Theoretical Investigations of Novel Molecular Systems

My current research interest lies in the application of semi-empirical and ab initio molecular orbital theories to novel molecular systems.  Chemical systems that may be difficult to study experimentally can be easily examined theoretically with the available software.  Also, we can make theoretical predictions about the chemical behavior of a molecular system that experimentalists can then analyze.  Technology today allows these complex and time-consuming calculations to be performed efficiently on a typical desktop computer.  The available software (PC Spartan Plus, WinMopac, etc.) utilizes varying levels of theory to predict the geometrical and electronic structures of molecular species.  In addition to these properties, we are able to predict transition state geometries, vibrational frequencies, dipole moments, enthalpies of formation, as well as other properties.  In addition to these “static” calculations, we also have the ability study reaction processes (bond breaking and formation).  This software allows us to study the properties of known molecular species as well as “fantasy” species.

            We have recently applied the Winmopac v2.0 software package to the investigation of the energy relationships between various isomers of C₂₀, primarily the ring, bowl, and cage structures.  The significance of C₂₀ is that the bowl structure is a proposed precursor of C₆₀.  Within this hypothesis, two C₂₀ bowl isomers form the caps of the C₆₀ molecule.  Of particular interest, we are studying a proposed reaction mechanism and the corresponding energy profile that describes the evolution of the ring structure to the bowl structure (J. Comput. Chem.  2002, 23(9), 938-942).  For more information regarding this project, click here. We have also investigated and characterized the potential energy surface separating the bowl from the cage isomer.  One of the new isomers discovered during this study possessed a well-defined potential energy well and, of equal importance, a C_2v symmetry that further supports the stability of this isomer (submitted to J. Comput. Chem. October 2002 under revision). 

Currently, our group is studying the potential surface of various small fullerenes.  We continue to study potential surface of the C₂₀ system as we analyze the potential surface separating the ring isomer from the cage.  Information from this aspect of the C₂₀ system, in addition to the information obtained from the other two phases (ring ↔ bowl and bowl ↔ cage) of the project, will then be used to create a schematic of the potential energy surface that contains these three primary isomers.  Our group is also beginning to look beyond the C₂₀ system.  Based on the work reported by Scuseria et. al., we are investigating potential surface in the C₂₈ system, initially studying the energy relationship between the lowest-energy isomers, one a fullerene with icosahedral symmetry and the other a fullerene with D₂ symmetry.  In the future, our investigations of will lead toward understanding the mechanistic and energetic profiles that would describe the transformation between isomers in larger fullerene systems, such as C₂₄, C₂₈, C₃₀, etc.

We are also initiating a projects that will investigate the geometrical and electronic characteristics of ruthenium dyes used in the transfer of radiant light energy into electrical energy and geometric and electronic, as well as their structure-selective relations, of Ru, Pd, and Mo catalysts.

A project whose status is much further down the road into the future is the development of a new methodology to quantify the “heat” of chili peppers.  An interesting method (other than by sense or HPLC) would be to study the FTIR spectra of the capsaicin extracted from numerous peppers and focusing on the intensity of the C=O band, my hypothesis being that the more intense the band, the hotter the pepper.  In addition to extraction techniques, students would also be expected to carry out recrystallization processes, dilution schemes, and sample preparations, properly utilize an FTIR instrument, and evaluate FTIR spectra.