The electronic structure method is undoubtedly one source of potential error for the missing spectral width for NR in DMSO. When we examined the effect of the TDA versus the full solution of the TDDFT equations on five snapshots, we found that the second vibronic peak gains significant intensity in both absorption and emission spectra (see Figure ), which would lead to a considerable broadening of the simulated absorption and emission spectra if the TDDFT lineshape was used instead of the TDA lineshape. Additionally, benchmarking FTFC lineshapes against two other density functionals showed that although the M06-2X method gives good agreement with the CAM-B3LYP lineshapes, the LC-ωHPBE functional produces FTFC spectra that are substantially broader than the other two functionals (Figure ). Thus, by changing the electronic structure method to one with broader vibronic spectra, we can expect improved agreement with the experimental absorption spectrum; however, the emission spectrum would also gain additional broadening and become broader than the experimental spectrum. Overall, the vibronic broadening appears underestimated with TDA-CAM-B3LYP for Nile Red in DMSO. This underestimated vibronic broadening may also be responsible for the underestimated Stokes shifts, as the increased intensity of the second vibronic peak may change the position of the spectral maxima and increase the energy between the maxima of the absorp- C. 7MC in Methanol 7-Methoxycoumarin-4-acetic acid (7MC), like NBD, is a push-pull electron system and is used as a fluorescent probe in various cell biology applications. 121,122,141 7MC shows the largest conformational changes and the largest number of hydrogen bonds of all three dyes studied here. Due to the carboxylic acid group and the carbonyl bond, 7MC acts as both an acceptor and donor of hydrogen bonds in methanol. The experimental FWHM values are 0.563 and 0.539 eV for absorption and emission lineshapes, indicating similar potential energy surfaces for ground and excited states with a Stokes shift of 0.683 eV, the largest among all three dyes studied here.