Table 5.

Core structural parameters in doubly and triply bridged diiron(II,III) cores in proteins and in model complexes.

	r(Fe···Fe) (Å)	∠Fe-μ-O-Fe (°)	Ref
Doubly bridged diiron centers
1	3.603†	128.0†	*
2	3.632	129.3	*
Mouse MIOX·MI #	3.65	130	32
Human MIOX·MI #	3.72	124	33
Triply bridged diiron centers
[FeIIFeIII(Me3-TACN)(OH) (O2CiPr)2]2+	3.400	118.1	45
[FeIIFeIII(BPMP)(O2CCH2CH3)2]2+	3.365	113.1	39
[FeIIFeIII(tpdb)(O2CPh)2]2+	3.300	105.8	47
Diiron(II,III) form of DcrH	3.34	115.1	70
Pig uterroferrin #	3.31	105.7	69

^*This work.

^# The crystal structure may represent a diiron(III,III) form or a diiron(II,III) state.

Abbreviations used: MIOX = myo-inositol oxygenase; MI = myo-inositol. Me₃-TACN = 1,4,7-trimethyl-1,4,7-triazacyclononane; BPMP = 2,6-bis[(bis(2-pyridylmethyl)-amino)methyl]-4-methylphenolate; tpdb = N,N,N′,N′-tetrakis(2-pyridyl-methyl)-1,4-diaminobutane-2-olate. DcrH = a bacterial chemotaxis protein from Desulfovibrio vulgaris with a Hr-like domain.

^†DFT values: Fe···Fe = 3.701 Å (3.703 Å) and ∠Fe-OFe = 127.9° (127.4°) for broken symmetry state (ferromagnetic state).