Figure 8.

DFT geometries and nitrogen hyperfine tensors calculated for different Zn–pyridine distances in P1 (top) and principal values of the hyperfine coupling tensor as a function of the distance between the Zn ion and the nitrogen of the coordinated pyridine molecule obtained from B3LYP/EPRII calculations (bottom). The dashed line indicates the mean Zn–pyridine distance determined on the basis of the known crystal structures.¹⁵ At short Zn–pyridine distances, the ¹⁴N nuclei are inequivalent in pairs, leading to two values for the hyperfine couplings in each direction. The arrows indicate changes in geometry and hyperfine tensors for increasing distances between the Zn ion and the pyridine.