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

A new N,N'-bidentate ligand, 2-(3-isobutoxyanilino)pyridine (H(i)BuOap), was introduced and used as the ancillary ligand to support highly soluble diruthenium compounds. Thus, the new compounds Ru-2((i)BuOaP)(4)Cl (1), Ru-2 ((i)BuOaP)(4)(C CPh) (2), Ru-2(BuOaP)(4)(C CPh)(2) (3), and Ru-2((i)BuOaP)(4)(C (CSiPr3)-Pr-i) (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 Ru-2(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 Ru-2(ap)(4)-based alkynyl compounds and assignment of the observed electronic transitions.