Ruan Zilin, Ye Liping, Singh Yogendra, Naumann Tim, Kang Faming, Liu Ye, Mastalerz Michael, Gottfried J Michael
Department of Chemistry, Philipps University Marburg, 35037, Marburg, Germany.
Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, 69120, Heidelberg, Germany.
Angew Chem Int Ed Engl. 2025 Aug 11;64(33):e202504707. doi: 10.1002/anie.202504707. Epub 2025 Jul 9.
Isosteric replacement of CH units of acenes by nitrogen induces significant changes in their electronic, redox, and spectroscopic properties. Here, we describe the on-surface synthesis of a nonacene analogue substituted with four nitrogen atoms on a Au(111) surface by a two-step atom manipulation, employing a bis vinylene-bridged precursor synthesized in solution. The generated tetraazanonacene has been investigated by scanning tunnelling microscopy/spectroscopy (STM/STS) and noncontact atomic force microscopy (nc-AFM), combined with first-principles calculations. We found that, compared to the pristine nonacene, the electronegative nitrogen atoms lower the frontier orbitals, resulting in an increased STS transport gap of 1.49 eV. Furthermore, the formation of four pyridine-like rings induces a stronger modulation of the aromaticity in tetraazanonacene compared to substitution patterns where nitrogen atoms form pyrazine-like rings. This observation is different from the nucleus independent chemical shift investigation of previous reported tetraazaundecacene, for which a stronger open-shell character is expected. Our work provides access to the synthesis of extended azaacenes and to an understanding of their properties.
将并苯的CH单元用氮进行等排取代会使其电子、氧化还原和光谱性质发生显著变化。在此，我们描述了通过两步原子操纵在Au(111)表面上合成一种在四个位置被氮原子取代的并九苯类似物的过程，该过程采用了在溶液中合成的双亚乙烯基桥连前体。通过扫描隧道显微镜/光谱（STM/STS）和非接触原子力显微镜（nc-AFM），并结合第一性原理计算，对生成的四氮并九苯进行了研究。我们发现，与原始并九苯相比，电负性的氮原子降低了前沿轨道，导致STS传输能隙增加到1.49电子伏特。此外，与氮原子形成类似吡嗪环的取代模式相比，四个类似吡啶环的形成对四氮并九苯的芳香性产生了更强的调制作用。这一观察结果与先前报道的四氮并十一苯的核独立化学位移研究不同，后者预期具有更强的开壳特征。我们的工作为扩展氮杂并苯的合成及其性质的理解提供了途径。
