Ground and excited states of oxyheme: SAC/SAC-CI study

✍ Scribed by H. Nakatsuji; J. Hasegawa; H. Ueda; M. Hada

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 499 KB
• Volume: 250
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(96)00033-4

✦ Synopsis

The SAC(symmetrie adapted cluster)/SAC-CI(configuration interaction) mehtod is applied to the ground and low-lying excited states of oxyheme (FeC23N6OzHI6). The ground state (1~) is suitably represented by the Pauling model, Fe(II) (S = 0) + O2(~Ag). The SAC-CI result reproduces well the lower excitation spectrum of oxyhemoglobin. The lowest peak observed at 1.34 eV is assigned to the lag --+ 1~-excitation of the 0 2 ligand. Many transitions originating from the iron d orbitals are calculated, although their intensities are very small. The lowest triplet state (13A~'), which is due to the LAg __+ 3~;g-transition around the 0 2 ligand, is calculated at 0.47 eV above the ground state, but its level is sensitive to the electron correlations included. In the geometry of the deoxy form, this 1 3X' state becomes more stable than the closed-shell singlet state (1~), indicating a geometrical control of oxygen affinity of heine.