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. Author manuscript; available in PMC: 2012 Jun 6.
Published in final edited form as: Inorg Chem. 2011 May 5;50(11):4811–4824. doi: 10.1021/ic102446n

Table 2.

Effect of homocitrate and imidazole ligand protonation states on the optimized Mo…Fe and Mo-L distances (Å) in the [2FeII-5FeIII-N3−] state. Ocarboxyl(d) and Ocarboxyl(p) represent protonation at the distal and proximal Ocarboxyl center, respectively. The RMS deviations are given relative to the crystal structure.

homocitrate
imidazole		 deprotonated
protonated		 deprotonated
deprotonated		 HOcarboxyl(d)
protonated		 HOcarboxyl(p)
protonated		 HOhydroxyl
protonated		 XRD
Ref. 2 		EXAFS
Ref. 6 		EXAFS
Ref. 72
Mo…Fe(Mo) 2.78 2.80 2.77 2.77 2.74 2.69 2.70 2.68
Mo…S(Mo) 2.40 2.41 2.38 2.38 2.37 2.34 2.37 2.34
Mo-N(His) 2.24 2.17 2.23 2.23 2.21 2.30 2.21a 2.29
Mo-Ocarboxyl 2.10 2.12 2.26 2.24 2.08 2.18 2.21a 2.14
Mo-Ohydroxyl 1.98 1.98 1.99 2.01 2.20 2.20 2.21a 2.31
Avg. Mo-O/N 2.11 2.09 2.16 2.16 2.16 2.22 2.21 2.25
RMS dev. 0.12 0.13 0.11 0.10 0.06
a

Mo-O/N distances were reported only as an average, due to inherent difficulty in distinguishing between light atoms.