Noninnocence Driven Superexchange Within a Ti²⁺/Ti⁴⁺ Mixed Valence Complex

An example of a molecular Ti²⁺/Ti⁴⁺ complex is reported, whereby the metal centers are bridged by the redox-active tetrakis(imino)pyracene ligand (TIP). Spectroscopic, electrochemical, electronic structure calculations, and magnetic analyses were used to evaluate the degree and mechanism of electronic communication and magnetic exchange between the two metal centers. It was found that the complex is best described as a borderline Class II/III mixed valence complex, whereby the population of thermally accessible, close-lying excited states gives rise to extremely strong antiferromagnetic coupling (|J|> 250 cm^-1 at ∼11.3 Å).