The synthetic chemistry of substituted 4,4′-azobis(phenylcyanamide) ligands was investigated, and the complexes [{Ru(tpy)(bpy)}<inf>2</inf>( μ-L)][PF<inf>6</inf>]<inf>2</inf>, where L = 2,2′:5,5′-tetramethyl-4,4′-azobis(phenylcyanamido) (Me<inf>4</inf>adpc<sup>2-</sup>), 2,2′-dimethyl-4,4′-azobis(phenylcyanamido) (Me<inf>2</inf>adpc<sup>2-</sup>), unsubstituted (adpc<sup>2-</sup>), 3,3′-dichloro-4,4′-azobis(phenylcyanamido) (Cl<inf>2</inf>adpc<sup>2-</sup>), and 2,2′:5,5′-tetrachloro-4,4′-azobis(phenylcyanamido) (Cl<inf>4</inf>adpc<sup>2-</sup>), were prepared and characterized by cyclic voltammetry and vis-near-IR (NIR) and IR spectroelectrochemistry. The room temperature electron paramagnetic resonance spectrum of [{Ru(tpy)(bpy)}<inf>2</inf>( μ-Me<inf>4</inf>adpc)]<sup>3+</sup> showed an organic radical signal and is consistent with an oxidation-state description [Ru<sup>II</sup>, Me<inf>4</inf>adpc<sup>•-</sup>, Ru<sup>II</sup>]<sup>3+</sup>, while that of [{Ru(tpy)(bpy)}<inf>2</inf>( μ-Cl<inf>2</inf>adpc)]<sup>3+</sup> at 10 K showed a low-symmetry Ru<sup>III</sup> signal, which is consistent with the description [Ru<sup>III</sup>, Cl<inf>2</inf>adpc<sup>2-</sup>, Ru<sup>II</sup>]<sup>3+</sup>. IR spectroelectrochemistry data suggest that [{Ru(tpy)(bpy)}<inf>2</inf>( μ-adpc)]<sup>3+</sup> is delocalized and [{Ru(tpy)(bpy)}<inf>2</inf>( μ-Cl<inf>2</inf>adpc)]<sup>3+</sup> and [{Ru(tpy)(bpy)}<inf>2</inf>( μ-Cl<inf>4</inf>adpc)]<sup>3+</sup> are valence-trapped mixed-valence systems. A NIR absorption band that is unique to all [{Ru(tpy)(bpy)}<inf>2</inf>( μ-L)]<sup>3+</sup> complexes is observed; however, its energy and intensity vary depending on the nature of the bridging ligand and, hence, the complexes oxidation-state description.

Additional Metadata
Persistent URL dx.doi.org/10.1021/ic502487x
Journal Inorganic Chemistry
Citation
Choudhuri, M.M.R. (Mohommad M. R.), Behzad, M. (Mahdi), Al-Noaimi, M. (Mousa), Yap, G.P.A. (Glenn P. A.), Kaim, W. (Wolfgang), Sarkar, B. (Biprajit), & Crutchley, R. (2015). Variable noninnocence of substituted azobis(phenylcyanamido)diruthenium complexes. Inorganic Chemistry, 54(4), 1508–1517. doi:10.1021/ic502487x