relative concentration to the S = 3/2 species. In order to understand this difference, we used the ORCA quantum chemistry program in conjunction with a published isomer shift correlation to calculate the Mössbauer parameters of 8, 9, and 10 using DFT at the B3LYP/ZORA-def2-TZVP level of theory. All initial Mössbauer computations were carried out on BP86-optimized structures from X-ray diffraction data in the quartet spin state in accordance with experimental evidence. No counterions were included for anionic 9 and 10, as previous studies have indicated that Mössbauer predictions are largely independent of the counterion. These potassium-free calculated parameters were in agreement with the experimental Mössbauer parameters of thiolate complex 8 and ammonia complex 10, but both δ and |ΔEQ| of amide complex 9 were overestimated by 0.11 mm/s and 3.18 mm/s, respectively (Table ). Since the crystal structure of 9 shows a potassium cation only 3.13 Å from one S atom in the SCS pincer, we hypothesized that including K + may be necessary to properly describe its electronic structure. Thus, we started from the crystallographic structure of 9 and performed Mössbauer calculations on structures that included K + : one with geometry optimization of all atoms (model A) and one with only H atoms optimized (model B) (Figure ). Model C in Figure is the optimized structure of potassium-free 9, whose predicted Mössbauer parameters are listed in Table . In the crystal structure, the potassium is also coordinated to a Dipp aryl group of a neighboring molecule of 9, and this second arene was modeled as benzene in the calculations.