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\u27-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. © 2012 American Chemical Society