Spectroscopy and Electronic Structures of Ru₂(ap)₄-alkynyl Compounds

A new N,N′-bidentate ligand, 2-(3-isobutoxyanilino)pyridine (HiBuOap), was introduced and used as the ancillary ligand to support highly soluble diruthenium compounds. Thus, the new compounds Ru2(iBuOap)4Cl (1), Ru2(iBuOap)4(CCPh) (2), Ru2(iBuOap)4(CCPh)2 (3), and Ru2(iBuOap)4(CCSiiPr3) (4) were prepared and characterized by both voltammetric and spectroscopic methods, and their physical properties were found to be quite similar to those of the previously reported Ru2(ap)4-based compounds. The spectroscopic properties of both anionic and cationic derivatives of compounds 2 and 3 were examined with spectroelectrochemistry. Density functional theory calculations performed on model compounds of 2 and 3 provide an in-depth picture of the electronic structures of Ru2(ap)4-based alkynyl compounds and assignment of the observed electronic transitions.