On the Failure of the Guidry-Drago Reanalysis of Spectroscopic Data for the Reversible Oxygenation of Amine Complexes of Cobalt Protoporphyrin IX Dimethyl Ester

The reanalysis by Guidry and Drago of our spectroscopic data for the reversible oxygenation of amine complexes of cobalt protoporphyrin IX dimethyl ester is examined and shown to lack any redeeming features. A least-squares analysis is presented which supports our earlier analysis and which demonstrates the failure of the various empirical rules devised by Drago and coworkers for the assessment of spectroscopic data. Despite the general success of the least-squares approach used here for the simultaneous determination of the equilibrium constant and the molar absorptivity of the oxygenated species, arguments are presented in favor of our previous procedure of using limiting spectra in the derivation of the equilibrium constant.