To determine which solvent interactions contributed to this vibronic broadening, we then calculated the Franck-Condon spectrum for only the closest four axial solvent molecules as QM or only the four peripheral Hbonding solvent molecules as QM, with all remaining solvent treated as MM. The QM treatment of the axial solvent led to minimal change in the spectrum, see the blue dotted line in Figure . In contrast, the QM treatment of the four peripheral H-bonding solvent molecules (blue dashed line) led to significant additional vibronic broadening, with the spectrum nearing the result for the QM solvation shell treatment (blue solid line). Analyzing the average peripheral H-bond distance between the solvent and the amine of CV + from the optimized structures shows that the H-bond distance increases by 0.12-0.26 Å going from MM to QM treatment of these solvent molecules, see SI section S10. To better understand this change in distance, we revisit the potential energy scan for a peripheral H-bond, where the methanol molecule was treated as QM, see blue line in Figure (top), and recall that the minimum in the potential of the H-bonding methanol is at a larger distance for QM treatment compared to MM treatment, in agreement with the change in distance for the optimized geometry.