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.

中性三(半醌根)配合物[Ti(dmp-BIANisq)₃]（其中dmp-BIANisq指代N,N′-双(3,5-二甲基苯基亚氨基)苊半醌根）已完成结构、光谱及电化学表征。固态磁性实验结果显示，该配合物存在可被磁场淬灭的增强型温度无关顺磁性（temperature-independent paramagnetism, TIP）。基于实验几何结构开展的密度泛函理论计算预测，体系存在强反铁磁耦合作用，使得基态自旋S=0，但同时也暗示存在自旋阻挫及与之相伴的近简并激发态；这些激发态通过与基态的混合，引发了观测到的显著温度无关顺磁性。此外，能够促进分子内电子转移的dmp-BIANisq配体展现出四组准可逆氧化还原过程，证明了该配体可作为电子储库，在早期过渡金属配合物中发挥功能的能力。