PHOTODISSOCIATION OF (DMSO)2FE(II)PPIX TO FORM A TRANSIENT 5-COORDINATE COMPLEX AS STUDIED USING TRANSIENT RESONANCE RAMAN-SPECTROSCOPY

Resonance Raman spectra of iron(II) protoporphyrin IX \Fe(II)PP\ in di methyl sulfoxide (DMSO) and deuterated DMSO were obtained at high and low photon densities using 10 ns laser pulses. At low photon density, comparison of the Raman spectra of the complex with those of carbonmon oxy-hemoglobin indicates that a low-spin, six-coordinate (DMSO)2Fe(II) PP complex exists; at high photon density, spectral comparisons with d eoxyhemoglobin and the 2-methylimidazole heme complex (2-MeIm)Fe(II)PP indicate that a transient high-spin, five-coordinate complex is forme d by photodissociation of a DMSO ligand. This phenomenon is reversible and observable on a 10 ns time-scale.