Aluminum trihalide-neutral ligand ionic liquids and their use in aluminum deposition
An ionic liquid composition comprising a complex of a trihalo aluminum (III) species with at least one organic uncharged ligand comprising a ring structure having at least three ring carbon atoms and at least one ring heteroatom selected from nitrogen and sulfur, wherein the complex is a liquid at a temperature of 100° C. or less. Methods of electroplating aluminum onto a metallic substrate using the above-described ionic liquid composition are also described.
1. An ionic liquid composition comprising a complex of an aluminum trihalide species with at least one organic uncharged ligand comprising a ring structure having at least three ring carbon atoms and at least one ring heteroatom selected from nitrogen and sulfur, wherein said complex is a liquid at a temperature of 100° C. or less, and wherein said aluminum trihalide and said organic uncharged ligand are present in a molar ratio of 1.1-1.5:1 of said aluminum trihalide to said organic uncharged ligand.
2. The ionic liquid composition of claim 1 , wherein said complex is a liquid at a temperature of 50° C. or less.
3. The ionic liquid composition of claim 1 , wherein said complex is a liquid at a temperature of 30° C. or less.
4. The ionic liquid composition of claim 1 , wherein the ionic liquid composition contains said complex in liquid form in the substantial absence of an organic or inorganic solvent.
5. The ionic liquid composition of claim 1 , wherein said organic uncharged ligand comprises a nitrogen-containing heterocyclic structure having at least three ring carbon atoms and at least one ring nitrogen atom.
6. The ionic liquid composition of claim 5 , wherein said nitrogen-containing heterocyclic structure further comprises at least one alkyl or alkenyl substituent bound to a ring carbon atom.
7. The ionic liquid composition of claim 6 , wherein the alkyl or alkenyl substituent contains at least three carbon atoms.
8. The ionic liquid composition of claim 5 , wherein said nitrogen-containing heterocyclic structure is unsaturated.
9. The ionic liquid composition of claim 8 , wherein said nitrogen-containing heterocyclic structure comprises a pyridine ring.
10. The ionic liquid composition of claim 9 , wherein said pyridine ring is an alkyl- or alkenyl-substituted pyridine ring.
11. The ionic liquid composition of claim 10 , wherein the alkyl or alkenyl substituent contains at least three carbon atoms.
12. A method of electroplating aluminum onto a metallic substrate, the method comprising:
(i) contacting said metallic substrate, in the substantial absence of water, with an ionic liquid composition comprising a complex of an aluminum trihalide species with at least one organic uncharged ligand comprising a ring structure having at least three ring carbon atoms and at least one ring heteroatom selected from nitrogen and sulfur, wherein said complex is a liquid at a temperature of 100° C. or less, and wherein said aluminum trihalide and said organic uncharged ligand are present in a molar ratio of 1.1-1.5:1 of said aluminum trihalide to said organic uncharged ligand, and wherein said ionic liquid composition is in contact with an anode, and
(ii) applying a voltage potential between the anode and said metallic substrate as cathode to produce a coating of aluminum on said metallic substrate while the metallic substrate is in contact with the ionic liquid composition.
13. The method of claim 12 , wherein said metallic substrate is comprised of at least one metal selected from titanium, tantalum, iron, cobalt, nickel, copper, and zinc.
14. The method of claim 12 , wherein said organic uncharged ligand comprises a nitrogen-containing heterocyclic structure having at least three ring carbon atoms and at least one ring nitrogen atom.
15. The method of claim 14 , wherein said nitrogen-containing heterocyclic structure further comprises at least one alkyl or alkenyl substituent bound to a ring carbon atom.
16. The method of claim 15 , wherein the alkyl or alkenyl substituent contains at least three carbon atoms.
17. The method of claim 14 , wherein said nitrogen-containing heterocyclic structure is unsaturated.
18. The method of claim 17 , wherein said nitrogen-containing heterocyclic structure comprises a pyridine ring.
19. The method of claim 18 , wherein said pyridine ring is an alkyl- or alkenyl-substituted pyridine ring.
20. The method of claim 19 , wherein the alkyl or alkenyl substituent contains at least three carbon atoms.
21. The method of claim 12 , wherein the ionic liquid composition contains said complex in liquid form in the substantial absence of an organic or inorganic solvent.
22. The method of claim 21 , wherein step (ii) is conducted at a temperature of up to 100° C., at which temperature said complex is a liquid.
23. The method of claim 21 , wherein step (ii) is conducted at a temperature of up to 50° C., at which temperature said complex is a liquid.
24. The method of claim 21 , wherein step (ii) is conducted at a temperature of up to 30° C., at which temperature said complex is a liquid.
25. The ionic liquid composition of claim 8 , wherein said nitrogen-containing heterocyclic structure comprises a 4-alkyl-pyridine or 4-alkenyl-pyridine ring.
26. The ionic liquid composition of claim 25 , wherein the alkyl or alkenyl substituent contains at least three carbon atoms.
27. The ionic liquid composition of claim 8 , wherein said nitrogen-containing heterocyclic structure comprises an alkyl- or alkenyl-substituted imidazole ring.
28. The ionic liquid composition of claim 27 , wherein the alkyl or alkenyl substituent contains at least three carbon atoms.
29. The ionic liquid composition of claim 1 , wherein said organic uncharged ligand comprises a thiophene ring.
30. The ionic liquid composition of claim 29 , wherein said thiophene ring is an alkyl- or alkenyl-substituted thiophene ring.