Excited-state dynamics study of organic and organometallic compounds using time-resolved spectroscopy

Abstract

In this dissertation, I intend to provide insight into the regulation of chemical reactions based on the excited-state dynamics of organic and organometallic compounds revealed using femtosecond transient absorption spectroscopy. First, it was revealed that charge transfer (CT) can be induced by electronic state mixing (ESM) in a pyrene derivative in which electron donors and acceptors are not resolvable. This study presents that a molecule without CT can be turned into another molecule with CT induced by ESM and demonstrate that the excited-state relaxation dynamics can be regulated through the ESM induced by introducing the substituents or changing the environmental factors such as solvent polarities. Second, proton-coupled electron transfer (PCET) of an Ir complex in an aprotic solvent and a protic solvent was studied. Femtosecond time-resolved spectroscopic data revealed that solvent-modulated PCET occurs in which the order of CT and proton transfer (PT) is reversed depending on the solvent. In addition, it has been shown that the efficiency of CT increases when PT precedes the charge transfer. This finding demonstrates the potential to control the PCET reaction in the desired direction and the efficiency of CT by simply perturbing the external hydrogen-bonding network with the solvent.