EPR STUDIES OF WEAKLY COUPLED OXOMOLYBDENUM(V) AND LOW-SPIN IRON(III)PORPHYRIN CENTERS

Novel compounds containing two S=1/2 coupled spin centers (Mo(V) and l ow spin Fe(III)) have been investigated in detail by X- and Q-band EPR spectroscopy, spectral simulation and molecular modelling calculation s. For one system with a Mo-Fe distance of similar to 9.4 Angstrom the dominant dipolar coupling allows distinction among structures that ar e consistent with molecular modelling calculations. For the second sys tem with a Mo-Fe of similar to 7.9 Angstrom the exchange interaction i s dominant (0.5 < J < 3.0 GHz). These coupled systems are preliminary benchmarks for using EPR to investigate the Mo-Fe interaction in sulfi te oxidase.