Iron(II) and ruthenium(II) complexes with polypyridine derivatives as sensitizers for DSSC: the structure and spectral properties,as studied by quantum chemistry methods

Density functional calculations of the geometries, electronic structures, and spectral properties of a series of iron(II) and ruthenium(II) complexes with 4,4´,4´,4´´-substituted 2,2´:6´2´´:6´´,2´´´-quaterpyridines were carried out. A high-spin state is characteristic of the iron(II) complexes with Cl^–, NO^–, CNS^–, and I^– as axial ligands while a low-spin state is characteristic of the iron(II) complex with a CN^– axial ligand. Calculations of the complexes with the nitroxide ligand predict intense absorption in a wide wavelength range up to the IR region.