For complexes include spin-orbit coupling (SOC), open shell states and degeneracy, a higher level method is desired. One such class of methods is muti-congurational self consistent field (MCSCF), among which the most widely adopt method is restricted active space self consistent field (RASSCF), choosing most important orbitals in active space, not only the metal character 3d molecular orbitals (MOs), but also the important ligand MOs. In our calculation, the metal character 3d orbital and orbitals strongly correlate with them, such as the bonding and anti-bonding partners, are all included in RAS2. To model X-rays, important spectral effects such as multiplet effects, SOC and charge transfer features have to be described accurately. All the calculations can be performed with MOLCAS 8.1 or OpenMOLCAS.
For this project, the target complexes would be earth abundant iron based carbene photosensitizers, the different X-ray spectroscopy have been measured by researchers in the current group. In order to understand how the different character ligand tune the property such as the lifetime of charge-transfer states. Better understanding of the electronic structures is required, the forementioned RAS method has been extended and applied to simulate and interpret different X-rays successfully, and we will combine the experimental and theoretical effort to understand the spin or electron redistribution or delocalisation along the oxidation or spin state change, which we believe that will guide better phtosensitizer design.