Discipline: Chemistry and Chemical Sciences
Subcategory: Chemistry (not Biochemistry)
Jean L. Devera - University of the Virgin Islands
Co-Author(s): Antonio D. Brathwaite, University of the Virgin Islands, St. Thomas, VI Michael A. Duncan, University of Georgia, Athens, GA
Metal carbonyls are well-known molecules throughout chemistry and are used in metal purification, organic synthesis, homogeneous catalysis, polymerization chemistry, and drug development. Recently, metal carbonyl complexes have been studied in the gas phase with mass spectrometry and infrared laser photodissociation spectroscopy. Density Functional Theory (DFT) is often used to assign structures and aid in the interpretation of the experimental data. Spectra obtained from gas-phase experiments on neutrals and ions are ideal for such comparisons to theory. However, since vibrational frequencies calculated via DFT are harmonic, theoretical spectra do not perfectly coincide with experimental values. As a result, scaling factors are calculated to account for anharmonicity. Furthermore, the frequencies predicted by DFT calculations vary depending on the basis set and functional used. To obtain reliable and unbiased vibrational scaling factors for metal carbonyl systems, a systematic study is required. The aim of this project is to calculate scaling factors for different functional/ basis set combinations using DFT, by comparison to experimental data. Calculations were conducted on 20 metal carbonyl complexes using the Gaussian 09 program. Three basis sets: LanL2DZ, LanL2TZ, and Def2-TZVP were used for each of the four functionals: B3LYP, BP86, M06, and M06L and scaling factors were obtained for each basis set/functional combination. When the calculated scaling factors are implemented, theoretical bands are in excellent agreement with experimental bands. The vibrational scaling factors calculated in this study can be used by scientists and engineers when studying carbonyl stretches in various metal-carbonyl systems. Plans for future work include investigating the utility of this level of theory and computational method with other metal-ligand complexes such as metal-acetylene, metal-ethylene, and metalwater.
References: A. M. Ricks, Z.E. Reed, M.A. Duncan, ‘Infrared spectroscopy of mass-selected metal carbonyl cations,’ J. Mol. Spec. 266 (2011) 63.
J. P. Merrick, D. Moran, L. Radom, ‘An evaluation of harmonic vibrational frequency scale factors,’ J. Phys. Chem. A 111 (2007) 11683.
R. D. Johnson III, K. K. Irikawa, R. N. Kacker, R. Kessel, ‘Scaling factors and uncertainties for ab initio anharmonic vibrational frequencies,’ J. Chem. Theor. Comp. 6 (2010) 2822.
Funder Acknowledgement(s): The research was funded by an NSF/HBCU-UP RIA grant HRD-1505095 awarded to Dr. Antonio Brathwaite.
Faculty Advisor: Antonio Brathwaite,