Synthesis and Characterization of a Neutral Titanium Tris(iminosemiquinone) Complex Featuring Redox-Active Ligands

The neutral tris­(semiquinonate) complex [Ti­(dmp-BIANisq)3] [dmp-BIANisq = N,N′-bis­(3,5-dimethylphenylimino)­acenaphthenesemiquinonate]
was structurally, spectroscopically, and electrochemically characterized.
Solid-state magnetism experiments reveal field-quenchable, enhanced
temperature-independent paramagnetism (TIP). Density functional theory
calculations employing the experimental geometry predicts a strong
antiferromagnetic coupling, leading to an S = 0 ground
state, but they also hint at spin frustration and concomitant close-lying,
excited states, which cause the observed large TIP by admixture into
the ground state. The dmp-BIANisq ligand, which facilitates
intramolecular electron transfer, was shown to undergo four quasi-reversible
redox processes, demonstrating the ability of the ligand to act as
an electron reservoir in complexes of early metals.