Impact of ether coordination on the solid-state luminescence of a lithium β-diketiminate complex.

A solid-state luminescent lithium β-diketiminate complex was synthesized by the reaction of the corresponding proligand and n-butyllithium in hexane. The complex showed a low-coordinated structure in the solution and crystalline states. On the other hand, the lithium complex reacted with diethyl ether, tetrahydrofuran, and 1,4-dioxane to form three-coordinated complexes, which showed lower emission efficiency. Remarkably, the photoluminescence of the crystal of the low-coordinate species was quenched by the treatment with the diethyl ether vapor. NMR spectroscopy and X-ray diffraction analyses revealed that diethyl ether reacts with the complex to afford the three-coordinated ether adduct even in the crystalline state. To the best of our knowledge, this is the first report on the luminescence switching in crystalline materials based on the modification of the coordination number on a lithium atom.