Table 2.

Experimental and DFT (bold) ⁵⁷Fe hyperfine parameters for 1-OH and 1-F. Experimental parameters were obtained from simulations based on eq 4 using J = 90 cm⁻¹ for both complexes.

	System	δ (mm/s)	ΔEQ (mm/s)	η	D (cm−1)	ax/gnβn (T)	ay/gnβn (T)	az/gnβn (T)	aiso/gnβn (T)
FeIII	1-Fm (DFT)	0.45	1.36	0.9		−21.4	−20.8	−20.5	−20.9a
	1-F (Exp.)	0.45	1.50	4.3	0b	−20.9	−20.9	−20.9	−20.9
	1-OHm (DFT)	0.43	1.24	1.0		−21.4	−20.8	−21.1	−21.1a
	1-OH (Exp.)	0.40	−0.60	5.1	0b	−21.1	−21.1	−21.1	−21.1
FeIV	1-Fm (DFT)	0.14	−0.43	0.7		−18.5	−13.6	−26.1	−19.4a
	1-F (Exp.)	0.10	0.60	−0.7	6.3b	−18.6c	−13.4	−26.3	−19.4
	1-OHm (DFT)	0.13	0.20	0.1		−18.5	−12.2	−23.8	−18.2a
	1-OH (Exp)	0.09	−0.40	10.0	12b	−20.0c	−12.0	−22.5	−18.2

^aThe Fermi contact term is generally poorly reproduced by DFT calculations. We have therefore used the experimental a_iso and added the calculated a_SD to obtain “theoretical” a-values.

^bThe anisotropy of A_a is smaller for 1-F than for 1-OH (see Table 1), implying that the quantity D^e/J is smaller for 1-F. We suspect that D_b has about the same value for the Fe^IV=O sites of both complexes. Note that we arbitrarily set D_a = 0. By using different values for D_a (see eqs 5 and 6) we can achieve the required D^e/J values and use the same D_b for both complexes; it is likely that the two Fe^III sites have a different D_a. For 1-OH we used (E/D)_a = 0 for 1-OH and (E/D = = 0.2 for 1-F.

^cErrors for a-tensor components of the Fe^IV=O sites are roughly ± 2 T.