Ad aurum: tunable transfer of N-heterocyclic carbene complexes to gold surfaces
Ad aurum: tunable transfer of N-heterocyclic carbene complexes to gold surfaces
复制标题
DOI：
10.1039/d2qi01941h
复制
发表时间：
2022-10-17
影响因子：
7
通讯作者：
Camden, Jon P.
中科院分区：
文献类型：
--
作者：
Dominique, Nathaniel L.;Chen, Ran;Camden, Jon P.
N-杂环卡宾(NHC)单分子膜在金表面和纳米颗粒(AuNPs)上的特殊稳定性使得从催化到生物医学的新的和多样化的应用成为可能。我们对NHC在表面上的反应性的了解；然而，与NHC配体在有机金属化学中悠久而丰富的历史相比，我们的理解是相当新的。在这项工作中，我们探索了在均相有机金属体系中用于NHC转移的已建立的转金属反应，以确定如何使用它们来创建卡宾功能化的金表面。测试了两类基于咪唑和苯并咪唑支架的NHC。用X射线光电子能谱(XPS)、激光解吸电离质谱仪(LDI-MS)和表面增强拉曼光谱(SERS)对所得AuNP表面进行了分析。Au(I)或Ag(I)异丙基苯并咪唑NHC络合物与柠檬酸封端的AuNPs反应，在这两种情况下，NHC都通过Au吸附原子被化学吸附。此外，理论计算还表明，通过Au吸附原子的结合比10kcal摩尔(-1)更有利，与实验很好地一致。令人惊讶的是，金(I)、银(I)和铜(I)二异丙基苯基咪唑NHC的反应不遵循相同的模式。铜络合物经历了转金属作用，只有很少的铜沉积；而出人意料的是，银络合物先于转金属作用，而是与AuNP加合，保留了Ag-C键。理论计算表明，咪唑配体与金表面具有显著的分散相互作用，这可能通过银吸附原子基序稳定结合，尽管它的成键能不那么有利。综上所述，这些结果表明了一种通过改变卡宾结构来调节反应性的独特能力，并提出了如何应用有机金属化学中已建立的转金属反应来形成NHC功能化表面的关键问题。
The exceptional stability of N-heterocyclic carbene (NHC) monolayers on gold surfaces and nanoparticles (AuNPs) is enabling new and diverse applications from catalysis to biomedicine. Our understanding of NHC reactivity at surfaces; however, is quite nascent when compared to the long and rich history of NHC ligands in organometallic chemistry. In this work, well-established transmetalation reactions, previously developed for NHC transfer in homogeneous organometallic systems, are explored to determine how they can be used to create carbene functionalized gold surfaces. Two classes of NHCs, based on imidazole and benzimidazole scaffolds, were tested. The resulting AuNP surfaces were analyzed using X-ray photoelectron spectroscopy (XPS), laser desorption ionization mass spectrometry (LDI-MS), and surface-enhanced Raman spectroscopy (SERS). Reaction of either a Au(i) or Ag(i) isopropyl benzimidazole NHC complex with citrate-capped AuNPs yields, in both cases, a chemisorbed NHC that is bound through a Au adatom. Theoretical calculations additionally illustrate that binding through the Au adatom is favored by more than 10 kcal mol(-1), in good agreement with experiments. Surprisingly, reaction of Au(i), Ag(i), and Cu(i) diisopropylphenyl imidazole NHCs do not follow the same pattern. The Cu complex undergoes transmetalation with very little deposition of Cu; whereas, unexpectedly, the Ag complex foregoes transmetalation and instead adducts to the AuNP with retention of the Ag-C bond. Theoretical calculations illustrate that the imidazole ligand affords significant dispersion interactions with the gold surface, which may stabilize binding through the Ag adatom motif, despite its less favorable bonding energies. Taken together these results suggest a unique ability to tune the reactivity by changing the carbene structure and raise critical questions about how established transmetalation reactions in organometallic chemistry can be applied to form NHC functionalized surfaces.