David A. Blank, Principal Investigator

Excited State Intramolecular Proton Transfer Studies of 2-(2-Pyridyl)pyrrole in Solution

This group performed computational investigations of the excited state intramolecular proton transfer in 2-(2- pyridyl)pyrrole in solution. This molecule offers a model system where the geometry for the proton transfer is restricted compared with previous studies of hydrogen bonded dimers. The group employed both ab initio and semiempirical models for the solute and the SM5.42 implicit solvation model to examine the ground and excited states of both in 2-(2-pyridyl)pyrrole and the proton transfer state. They calculated absorption and fluorescence energies using the time-scale separation method developed by Truhlar and coworkers, where the vertical transition energy is obtained by allowing equilibration of only the electronic degrees of freedom in the final state. For example, the absorption maximum will reflect the energy difference between a fully-equilibrated ground state and the excited state calculated with the ground state reaction field where the electronic degrees of freedom have equilibrated in the excited state but the nuclear degrees of freedom remain frozen at the ground state configuration. Fluorescence was calculated from an equilibrated excited state and an electronically equilibrated ground state with a reaction field that reflected the excited state nuclear configuration. These computations will be used in conjunction with spectroscopic experiments to generate a complete picture of this model proton transfer system.

Research Group

Sarah Schmidtke, Graduate Student Researcher