Analogously, we performed Mössbauer calculations on all-atom-optimized 9-crown with potassium included. This structure gave δ = 0.16 mm/s and ΔEQ = -0.91 mm/s, in agreement with experimental values for 9-crown despite the potassium being formally outer sphere with an Fe•••K distance of 8.026 Å. The Löwdin charge on potassium was found to be -0.06 in this structure, suggesting significant delocalization of positive charge onto the coordinated THF and crown ether components. To test the isolated effect of a distant and free potassium ion, we removed the two THF molecules and the 18-crown-6 that were coordinated to potassium in optimized 9-crown and repeated the Mössbauer calculations (Figure ). This model gave δ = 0.33 mm/s and ΔEQ = -4.08 mm/s, which is not close to the experimental spectrum of 9-crown and instead is much closer to that calculated for model C (anionic 9). In contrast to the structure containing THF and 18-crown-6, the Löwdin charge on potassium was found to be +0.99 in this structure. These results indicate that the THF and 18-crown-6 may be accepting most of the positive charge of the potassium cation, which then places enough positive charge close to the iron to alter its electronic structure. Charge reorganization, albeit in varying degrees, has been implicated as a stabilizing factor in the formation of alkali-crown complexes in previous theoretical studies. Additionally, although the anionic model of thiolate complex 8 was in agreement with experiment, we calculated Mössbauer parameters for optimized 8-crown with potassium included to evaluate its consistency with experiment. This calculation gave δ = 0.28 mm/s and ΔEQ = 3.96 mm/s, also in agreement with the spectrum of 8-crown and essentially unchanged from the potassium-free predictions for 8 that are shown in Table . Taken together, the experimental and computed Mössbauer spectra for the models described above suggest that the amide donor in 9 leads to an unusual situation in which its electronic structure is dependent on the presence of a nearby cation.