Session: Undergraduate Research Posters: Computational Chemistry:

Azoheteroarenes are relatively new photoswitchable compounds, with one of the aryl rings of an azobenzene molecule replaced by a heteroaromatic five-membered ring. The thermal stability of molecular switches is one of the primary factors considered in the design process. For the purposes of quick information transmission in materials science, the thermal (Z – E) relaxation process should be as short as possible. On the other hand, molecular memory storage devices prefer long Z – E relaxation times. In this work, it was examined how oriented external electric fields (OEEFs) can be used to tune the photoswitching properties of three unsubstituted heteroaryl azo compounds — azoimidazole (im), azopyrazole (pz), and azopyrrole (py). Based on a density functional theory approach, the electric field control of the thermal relaxation time and nonlinear optical properties of im, pz, and py was examined. Wiberg indices and the natural bond orbital analysis were found to explain the correlation between the calculated thermal half-lives and the OEEF effects on the length of the Z – E isomerization. Molecules with higher Wiberg indices offered longer thermal half-lives at the expense of higher activation energy barriers. However, favorable OEEF orientations were found to change thermal half-lives by as much as 300 days.

Lee M Thompson

University of Louisville

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