Table 1. Parameters Used for the ENDOR Simulations.

atom (model)	F–Y356•a [Å]	Ax, Ay, Azb [kHz]	aiso [kHz]
Fa (S5)	4.6	580, −1668, −1952	–1013
Fb (S5)	7.3	–246, −246, 492	0
Fc (S2)	8.4	–159, −159, 318	0
Fd (S2)	10.0	–83, −83, 166	0

^aDistances defined with respect to the centroid of Y₃₅₆^•, as shown in Figures 6 and 7B.

^bCoupling constants A_i consider the anisotropic and the isotropic coupling constants (T_i and a_iso, respectively): A_i = T_i + a_iso. Euler angles for relating the A to g tensors are reported in Table S8. An error of ±15 kHz was estimated for couplings <500 kHz, while an error of ±125 kHz is estimated for the 1.6 MHz coupling (ca. 50% of the ENDOR line width parameter in both cases).