Semiempirical configuration interaction calculations for ru‐centered dyes*

Computational investigation of the photochemical properties of transition‐metal‐centered dyes typically involves optimization of the molecular structure followed by calculation of the UV/visible spectrum. At present, these steps are usually carried out using density functional theory (DFT) and time‐dependent DFT calculations. Recently, we demonstrated that semiempirical methods with appropriate parameterization could yield geometries that were in very good agreement with DFT calculations, allowing large sets of molecules to be screened quickly and efficiently. In this article, we modify a configuration interaction (CI) method based on a semiempirical PM6 Hamiltonian to determine the UV/visible absorption spectra of Ru‐centered complexes. Our modification to the CI method is based on a scaling of the two‐center, two‐electron Coulomb integrals. This modified, PM6‐based method shows a significantly better match to the experimental absorption spectra versus the default configuration interaction method (in MOPAC) on a training set of 13 molecules. In particular, the modified PM6 method blue‐shifts the location of the metal‐to‐ligand charge‐transfer (MLCT) peaks, in better agreement with experimental and DFT‐based computational results, correcting a significant deficiency of the unmodified method. Published 2018. This article is a U.S. Government work and is in the public domain in the USA