A cubic toluene box with 700 toluene molecules and a side length of 40 Å was generated using packmol. The energy of the box was minimized, it was heated from 0 to 300 K using Langevin dynamics for 300 ps, and then equilibrated at constant temperature and pressure (NPT ensemble) for 400 ps. Since toluene is nonpolar, interactions between CV and the Cl -counterion were expected to be stronger than in methanol. For this reason, CV and Cl -in a contact ion pair configuration were solvated in a 32 Å sphere, containing 588 toluene molecules (see Fig. ), with the toluene positions taken from the equilibrated box configuration. A 48.5 ps QM/MM trajectory was generated, using the same settings as for CV in methanol. The first 12.5 ps were discarded for equilibration of the ion position, yielding 36 ps of usable dynamics (see SI Sec. 4). To probe the effect of the Cl - on the computed dynamics, a single 24 ps trajectory for CV in toluene without a counterion was also produced, following the same computational protocol as outlined for CV in methanol. First, the chromophore was solvated in a toluene sphere of 32 Å, which was pre-heated to 300 K using Langevin thermostat for 300 ps and preequilibrated for 400 ps NPT ensemble. Then the system was equilibrated in the MM regime under open boundary conditions, followed by 26 ps of QM/MM dynamics, where the first 2 ps of the trajectory was discarded to allow for equilibration after switching to the QM/MM Hamiltonian.