High-solubility thioether quinones
Substituted hydroquinones and quinones and methods of synthesizing such compounds are disclosed herein. The substituted hydroquinones have the formula: while the substituted quinones have the corresponding oxidized structure (1,4-benzoquinones). One, two, three, or all four of R 1 , R 2 , R 3 and R 4 comprise a thioether moiety and a sulfonate moiety, and wherein each R 1 , R 2 , R 3 and R 4 that does not comprise a thioether and a sulfonate moiety sulfonate moiety is independently a hydrogen, an alkyl or an electron withdrawing group. The substituted hydroquinones and quinones are soluble in water, stable in aqueous acid solutions, and have a high reduction potential in the oxidized form. Accordingly, they can be used as redox mediators in emerging technologies, such as in mediated fuel cells or organic-mediator flow batteries.
1. A substituted hydroquinone having the formula:
wherein one, two, three, or all four of R 1 , R 2 , R 3 and R 4 comprise a thioether moiety and a sulfonate moiety, and wherein each R 1 , R 2 , R 3 and R 4 that does not comprise a thioether and a sulfonate moiety is independently a hydrogen, an alkyl, or an electron withdrawing group; or
the oxidized form (the substituted 1,4-benzoquinone form) of said substituted hydroquinone.
2. The substituted hydroquinone or benzoquinone of claim 1 , wherein each of the one, two, three, or four of R 1 , R 2 , R 3 and R 4 that comprise a thioether moiety and a sulfonate moiety independently has the chemical structure S(CH 2 ) n SO 3 − , wherein n is 1, 2, 3 or 4.
3. The substituted hydroquinone or benzoquinone of claim 1 , wherein one of R 1 , R 2 , R 3 and R 4 comprises a thioether moiety and a sulfonate moiety, and wherein the R 1 , R 2 , R 3 and R 4 that do not comprise a thioether and a sulfonate moiety are independently a hydrogen, an electron withdrawing group, or an alkyl.
4. The substituted hydroquinone or benzoquinone of claim 1 , wherein three or all four of R 1 , R 2 , R 3 and R 4 comprise a thioether moiety and a sulfonate moiety.
5. The substituted hydroquinone or benzoquinone of claim 4 , wherein three of R 1 , R 2 , R 3 and R 4 comprise a thioether moiety and a sulfonate moiety, and wherein the R 1 , R 2 , R 3 and R 4 that does not comprise a thioether and a sulfonate moiety is an electron withdrawing group or an alkyl.
6. The substituted hydroquinone or benzoquinone of claim 1 , wherein the electron withdrawing group is selected from the group consisting of nitrile (cyanide), an amide, a ketone, —CF 3 , —SF 5 , an imide, an imidazole, a benzimidazole, an oxazole, a benzoxazole, a thiazole, a benzthiazole, and a pyrazole.
7. The substituted hydroquinone or benzoquinone of claim 4 , wherein all four of R 1 , R 2 , R 3 and R 4 comprise a thioether moiety and a sulfonate moiety.
8. The substituted hydroquinone or benzoquinone of claim 1 , wherein the hydroquinone form is selected from the group consisting of:
wherein X is a hydrogen, an electron withdrawing group, or an alkyl; and
wherein X is a hydrogen, an electron withdrawing group, or an alkyl.
9. The substituted hydroquinone or benzoquinone of claim 8 , wherein the electron withdrawing group is selected from the group consisting of nitrile (cyanide), an amide, a ketone, —CF 3 , —SF 5 , an imide, an imidazole, a benzimidazole, an oxazole, a benzoxazole, a thiazole, a benzthiazole, and a pyrazole.
10. The substituted hydroquinone or benzoquinone of claim 1 , wherein the hydroquinone form is selected from the group consisting of:
wherein X is a hydrogen, an electron withdrawing group, or an alkyl; and
wherein X is a hydrogen, an electron withdrawing group, or an alkyl.
11. The substituted hydroquinone or benzoquinone of claim 10 , wherein the electron withdrawing group is selected from the group consisting of nitrile (cyanide), an amide, a ketone, —CF 3 , —SF 5 , an imide, an imidazole, a benzimidazole, an oxazole, a benzoxazole, a thiazole, a benzthiazole, and a pyrazole.
12. The substituted hydroquinone or benzoquinone of claim 10 , wherein X is methyl.