Collaborative Research: Investigating Structural Dynamic Coherences of Transition Metal Complexes in Photochemical Processes

本课题由化学系化学结构、动力学与机理项目资助，美国西北大学的林晨教授和北卡罗来纳州州立大学的费利克斯·卡斯特拉诺教授正在开发光谱和合成方法，以研究过渡金属络合物（TMC）中的多金属中心如何协同作用，将来自阳光的能量转化和积累为多个电子势能，最终将驱动催化反应，产生燃料。拟议的研究符合NSF的战略和绩效目标，以改变前沿和为社会创新。 通过拟议的研究获得的知识可能会对化学科学产生变革性影响，并将大大提高我们合理设计催化，光电子和能源可持续性化学材料/设备的能力。 该研究活动使大学研究生能够使用先进的激光设备进行表征，并使用先进的化学实验室设施进行材料合成，为他们提供了一个独特的培训基地，以发展多学科专业知识。 下一代STEM劳动力迫切需要这种培训，以探索化学科学的前沿，并保持美国在知识前沿的全球竞争力。拟议的研究/教育活动与针对青年科学家的公共宣传和辅导相结合，包括大学内外的本科生（特别是女性，少数民族和代表性不足的当地大学生）通过合作培训，暑期学校和教育为重点的专题讨论会。这项工作的目的是控制材料的过程在电子水平上的工程结构因素，以影响分子内相干电子和原子运动的时间尺度上的电子相互作用和系统浴相互作用将通过新开发的二维电子光谱（2DES）和应用于新分子结构的光学各向异性光谱来研究使多电子转换成为可能的机制细节。 该工作旨在了解多金属中心TMCs之间的内在电子耦合及其对光化学反应的影响。 这项工作将通过系统地改变结构因素，如铂间距离以及配体的空间位阻/能量学/尺寸/共轭，在一系列双铂络合物中设计固有的相干运动，从而导致分子轨道能级的系统变化。 研究人员将使用外部扰动，即激光脉冲，在比基态Pt-Pt拉伸周期更快的时间尺度上移动电子密度，并通过瞬态光学各向异性对偶极相关性进行系统研究，通过二维电子光谱进行电子耦合。 他们将进一步研究这些相干运动在化学和光化学过程中的影响。

In this project funded by Chemical Structure, Dynamics and Mechanisms program of Chemistry Division, Professors Lin Chen of Northwestern University and Felix Castellano of North Carolina State University are developing spectroscopic and synthetic methods to investigate how multiple metal centers in transition metal complexes (TMCs) act cooperatively to convert and accumulate energy from sunlight to multiple electronic potentials that ultimately will drive catalytic reactions for generating fuels. The proposed research is in line with the NSF Strategic and Performance Goals to transform the frontiers and innovate for society. The knowledge obtained through the proposed studies could be transformative for the chemical sciences and will greatly enhance our ability to rationally design chemical materials/devices for catalysis, optoelectronics and energy sustainability. The research activity engages university graduate students to use the advanced laser facility for characterization and advanced chemistry lab facilities for materials synthesis, providing them with a unique training ground for the development of multidisciplinary expertise. Such training is urgently needed for the next generation STEM workforce in order to explore the frontier of chemical science and to keep the US globally competitive at the frontiers of knowledge. The proposed research/education activities are integrated with public outreach and mentoring aimed at young scientists, including undergraduate students inside and outside of the University (especially female, minority, and underrepresented local college students) through collaborative training, summer school and education focused symposiums.This work aims at controlling materials processes at the level of electrons by engineering structural factors to influence intramolecular electronic interactions and system-bath interactions on the time scale of coherent electronic and atomic motions The mechanistic details enabling multiple-electron conversion will be investigated by newly developed two-dimensional electronic spectroscopy (2DES) and optical anisotropy spectroscopy applied to new molecular architectures. The proposed work aims at understanding intrinsic electronic couplings between the multiple metal centers TMCs and their influence on photochemical reactions. The work will engineer intrinsic coherent motions in a series of di-platinum complexes via systematically varying structural factors, such as the inter-platinum distances as well as the steric hindrance/energetics/size/conjugation of the ligands, resulting in systematic changes of the energy levels of the molecular orbitals. The researchers will use external perturbations, i.e. laser pulses, to shift electron density on a time scale faster than the period of the ground state Pt-Pt stretch, and follow with systematic investigations of dipole correlations by transient optical anisotropy, electronic couplings by two-dimensional electronic spectroscopy. They will further investigate the implications of these coherent motions in chemical and photochemical processes.