EPR spectra of frozen solutions of
[Fe(AH1−H)(AH1−2H)] (200
μM) in DMSO/water (70/30% v/v) at various pH values. The spectra
corresponding to three distinct low-spin Fe(III) species are indicated as
complexes I, II, and III. The spectra of mixtures are shown in grey.
Experimental conditions: mw frequency, 9.444 GHz; mw power, 2 mW; magnetic field
modulation amplitude, 0.2 mT; temperature, 77 K.