Influence of heme periphery on the electronic structure and Mössbauer parameters of hemoglobin

For the five-coordinated complexes of ferroprotoporphynynn with imidazole, a quantum-chemical analysis of the electronic structure and Mossbauer spectral parameters has been canied out. Peripheral substituents (―CH3, ―Cf13, ―C2H4COOH) were introduced into the porphynin macrocycle to model the real chemical structure of protopo'phynynn in the heme group of desoxyhemoglobin. The calculations have shown that near the occupation border in the complaes there are MO which are due to the π-systems of the ―CH= CM2 and ―CH2―CH2COOH substituents. The orientalion of the vinyl fragments has a considerable effect on the populations of the Fe d-orbitals and the quadrupole splitting ΔEQ for the5B1 and5B2 terns.