All transition structure calculations were performed in Gaussian 16 with the PBE0/6-31+G(d,p) method and the IEFPCM water solvation model, which we found to have an optimal balance of accuracy and computational cost. Next, we performed intrinsic reaction coordinate (IRC) calculations and optimized the reactive conformers corresponding to the E and Z isomers for a given thermal isomerization. The reactive Zisomers were used to calculate the thermal barrier. For our set of 26 photoswitches, we confirmed that 17 underwent an inversion mechanism, while the remaining 9 underwent rotation. All systems that underwent a rotation mechanism were substituted with OMe groups on the thiophene ring, while all photoswitches with unsubstituted thiophene rings underwent an inversion mechanism. Four dimethoxy substituted systems underwent inversion: 1-OMe (no substituent on the phenyl ring), 2-OMe (OMe substituted phenyl), 3-OMe (NH 2 substituted phenyl), and 4-OMe (vinyl diene substituent with a methoxy terminus). All transition state geometries are given in the supporting information (SI).