O2-binding to heme: electronic structure and spectrum of oxyheme, studied by multiconfigurational methods
We have studied the ground state of a realistic model of oxyheme with multiconfigurational second-order perturbation theory (CASPT2). Our results show that the ground-state electronic structure is strongly multiconfigurational in character. Thus, the wavefunction is a mixture of many different configurations, of which the three most important ones are approximately 1FeII–1O2 (70%), (12%) and 3FeII