Jones Leighton O, Sadhukhan Tumpa, Schatz George C
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
ACS Phys Chem Au. 2022 Mar 18;2(4):277-281. doi: 10.1021/acsphyschemau.1c00055. eCollection 2022 Jul 27.
Surface chemistry is increasingly important for a number of applications, from catalysis to molecular qubits. For the qubit application, it is imperative that the energy levels of surface species involved in the process of interest are energetically distinct-that is addressable and not buried below or coincident with the substrate energy levels. One way to afford this is through chemical functionalization with derivatives that impart the property of choice to the interface. In this Letter, we report on the nature of the bond between a carbene moiety and an MoS surface. With density functional theory (DFT) and spin-polarized calculations, we first observe states in the band structure that pertain to the carbene group and then prove their origin. Importantly, we find localized π-states in the band gap that are due to π-electrons that are part of a diene attached to the carbene carbon and are not available in bonding configurations without the π conjugation. These lead to open-shell monocationic structures involving midgap HOMOs with densities on the carbene moiety. Both neutral and cationic forms of the carbenes are energetically separate from the MoS substrate, thus useful for optical manipulation. We explore several different choices of the carbene moieties, and show that those based on fused thiophene and bithiophene structures are the most favorable for localization, while purely carbon-based aromatic structures lead to states that are delocalized onto the MoS and thus less useful. These findings are potentially of interest to the design and synthesis of future molecular qubit candidates for device fabrication.
表面化学对于从催化到分子量子比特等众多应用而言愈发重要。对于量子比特应用，至关重要的是，参与相关过程的表面物种的能级在能量上是不同的，即能够被寻址，且不低于或与衬底能级重合。实现这一点的一种方法是通过用赋予界面所需特性的衍生物进行化学功能化。在本信函中，我们报告了卡宾部分与MoS表面之间键的性质。通过密度泛函理论（DFT）和自旋极化计算，我们首先在能带结构中观察到与卡宾基团相关的态，然后证明了它们的起源。重要的是，我们在带隙中发现了局域化的π态，这是由于与卡宾碳相连的二烯中的π电子所致，而在没有π共轭的键合构型中不存在这些π电子。这些导致了涉及带隙中间HOMO且在卡宾部分有密度的开壳单阳离子结构。卡宾的中性和阳离子形式在能量上均与MoS衬底分离，因此可用于光学操纵。我们探索了卡宾部分的几种不同选择，并表明基于稠合噻吩和联噻吩结构的卡宾最有利于局域化，而纯碳基芳香结构导致态离域到MoS上从而用处较小。这些发现对于未来用于器件制造的分子量子比特候选物的设计和合成可能具有重要意义。
