Mixed-valent macrocyclic ruthenium complexes as conductive, molecular loops

本项目主要有两个目标：1)合成和全面研究具有强电子耦合的混合价氧化态大环三、四钌配合物。为此，我们将采用自互补的单钌配合物构建单元，具有半可溶的杂环螯合配体，在乙基和各自的螯合、配位功能之间提供不间断的偶联。2)直接评估这些分子导电回路的电导率。对于这些实验，我们将采用自制的，基于stm的单分子测量装置，我们根据我们尊敬的同事Latha Venkataraman的建造计划制作。该仪器于2019年成功投入运行，并提供了与该领域专家组获得的结果相当的结果。为此，我们将使用项目1中锚基团修饰的大环配合物，以及文献中已知的具有混合价态高电荷离域的新锚基团修饰的大环衍生物。锚基团是确保测试分子与STM装置的纳米级金电极结合所必需的。这将使我们能够成功地解决以下基本问题：通过空间或通过化学键的电子耦合如何与分子水平上的电荷传输效率进行比较，以及两种传导途径的可用性是否使金属环结构优于它们的线性类似物。在一个强大的合成组中，STM断结设置的可用性和成功实施使我们处于一个理想的位置，以解决这些基本的和大部分未解决的问题。如果成功，这个项目将使我们在分子电导界的最前沿。

This project has two main goals: 1) The synthesis and comprehensive investigation of macrocyclic tri- and tetraruthenium complexes with strong electronic coupling in their mixed-valent oxidation states. For this purpose, we will employ self-complementary monoruthenium complex building blocks with hemilabile, heterocyclic chelate ligands, which offer uninterrupted pi-conjugation between the ethynyl group and the respective chelating, coordinating functionality. 2) The direct assessment of the electrical conductivity of these molecular, conductive loops. For these experiments, we will employ a home-built, STM-based setup for single molecule measurements that we fabricated according to the construction plan of our esteemed colleague Latha Venkataraman. This instrumentation was successfully put into operation in 2019 and has provided results that equal those obtained by expert groups in this field. To these ends, we will use anchor group-modified, macrocyclic complexes from project 1) as well as new anchor-group-modified derivatives of literature-known macrocycles with proven, high charge delocalization in mixed-valent states. The anchor groups are required to ensure that the test molecules bind to the nanoscale gold electrodes of the STM setup. This will put us into a position to successfully address the fundamental questions of how electronic coupling through space or through chemical bonds compare with regard to the efficiency of charge transport at the molecular level and whether the availability of two conduction paths makes metallacyclic structures superior to their linear analogs. The availability and successful implementation of a STM break junction setup in a strong synthetic group puts us in an ideal position to tackle such fundamental and largely unanswered questions. If successful, this project will put us at the forefront within the molecular conductance community.