A quantum chemical investigation of the photodissociation of the nitrosyl hematoporphyrin complex.

The photodissociation process of the nitrosyl hematoporphyrin complex has been studied using quantum-chemical methods. Photolysis of hematoporphyrin complexes is of high biological usefulness and is widely employed in laser-therapy methods. However, the mechanism of photodissociation of these complexes is not entirely clear. Based on the computations, we propose a detailed mechanism for the photolysis of the nitrosyl hematoporphyrin complex. A transition 'dissociative' excited state has been described, which has an energy barrier value of only 0.4 eV for NO dissociation. [ABSTRACT FROM AUTHOR]