Collaborative Research: Ultrafast Excited State Electron and Nuclear Coherences in Transition Metal Dimer Complexes and Their Roles in Photochemistry

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In this project funded by the Chemical Structure, Dynamic & Mechanism B Program of the Chemistry Division, Professors Lin X. Chen and Felix N. Castellano are developing the spectroscopy and chemistry necessary for the study of transition metal complexes featuring dimetallic cooperativity. These targeted molecules convert and accumulate energy from sunlight that can ultimately drive photocatalytic reactions for generating fuels. The knowledge obtained through these studies could be transformative for the chemical sciences and will enhance our ability to rationally design chemical materials/devices for catalysis, optoelectronics and energy sustainability. The research engages university graduate students to use advanced laser spectroscopy for characterization, incorporates state-of-the-art computational chemistry for quantum mechanical and molecular dynamics modeling, and utilizes advanced chemistry laboratory facilities for molecular synthesis, providing them with an expansive training ground for the development of multidisciplinary expertise. Such training is urgently needed for the next generation STEM workforce in order to explore the frontiers of chemical science and to ensure US global competitiveness at the frontiers of scientific knowledge.The work studies quantum coherence in a series of di-metallic compounds, such as platinum, molybdenum, and tungsten dimer chromophores through systematic variation of structural factors. Mechanistic details enabling multiple-electron conversion processes are to be investigated through two-dimensional electronic spectroscopy and by the design of new molecular architectures. The research seeks an understanding of intrinsic electronic couplings between multiple metal centers in transition metal complexes and their influence on photochemical reactivity. Using ultrafast laser pulses as light sources, transient bond-making or bond-breaking processes will be induced between the two metal centers, which enable detailed studies on origins of their catalytic activities and fundamental reaction dynamics.