Transition metal complexes with bidentate ligand having an imidazole ring
Novel transition metal complexes of iron, cobalt, ruthenium, osmium, and vanadium are described. The transition metal complexes can be used as redox mediators in enzyme based electrochemical sensors. In such instances, transition metal complexes accept electrons from, or transfer electrons to, enzymes at a high rate and also exchange electrons rapidly with the sensor. The transition metal complexes include at least one substituted or unsubstituted biimidazole ligand and may further include a second substituted or unsubstituted biimidazole ligand or a substituted or unsubstituted bipyridine or pyridylimidazole ligand. Transition metal complexes attached to polymeric backbones are also described.
1. A redox mediator having the formula:
wherein M is iron, cobalt, ruthenium, osmium, or vanadium;
L is a bidentate ligand comprising at least one imidazole ring;
c is an integer selected from −1 to −5 or +1 to +5 indicating a positive or negative charge;
X represents at least one counter ion;
d is an integer from 1 to 5 representing the number of counter ions, X; and
L 1 , L 2 , L 3 and L 4 are ligands,
wherein L 1 and L 2 form a second bidentate ligand and wherein the second bidentate ligand comprises at least one substituted or unsubstituted heterocyclic nitrogen-containing-ring and wherein at least one of L, L 1 , L 2 , L 3 and L 4 is coupled to a polymeric backbone.
2. The redox mediator of claim 1 , wherein L is
wherein R 1 and R 2 are independently —H or substituted or unsubstituted alkyl, alkenyl, or aryl; and
R 3 , R 4 , R 5 , and R 6 are independently —H, —F, —Cl, —Br, —I, —NO 2 , —CN, —CO 2 H, —SO 3 H, —NHNH 2 , —SH, —OH, —NH 2 , or substituted or unsubstituted alkoxylcarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, alkoxy, alkylamino, dialkylamino, alkanoylamino, arylcarboxamido, hydrazino, alkylhydrazino, hydroxylamino, alkoxylamino, alkylthio, alkenyl, aryl, or alkyl.
3. The redox mediator of claim 2 , wherein R 1 and R 2 are unsubstituted C1 to C12 alkyl.
4. The redox mediator of claim 2 , wherein R 3 , R 4 , R 5 and R 6 are —H.
5. The redox mediator of claim 1 , wherein L 1 comprises a heterocyclic compound containing at least one nitrogen atom.
6. The redox mediator of claim 1 , wherein L 1 comprises a heterocyclic compound coupled to the polymeric backbone.
7. The redox mediator of claim 1 , wherein the second bidentate ligand comprises a 2,2′-bipyridine having the following formula:
wherein R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 and R 23 are independently —H, —F, —Cl, —Br, —I, —NO 2 , —CN, —CO 2 H, —SO 3 H, —NHNH 2 , —SH, —OH, —NH 2 , or substituted or unsubstituted alkoxylcarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, alkoxy, alkylamino, dialkylamino, alkanoylamino, arylcarboxamido, hydrazino, alkylhydrazino, hydroxylamino, alkoxylamino, alkylthio, alkenyl, aryl, or alkyl.
8. The redox mediator of claim 1 , wherein L 3 and L 4 in combination form a third bidentate ligand.
9. The redox mediator of claim 8 , wherein at least one of the second and third bidentate ligands is a substituted or unsubstituted 2,2′-bipyridine, a substituted or unsubstituted 2,2′-biimidazole, or a substituted or unsubstituted 2-(2-pyridyl)imidazole.
10. The redox mediator of claim 8 , wherein M is osmium and the transition complex has the following formula:
wherein R 3 , R 4 , R 5 , R 6 , R 16 , R 17 , R 19 , R 20 , R 22 and R 23 are —H;
R 18 and R 21 are independently substituted or unsubstituted C1 to C12 alkyls; and
R 18 and R 21 are independently —H or substituted or unsubstituted C1-C12 alkoxy, C1-12 alkylthio, C1-C12 alkylamino, C2-C24 dialkylamino, or C1-C12 alkyl.
11. The redox mediator of claim 10 , wherein at least one of R 1 , R 2 , R 18 and R 21 comprises a reactive group, wherein the reactive group is a carboxy, an activated ester, a sulfonyl halide, a sulfonate ester, an isocyanate, an isothiocyanate, an epoxide, an aziridine, a halide, an aldehyde, a ketone, an amine, an acrylamide, a thiol, an acyl azide, an acyl halide, a hydrazine, a hydroxylamine, an alkyl halide, an imidazole, a pyridine, a phenol, an alkyl sulfonate, a halotriazine, an imido ester, a maleimide, a hydrazide, a hydroxy, or a photo-reactive azido aryl group.
12. The redox mediator of claim 10 , wherein at least one of R 1 , R 2 , R 18 , and R 21 is coupled to a polymeric backbone.
13. The redox mediator of claim 8 , wherein M is osmium and the transition complex has the following formula:
wherein R 3 , R 4 , R 5 , R 6 , R′ 3 , R′ 4 , R a , and R c are —H; R d is —H or methyl; R b is —H or substituted or unsubstituted C1-C12 alkoxy, C1-12 alkylthio, C1-C12 alkylamino, C2-C24 dialkylamino, or C1-C12 alkyl; and R 1 , R′ 1 and R 2 are independently substituted or unsubstituted C1 to C12 alkyl.
14. The redox mediator of claim 13 , wherein at least one of R 1 , R 2 , and R′ 1 comprises a reactive group, wherein the reactive group is a carboxy, an activated ester, a sulfonyl halide, a sulfonate ester, an isocyanate, an isothiocyanate, an epoxide, an aziridine, a halide, an aldehyde, a ketone, an amine, an acrylamide, a thiol, an acyl azide, an acyl halide, a hydrazine, a hydroxylamine, an alkyl halide, an imidazole, a pyridine, a phenol, an alkyl sulfonate, a halotriazine, an imido ester, a maleimide, a hydrazide, a hydroxy, or a photo-reactive azido aryl group.
15. The redox mediator of claim 13 , wherein at least one of R 1 , R 2 , and R′ 1 is coupled to a polymeric backbone.