Hydrogen bond dynamics of 9-fluorenone derivatives in water studied by two-dimensional infrared spectroscopy

Abstract

In solutions, a vibrational frequency of solute molecule is sensitive to changes of the solvent environment. Especially, in aqueous solution, hydrogen-bond making and breaking processes play an important role in the dynamics of water molecules surrounding the solute. For the past few decades, vibrational dynamics in aqueous solutions have been investigated by two-dimensional infrared (2D-IR) spectroscopy. 2D-IR spectroscopy is a powerful tool to obtain microscopic information in solution such as ultrafast solvent dynamics and local structure of solvent by probing the changes of vibrational frequency. In the present study, we performed 2D-IR spectroscopic measurements on 9-fluorenone-4-carboxylic acid (FL-4) and 9-fluorenone-2-carboxylic acid (FL-2, molecular structure is shown in Figure 1(a)) in aqueous solutions. By comparing the results of FL-4 and FL-2, we aim to find the relationship between molecular structure and vibrational dynamics.