When considering the ultrafast vibrational dynamics of a molecular system, many of our presuppositions originate from Redfield theory’s secular approximation—this encompasses the time evolution of the system’s density operator by ignoring the phenomena that allow populations and coherences to transfer energy on ultrafast timescales. However, for much of the last two decades, vibrational coherence transfer in metal carbonyl complexes has stood as a notable exception to the secular approximation of Redfield theory. First studied in rhodium and iridium dicarbonyl complexes and later found in more complicated systems such as dimanganese decacarbonyl and diiron hexacarbonyl dithiolates, vibrational coherence transfer offers valuable information about the ultrafast vibrational dynamics of metal carbonyl systems. As an experimentally observable phenomenon, vibrational coherence transfer provides considerable insight into the energy relaxation processes found among these complexes’ metal carbonyl modes that would otherwise be indeterminable under the secular approximation of Redfield theory. The insights gained from understanding vibrational coherence transfer pathways mechanistically is an invaluable tool for ultrafast spectroscopists moving forward. Therefore, using two-dimensional infrared (2D-IR) spectroscopy, we aim to investigate vibrational coherence transfer in a series of alkynyl dicobalt hexacarbonyl complexes that serve as intermediate species for Pauson-Khand catalysis reactions. By studying this synthetically diverse series of complexes with respect to different ligand structures and solvent environments, we hope to further uncover the relationships between molecular structure, system-bath interactions, and vibrational coherence transfer in a catalytically relevant system.

Alkynyl dicobalt hexacarbonyl complexes as a platform for investigating vibrational coherence transfer phenomena

ACS Fall 2021

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