Dr. Richard L. Redington

Principal Research Interests

• Molecular Spectroscopy
• Quantum Tunneling
• Intermolecular Interactions

Professor Redington's research concerns applications of spectroscopy to gaseous, solvated, and matrix isolated molecules for the determination of properties including molecular geometries, potential energy functions, excitation energy transfer dynamics, and solvation effects. Substances capable of quantum mechanical tunneling between equivalent energy minima are of particular interest. Sample molecules may possess an intramolecular hydrogen bond such as that of tropolone, C7H602 (2-hydroxy-2,4,6-cycloheptatriene-l-one), or no H-bond at all - as for 1,3-cyclobutadiene.



As suggested in one-dimensional form in the figure, valence isomerization by cyclobutadiene involves heavy atom tunneling as well as thermal excitation. Tropolone is studied because it demonstrates an exceptionally large and varied range of vibrational state-specific tunneling splittings in its ground and first excited singlet electronic states. It has an equal double-minimum potential energy surface in each electronic state, and questions addressed by the research concern the tunneling paths and tunneling rates followed by the molecule as it interconverts between the equal energy minima when different molecular vibrations are excited. Is the tunneling mechanism for tropolone based on fast, impulsive, H atom transfer followed by a slow heavy atom relaxation; is it based on concerted H atom and heavy atom motion; is it based on other principles? Careful studies of isotopically labeled molecules (isotopomers) help resolve these basic questions.

Ab initio quantum mechanical calculations are now able to play a crucial role in guiding interpretations of experimental data and suggesting new experiments. Quantum computations are routinely performed on the sample molecules of interest to predict and to test various properties including relative conformational energies, vibrational force fields and spectra, internal rotation barriers, reaction transition states, and solvation effects.

Representative Publications

• "Isoelectronic Homologues and Isomers: Tropolone, 5-Azatropolone, 1-H-Azepine-4,5-dione, Saddle Points, and Ions," Redington, R.L.  J. Phys. Chem. A 2006, 110, 1600-1607.
• "18O Effects on the Infrared Spectrum and Skeletal Tunneling of Tropolone," Redington, R. L.; Redington, T.E.; Blake, T.A.; Sams, R.L.; Johnson, T.J.  J. Chem Phys. 2005, 122, 224311.
• "Implications of Comparative Spectral Doublets Observed for Neon-Isolated and Gaseous Tropolone(OH) and Tropolone(OD)," Redington, R. L.; Redington, T.E. J. Chem Phys. 2005, 122, 124304.
• "Theoretical Study of the Ground-State Gas-Phase Unimolecular Decomposition Channels of Propynoic Acid," Ndip, E.M.N.; Shukla, M.K.; Leszcynski, J; Redington, R.L.  J. Chem Phys. 2004, 100, 779.
• "N2-pressure broadened Q branch spikes and vibration-contortion-rotation effects in the high resolution FTIR spectrum of tropolone", Redington, R.L.; Sams, R.L.  Chem. Phys. 2002, 283, 135-151.
• "State-specific spectral doublets in the FTIR spectrum of gaseous tropolone", Redington, R.L.; Sams, R.L.  J. Phys. Chem. 2002, 106, 7494-7511.
• "H atom and heavy atom tunneling processes in tropolone", Redington, R.L.  J. Chem. Phys. 2000, 113, 2319-2335.
• "IR spectra of tropolone(OH) and troplone(OD)", Redington, R.L.; Redington, T.E.; Montgomery, J.M.  J. Chem. Phys. 2000, 113, 2304-2318.
• "Ab Initio Modeled Matrix Trapping Sites, PES Asymmetry, and Automerization in the Ar/Cyclobutadiene System", Redington, R.L.  J. Phys. Chem. A 2000, 104, 3806-3818.