Synthesis of Reduced Quinone - Alkali Metal Cation Pairs

Quinone-based molecules are currently being widely studied for use as electrolytes in redox flow batteries. Upon discharge (if used as the positive electrolyte), quinones accept 2 electrons to form a doubly reduced species. In aqueous solutions, this reduced species is typically a hydroquinone, due to the abundance of protons in solution. However, in non-aqueous and/or solvent-free electrolytes, the counterion is not necessarily a proton - it depends on the identity of the negative electrolyte. We aim to synthesize these compounds so that they may be studied directly. We investigate synthesis routes for these reduced quinones paired with alkali metal cations (Na+ and K+), as would be produced in a flow battery with NaK (a eutectic liquid metal) as the negative electrolyte. An ion-exchange procedure based on an existing synthesis route [1], starting from the desired hydroquinone, has been developed to synthesize these compounds. The products of these syntheses have been characterized via 1H NMR and other techniques. References: [1] G. Valulescu, L. Gavrila, S. C. Patrascu, M. N. Vasiliu, D. Jitaru, Rom. 1994, RO 107949 B1 9940131 Figure 1. Generic (oxidized) quinone species (left) discharging to reduced quinone-alkali pair species (right). This can be done with potassium (pictured), lithium, sodium, or another alkali metal ion. Replacing K with H yields a hydroquinone. Xn represent arbitrary side groups. Figure 1