| Abstract: | Carbonyl stretching frequencies of acyl groups conjugated with porphyrin rings are useful probes of the effective electronegativities of corrdinated iron atoms in iron porphyrins. Acetyl carbonyl stretching frequencies for 2,4-diacetyldeuteroporphyrin IX dimethyl ester derivatives exhibit both metal oxidation state and axial ligand effects. Infrared spectra of chloroform and pyridine solutions, corrected for solvation, showed the sequences of acetyl carbonyl stretching frequencies: dipyridine iron(II) less than mu-oxo bisiron(III) less than bromo iron(III) approximately equal to chloro iron(III) and dipyridine nickel(II) less than nickel(II). Applications of the probe to the study of hemeproteins are indicated. |
