Dynamics of charge transfer in self-assembled monomolecular films

该项目的主要目标是系统地研究分子电子学(ME)潜在构件和组件中的飞秒电荷转移(CT)动力学，以获得关于最相关参数的定量数据--作为理论和分子设计的宝贵输入--并更好地理解潜在的过程。为此，我们将应用基于同步加速器的共振俄歇电子能谱(RAES)与芯孔时钟(CHC)相结合的方法来研究目标分子在导电衬底上的单分子组装。上述方法依赖于将合适的RAES谱分解成与激发态的标准衰变和共振激发电子对衬底的CT有关的部分。它是无接触的，并且使用在俄歇过程中出现的内壳空位的已知寿命作为内部时间基准。由于靶分子的特殊设计，CT通路将由尾基(丁腈等)的共振激发来明确定义。连接到分子骨架上，分子骨架又将通过合适的头基连接到底物上。与项目的第一部分(ZH 63/14-1)相比，我们打算(I)通过选择诸如反向CT等特殊和有限的情况来测试RAES-CHC方法的适用范围，(Ii)获得关于潜在分子线的更广泛的信息，(Iii)阐明锚基对CT动力学的贡献，并在可能的情况下，为其最佳选择提供建议，(Iv)测试潜在的分子电子器件，如无取代整流器(基于蔚蓝的化合物)和光驱动开关(基于偶氮苯的化合物)，以及(V)将RAES-CHC方法扩展到新系统。我们将特别关注分子轨道选择CT动力学的研究，这可以在RAES-CHC方法中通过能量选择或对称选择来解决，正如我们在项目的第一部分(ZH 63/14-1)所展示的那样。CT动力学实验将伴随着静态CT测量(使用水银滴法)，以获得目标系统和ME其他构件中CT现象的一致和全面的图像。

The main objective of the project is a systematic study of femtosecond charge transfer (CT) dynamics in potential building blocks and components of molecular electronics (ME) to get quantitative data on the most relevant parameters - as valuable input for theory and molecular design - and to achieve a better understanding of the underlying processes. To this end, we will apply synchrotron-based resonance Auger electron spectroscopy (RAES) in combination with the core hole clock (CHC) method to the monomolecular assembles of the target molecules on conductive substrates. The above approach relies on decomposition of the suitable RAES spectra into the parts related to the standard decay of the excited state and CT of the resonantly excited electron to the substrate. It is contact-free and uses the known lifetime of inner shell vacancy, appearing in the course of the Auger process, as an internal time reference. Due to the special design of the target molecules, the CT pathway will be unambiguously defined by the resonant excitation of the tail group (nitrile, etc.) attached to the molecular backbone which, in its turn, will be attached to the substrate by a suitable head group. As compared to the first part of the project (ZH 63/14-1), we intend (i) to test the applicability range of the RAES-CHC approach by selection of special and limiting cases such as reverse CT, etc, (ii) to get broader information on potential molecular wires, (iii) to clarify the contribution of the anchor group to CT dynamics and, if possible, to give recommendation for its optimal choice, (iv) to test the potential molecular electronics devices such as substitution-free rectifiers (azulene-based compounds) and light-driven switches (azobenzene-based compounds), and (v) to extend the RAES-CHC approach to new systems. A special attention will be put on the study of molecular-orbital-selective CT dynamics which can be addressed within the RAES-CHC approach by either energy or symmetry selection, as shown by us during the first part of the project (ZH 63/14-1). The CT dynamics experiments will be accompanied by the measurements of static CT (using the mercury drop method) to obtain a consistent and comprehensive picture of CT phenomena in the target systems and other building blocks of ME.