Theoretical examination of picosecond phenol migration dynamics in phenylacetylene solution

The time-dependent dynamics of phenol dissolved in liquid phenylacetylene is theoretically investigated through first-principles calculations and molecular dynamics. By modeling the hydroxyl functional group with a Morse potential, the bond becomes site-sensitive, vibrating at distinct frequencies when bound at the phenylacetylene triple bond and aromatic ring. This can be exploited to simulate 2D-IR echo spectra using Fourier analysis. The resulting dynamics yields a phenol migration time between the two primary binding sites on phenylacetylene of 3–5 ps in excellent agreement with experiment. Furthermore, this study finds that the mechanism for this migration is strongly influenced by an indirect pathway, in contrast to prior experimental interpretation. The dynamics is found to be primarily dictated by van der Waals forces instead of hydrogen bonding forces, a conclusion that is supported by first principles