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

在这项由化学系化学结构、动力学和机制B项目资助的项目中，西北大学的陈林教授和北卡罗来纳州立大学的Felix Castellano教授正在开发光谱和合成方法，以研究过渡金属络合物(TMC)中的多个金属中心如何协同作用，将来自太阳光的能量转化和积累到多个电子势能，最终驱动催化反应生成燃料。这项拟议的研究符合美国国家科学基金会的战略和绩效目标，即为社会变革前沿和创新。通过拟议的研究获得的知识可能会对化学科学产生革命性的影响，并将极大地提高我们合理设计用于催化、光电子学和能源可持续性的化学材料/器件的能力。研究活动邀请大学研究生使用先进的激光设备进行表征和使用先进的化学实验室设备进行材料合成，为他们提供发展多学科专业知识的独特培训基础。下一代STEM劳动力迫切需要这样的培训，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/教育活动与针对年轻科学家的公众推广和指导相结合，包括大学内外的本科生(特别是女性、少数族裔和代表性不足的当地大学生)，通过协作培训、暑期学校和以教育为重点的研讨会。这项工作旨在通过工程结构因素在电子水平上控制材料过程，在相干电子和原子运动的时间尺度上影响分子内电子相互作用和体系-浴相互作用。新发展的二维电子光谱(2DES)和光学各向异性光谱应用于新的分子结构，将研究使多电子转化成为可能的机理细节。这项工作旨在了解多金属中心TMC之间的本征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，如铂之间的距离以及配体的空间位阻/能量/大小/共轭，来设计一系列双铂配合物的本征相干运动，导致分子轨道能级的系统变化。研究人员将使用外部微扰，即激光脉冲，在比基态铂-铂拉伸周期更快的时间尺度上移动电子密度，并随后通过瞬时光学各向异性对偶极关联进行系统研究，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含义。

In this project funded by Chemical Structure, Dynamics and Mechanisms B 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.