱和密度泛函理论计算，通过研究不同的部分氟化并五苯衍生物来揭示这种化学位移。即使对于远离氟化位置的碳原子也会发生核心能级位移，随着并五苯氟化程度的增加，会产生约1.8 eV的连续位移。由于它们的最低未占分子轨道（LUMO）能量也会随着并苯的氟化程度而显著变化，核心能级位移导致在互补记录的K边X射线吸收光谱中获得的主导π*共振的激发能量几乎恒定，因此表明局部氟化会影响整个π体系，包括价电子和核心能级。因此，我们的结果挑战了将特征化学核心能级能量视为氟化π共轭分子指纹特征的常见观点。
