We review the binding and energy level alignment of π-conjugated systems on metals, a field which during the last two decades has seen tremendous progress both in terms of experimental characterization as well as in the depth of theoretical understanding. Precise measurements of vertical adsorption distances and the electronic structure together with ab-initio calculations have shown that most of the molecular systems have to be considered as intermediate cases between weak physisorption and strong chemisorption. In this regime, the subtle interplay of different effects such as covalent bonding, charge transfer, electrostatic and van der Waals interactions yields a complex situation with different adsorption mechanisms. In order to establish a better understanding of the binding and the electronic level alignment of π-conjugated molecules on metals, we provide an up-to-date overview of the literature, explain the fundamental concepts as well as the experimental techniques and discuss typical case studies. Thereby, we relate the geometric with the electronic structure in a consistent picture and cover the entire range from weak to strong coupling.

中文翻译：

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金属上 π 共轭系统的结合和电子水平对齐

我们回顾了金属上 π 共轭系统的结合和能级对齐，这个领域在过去的二十年里在实验表征和理论理解的深度方面都取得了巨大的进步。垂直吸附距离和电子结构的精确测量以及从头计算表明，大多数分子系统必须被视为弱物理吸附和强化学吸附之间的中间情况。在这种情况下，共价键合、电荷转移、静电和范德华相互作用等不同效应的微妙相互作用产生了具有不同吸附机制的复杂情况。为了更好地理解金属上π共轭分子的结合和电子能级排列，我们提供了最新的文献综述，解释了基本概念和实验技术，并讨论了典型案例学习。因此，我们在一致的图片中将几何与电子结构联系起来，并涵盖了从弱耦合到强耦合的整个范围。