Metal complexes of substituted catecholates and redox flow batteries containing the same
Active materials for flow batteries can include various coordination compounds formed from transition metals. Some compositions containing coordination compounds can include a substituted catecholate ligand having a structure of in a neutral form or a salt form, in which Z is a heteroatom functional group bound to the substituted catecholate ligand at an open aromatic ring position and n is an integer ranging between 1 and 4. When more than one Z is present, each Z can be the same or different. Electrolyte solutions can include such coordination compounds, and such electrolyte solutions can be incorporated within a flow battery.
1. A composition comprising:
a coordination compound that is:
D g M(L 1 )(L 2 )(L 3 )
wherein:
M is a transition metal;
D is NH 4 + , Li + , Na + , or K + ;
g is an integer in a range of between 0 and 6; and
L 1 , L 2 and L 3 are ligands, wherein:
at least one of L 1 , L 2 and L 3 is the substituted catecholate ligand having the structure of:
in a neutral form or a salt form, wherein:
n is an integer in a range of from between 1 and 4,
one or more Z are bound to the substituted catecholate ligand at an open aromatic ring position,
each Z is the same or different when more than one Z is present; and
the 1,2-dihydroxy functionalities on the substituted catecholate ligand are deprotonated and ligated to the transition metal ion;
Z is A 1 R A1 , A 2 R A2 , or A 3 R A3 ;
A 1 is —(CH 2 ) a — or —(CHOR)(CH 2 ) a —;
R A1 is —OR 1 or —(OCH 2 CH 2 O) b R 1 ;
a is an integer in a range of between 0 and about 6, with the proviso that R 1 is not H when a is 0 and R A1 is —OR 1 ;
b is an integer in a range of between 1 and about 10;
R is H, C 1 -C 6 alkyl, heteroatom-substituted C 1 -C 6 alkyl, or C 1 -C 6 carboxyalkyl;
R 1 is H, a C 2 -C 6 polyol bound through an ether linkage, a C 2 -C 6 polyol bound through an ester linkage, or C 1 -C 6 carboxyalkyl;
A 2 is —(CH 2 ) c — or —CH(OR 2 )(CH 2 ) d —;
R A2 is a carbon-linked amino acid or —C(═O)XR 5 ;
X is —O— or —NR 6 —;
c is an integer in a range of between 0 and about 6;
d is an integer in a range of between 0 and about 4;
R 2 and R 6 are, independently, H, C 1 -C 6 alkyl, or heteroatom-substituted C 1 -C 6 alkyl, with the proviso that when Z is A 2 R A2 , A 2 is (CH 2 ) c , and (a) c is 0 and R A2 is C(O)XR 5 , then R 5 is not H or C 1-6 alkyl, (b) and c is 0, then R A2 is not a carbon-linked amino acid;
R 5 is H, C 1 -C 6 alkyl, heteroatom-substituted C 1 -C 6 alkyl, a C 2 -C 6 polyol bound through an ester linkage, a hydroxyacid bound through an ester linkage, a polyglycol acid bound through an ester linkage, an amino alcohol bound through an ester linkage, an amino alcohol bound through an amide linkage, an amino acid bound through an ester linkage, an amino acid bound through an amide linkage, or —(CH 2 CH 2 O) b R 1 ;
A 3 is —O— or —NR 2 —;
R A3 is —(CHR 7 ) e OR 1 , —(CHR 7 ) e C(═O)XR 5 , or —C(═O)(CHR 7 ) f R 8 ;
e is an integer in a range of between 1 and about 6, with the proviso that e is not 1 when A 3 is —O—, and
f is an integer in a range of between 0 and about 6;
R 7 is H or OH;
R 8 is H, C 1 -C 6 alkyl, heteroatom-substituted C 1 -C 6 alkyl, a C 2 -C 6 polyol bound through an ether linkage, a C 2 -C 6 polyol bound through an ester linkage, a hydroxyacid bound through an ether linkage, a hydroxyacid bound through an ester linkage, a polyglycol acid bound through an ether linkage or an ester linkage, an amino alcohol bound through an ether linkage, an amino alcohol bound through an ester linkage, an amino alcohol bound through an amide linkage, an amino acid bound through an ether linkage, an amino acid bound through an ester linkage, an amino acid bound through an amide linkage, a carbon-linked amino acid, or —(OCH 2 CH 2 O) b R 1 ; and wherein:
(a) L 1 and L 2 are substituted catecholate ligands and L 3 is an unsubstituted catecholate ligand; or
(b) L 1 is the substituted catecholate ligand and L 2 and L 3 are unsubstituted catecholate ligands; or
(c) any L 1 , L 2 and L 3 that is not a substituted catecholate ligand comprises, independently, an unsubstituted catecholate, ascorbate, citrate, glycolate, polyol, gluconate, hydroxyalkanoate, acetate, formate, benzoate, malate, maleate, phthalate, sarcosinate, salicylate, oxalate, urea, polyamine, aminophenolate, acetylacetonate, or lactate; or
(d) all of L 1 , L 2 and L 3 are substituted catecholate ligands having the structure of:
2. The composition of claim 1 , wherein at least two of L 1 , L 2 and L 3 are substituted catecholate ligands.
3. The composition of claim 1 , wherein the transition metal is Ti.
4. The composition of claim 1 , wherein the substituted catecholate ligand is:
5. The composition of claim 1 , wherein the substituted catecholate ligand has a structure that is:
or a stereoisomer thereof.
6. The composition of claim 1 , wherein the substituted catecholate ligand is:
7. An electrolyte solution comprising the composition of claim 1 , wherein:
the electrolyte solution is an aqueous solution, and
the aqueous solution has a pH in range of between about 1 and about 13.
8. The electrolyte solution of claim 7 , wherein the transition metal is Ti.
9. The electrolyte solution of claim 7 , wherein a concentration of the coordination compound in the aqueous solution ranges between about 0.5 M and about 3 M.
10. A flow battery comprising an electrolyte solution comprising the composition of claim 1 .
11. The flow battery of claim 10 , wherein the transition metal is Ti.
12. The composition according to claim 1 , wherein Z 1 is A l R A1 .
13. The composition according to claim 12 , wherein A 1 is —(CH 2 ) a —.
14. The composition according to claim 12 , wherein A 1 is —(CHOR)(CH 2 ) a —.
15. The composition according to claim 12 , wherein R A1 is —OR 1 .
16. The composition according to claim 12 , wherein R A1 is —(OCH 2 CH 2 O) b R 1 .
17. The composition according to claim 1 , wherein Z 1 is A 2 R A2 .
18. The composition according to claim 17 , wherein A 2 is —(CH 2 ) c —.
19. The composition according to claim 17 , wherein A 2 is —CH(OR 2 )(CH 2 ) d —.
20. The composition according to claim 17 , wherein R A2 is a carbon-linked amino acid.
21. The composition according to claim 17 , wherein R A2 is —C(═O)XR 5 .
22. The composition according to claim 21 , wherein X is —O—.
23. The composition according to claim 21 , wherein X is —NR 6 —.
24. The composition according to claim 1 , wherein Z 1 is A 3 R A3 .
25. The composition according to claim 24 , wherein A 3 is —O—.
26. The composition according to claim 24 , wherein A 3 is —NR 2 —.
27. The composition according to claim 24 , wherein R A3 is —(CHR 7 ) e OR 1 .
28. The composition according to claim 24 , wherein R A3 is —(CHR 7 ) e C(═O)XR 5 .
29. The composition according to claim 24 , wherein R A3 is —C(═O)(CHR 7 ) f R 8 .