Ruthenium d-orbital delocalization in bis(bipyridine)ruthenium derivatives of redox active quinonoid ligands

Abstract Density Functional Theory (DFT) and INDO in the version developed by Zerner (ZINDO) are used to describe how the electronic coupling (π-back-donation etc.) in the series [Ru(bpy) 2 (LL)] 2+ vary as a function of the coordinating atoms of LL. The bidentate ligand LL is o -benzoquinonediimine (NH·NH), and derivatives where one imino group is replaced by oxygen (NH·O) and by sulfur (NH·S). The electronic spectra of these species are calculated using both the INDO/S and time dependent DFRT models and compared with the experimental data. The agreement is excellent. The extent of interaction between the ruthenium dπ orbitals and LL increases in the sequence (NH·NH)