By Sean McGavin, Alex Bindon

Faculty Mentor:  Dr. Leanna Giancarlo

Abstract

The effect of a conjugated chain’s length on the absorption peaks in ultraviolet-visible (UV-Vis) spectra has been quantified, wherein increasing the chain’s length increases the absorption wavelength of the peak. However, how the peaks are shifted due to the presence of multiple isolated conjugated chains is not established. This study utilized the computational chemistry software, GAMESS, to analyze various molecules each possessing isolated conjugated chains. The variables tested were the number of conjugated chains within a molecule, the length of one chain compared to the other, and the number of bonds between the chains. The intensity of peaks and wavelength within the calculated spectra were then compared to determine the trend of the changed variables. In molecules with multiple conjugated chains of unequal length, the chains possess their own independent peaks in the UV-Vis spectrum. In molecules that contained equal length chains, a single peak is present with amplified intensity, due to constructive inference. By increasing the distance between the isolated conjugated chains, the peaks become sharper as it is increasingly difficult for the electrons to jump from one isolated chain to the next. Isolated conjugated chains had a significant effect on the wavelength of absorption. Using the trends outlined in this study, a more thorough investigation can be undertaken where these effects are quantified.