Carbon Monoxide Coordination by Iron(II) meso-Mono-4-Pyridyltriphenylporphyrinate (FeM4PyTPP) and Its Structure in Sublimed Layers

Interaction of CO with sublimed layers of iron(II) meso-mono-4-pyridyltriphenylporphyrinate (FeM4PyTPP) resulting in the formation of known mono- and dicarbonyl complexes was studied using IR spectroscopy. The frequency of the stretching vibration of the coordinated CO in the monocarbonyl complex was found to be ∼20 cm–1higher than in the complex with iron meso-tetraphenylporphyrinate (FeTPP), with the former complex being significantly more stable than the latter. The differences observed in CO coordination by porphyrins with close structures are explained by the formation, in the FeM4PyTPP sublimed layers, of oligomeric structures where the pyridyl group of one molecule is coordinated by the metal ion of the neighboring molecule. This conclusion is confirmed by a comparative analysis of IR spectra of FeM4PyTPP and FeTPP in the regions of structurally sensitive vibrations.