Table 1. OLYP-D3(BJ) Calculated Geometrical, Energetic, and Net Spin Properties of the Optimized DNC Clusters in Fe_a3^HS,3+–OH^––Cu_B, Fe_a3^HS,3+–H₂O···OH^––Cu_B, Fe_a3^HS,3+–OH^–···H₂O–Cu_B, and Fe_a3^HS,3+–H₂O–Cu_B States^a.

	geometry (Å)								net spinf
structureb	Fe–N(H384)	Fe–O	Cu–O	O···O	Fe···Cu	Ec	Qd	pKa(H2O)e	Fea3	O(Fe)/O(Cu)	CuB	Y237
Fea3HS,3+–OH––CuB	2.50	1.99	2.04		3.73	0.0	0		4.08	0.12	–0.39	–0.25
Fea3HS,3+–H2O···OH––CuB	2.18	2.17	1.95	2.50	4.78	6.3	0		4.08	0.08/–0.16	–0.50	0.11
Fea3HS,3+–OH–···H2O–CuB	2.28	1.98	2.13	2.45	4.64	6.6	0		4.12	0.20/–0.03	–0.39	–0.36
Fea3HS,3+–H2O–CuB(a)	2.11	2.39	2.94		4.98	–1.5	1	12.1	4.11	0.04	–0.24	–0.62
Fea3HS,3+–H2O–CuB(b)	2.12	2.47	2.77		4.90	–1.6	1	12.2	4.10	0.04	–0.25	–0.61
Fea3HS,3+–H2O–CuB(c)	2.06	3.55	2.21		4.73	–1.2	1	11.9	4.06	–0.01	–0.36	–0.36
Fea3HS,3+–H2O–CuB(d)	2.09	3.26	2.20		4.73	–0.9	1	11.7	4.09	–0.02	–0.35	–0.44
3S8Gg	2.22	2.39	2.25	1.52	4.92

^aSee Figure 4.

^bGeometries were optimized in the broken-symmetry state with high-spin (HS) Fe_a3³⁺ AF-coupled to the Cu_B site.

^cCalculated broken-symmetry state energies (offset by −26336.6 kcal mol^–1).

^dThe net charge of the model clusters.

^eThe pK_a(H₂O) values were calculated for the process Fe_a3^HS,3+–OH^––Cu_B → Fe_a3^HS,3+–H₂O–Cu_B(a–d).

^fThe Mulliken net spin populations on Fe_a3³⁺, O of the bridging OH^–/H₂O, Cu_B, and the heavy atoms of the Tyr237–O^– side chain (the sum total).

^gThe X-ray crystal structure.³⁷