Despite their wide use as molecular photoswitches, the mechanistic photophysics of azo dyes are complex and nuanced, and therefore under-explored. To understand the complex electronic interactions that govern the photoisomerization and thermal reversion of two phenyl-azo-indole dyes that differ by R-sterics near the azo bond, potential energy surfaces that combine the dihedral rotation of the azo bond and the aryl inversion on each side of the azo bond were calculated with density functional theory and time-dependent density functional theory. These multidimensional singlet surfaces provide insights into the correlated rotation and inversion pathways allowing for detailed understanding of both photoisomerization, governed by the excited-state surfaces, and thermal reversion, governed by the ground-state surface, mechanisms to be developed. Large plateaus on the S