New patent application published for: PLANAR CHIRAL METALLOPOLYMER, METHOD OF PREPARING THE SAME, ELECTRODE, AND METHOD FOR ELECTROCHEMICAL ENANTIOSELECTIVE SEPARATION

PLANAR CHIRAL METALLOPOLYMER, METHOD OF PREPARING THE SAME, ELECTRODE, AND METHOD FOR ELECTROCHEMICAL ENANTIOSELECTIVE SEPARATION

Claims

1. A planar chiral metallopolymer, comprising: a polymer backbone; and a plurality of planar chiral metallocene units attached to the polymer backbone, each planar chiral metallocene unit comprising: a metallocene moiety having a first cyclopentadienyl ring, a second cyclopentadienyl ring, and a transition metal; a first functional group attached to the first cyclopentadienyl ring at a first position, the first functional group comprising a chiral moiety providing point chirality; and a second functional group attached to the first cyclopentadienyl ring at a second position adjacent to the first position, the second functional group being different from the first functional group, wherein the first functional group and the second functional group together provide planar chirality to the metallocene moiety.
2. The planar chiral metallopolymer of claim 1, wherein the metallocene moiety is a ferrocene moiety.
3. The planar chiral metallopolymer of claim 1, wherein the planar chiral metallocene units are attached to the polymer backbone through either the first functional group or the second functional group.
4. The planar chiral metallopolymer of claim 1, wherein the first functional group is a 2-oxazolin-2-yl group substituted with a C1-C3 alkyl group, thereby providing a point chirality at the substituted position.
5. The planar chiral metallopolymer of claim 4, wherein the first functional group is a 4-isopropyl-2-oxazolin-2-yl group.
6. The planar chiral metallopolymer of claim 1, wherein the first functional group comprises a moiety represented by Formula I:
—C*(CH.sub.3)H—Z—(CH.sub.2).sub.n—Y—CO—   [Formula I] wherein, in formula I, C* denotes a chiral carbon atom, when Z is a single bond, n is 0, and Y is O or NH, when Z is O or NH, n is 2, and Y is O or NH, the chiral carbon atom denoted as C* is directly bonded to the first cyclopentadienyl ring, and the carbonyl moiety represented by —CO— is directly bonded to the polymer backbone.
7. The planar chiral metallopolymer of claim 1, wherein the second functional group comprises a C1-C3 alkyl group.
8. The planar chiral metallopolymer of claim 1, wherein the second functional group comprises a phenylchalcogen group represented by —SPh, —SePh, or —TePh.
9. The planar chiral metallopolymer of claim 1, wherein the second functional group comprises a group represented by —Si(R.sup.1).sub.3, —P(R.sup.2).sub.2, —X, —CHO, —COOR.sup.3, or N.sub.3, wherein: X is F, Cl, Br, or I, each R.sup.1 is independently hydrogen, a C.sub.1-C.sub.6 alkyl group, or a C.sub.6-C.sub.10 aryl group, each R.sup.2 is independently a C.sub.1-C.sub.6 alkyl group or a C.sub.6-C.sub.10 aryl group, and R.sup.3 is a C.sub.1-C.sub.3 alkyl group.
10. The planar chiral metallopolymer of claim 1, wherein the polymer backbone is a polyethylene backbone, a polystyrene backbone, or a polysiloxane backbone.
11. The planar chiral metallopolymer of claim 1, wherein the combination of the planar chirality and the point chirality in the planar chiral metallocene unit is configured to selectively bind one enantiomer of a chiral target molecule over the enantiomeric counterpart of the chiral target molecule upon electrochemical oxidation.
12. A method of preparing the planar chiral metallopolymer of claim 1, comprising: reacting a 1-substituted metallocene compound with an alkyllithium base to generate a metallocenyllithium intermediate via ortho-lithiation; reacting the metallocenyllithium intermediate with an electrophile comprising a functional group to generate a 1,2-disubstituted metallocene monomer having planar chirality; and polymerizing the 1,2-disubstituted metallocene monomer to form the planar chiral metallopolymer.
13. The method of claim 12, wherein reacting the metallocenyllithium intermediate with the electrophile comprises reacting with DMF to provide a ferrocenyl aldehyde intermediate, followed by a Wittig reaction to introduce a vinyl group, thereby providing the 1,2-disubstituted metallocene monomer; and wherein polymerizing the 1,2-disubstituted metallocene monomer comprises a thiol-ene polymerization with a thiol-functionalized polysiloxane, thereby providing a planar chiral metallopolymer having a polysiloxane backbone.
14. The method of claim 12, wherein reacting the metallocenyllithium intermediate with the electrophile comprises reacting with 1,2-bis(4-vinylphenyl) diselenide or diphenyl diselenide (PhSeSePh) to introduce a (4-vinylphenyl) selenyl group, thereby providing the 1,2-disubstituted metallocene monomer; and wherein polymerizing the 1,2-disubstituted metallocene monomer comprises a free radical polymerization, thereby providing a planar chiral metallopolymer having a polyethylene backbone.
15. The method of claim 12, wherein the 1-substituted metallocene compound comprises Ugi's amine, and the alkyllithium base comprises sec-butyllithium.
16. The method of claim 12, wherein the 1-substituted metallocene compound comprises Ugi's amine, and wherein, before polymerizing the 1,2-disubstituted metallocene monomer, the method further comprises: quaternizing a dimethylamino group of the Ugi's amine to form a quaternary ammonium salt intermediate; and reacting the quaternary ammonium salt intermediate with 2-hydroxyethyl methacrylate.
17. The method of claim 12, wherein the electrophile is selected from the group consisting of PhSeSePh, diphenyl disulfide (PhSSPh), diphenyl ditelluride (PhTeTePh), a halosilane represented by Si(R.sup.1).sub.3X, a halophosphine represented by P(R.sup.2).sub.2X, a haloalkyl represented by R.sup.3X, a molecular halogen represented by X.sub.2, N,N-dimethylformamide (DMF), diethyl carbonate ((R.sup.3O).sub.2CO), and tosyl azide, wherein: X is F, Cl, Br, or I, each R.sup.1 is independently hydrogen, a C.sub.1-C.sub.6 alkyl group, or a C.sub.6-C.sub.10 aryl group, each R.sup.2 is independently a C.sub.1-C.sub.6 alkyl group or a C.sub.6-C.sub.10 aryl group, and R.sup.3 is a C.sub.1-C.sub.3 alkyl group.
18. An electrode for electrochemical enantioselective separation, comprising: an electrically conductive support; and a planar chiral metallopolymer disposed on the electrically conductive support, the planar chiral metallopolymer comprising a plurality of planar chiral metallocene units attached to a polymer backbone, each planar chiral metallocene unit having both planar chirality and point chirality, wherein the combination of the planar chirality and the point chirality is configured to selectively bind one enantiomer of a chiral target molecule over the enantiomeric counterpart of the chiral target molecule upon electrochemical oxidation.
19. The electrode of claim 18, wherein the electrically conductive support comprises a carbon paper, carbon cloth, or carbon felt.
20. A method for electrochemical enantioselective separation of chiral molecules, comprising: contacting the electrode of claim 18 with a solution comprising a mixture of enantiomers of a chiral target molecule, the electrode comprising an electrically conductive support and a planar chiral metallopolymer disposed on the electrically conductive support, the planar chiral metallopolymer having both planar chirality and point chirality; and applying an oxidation potential or an oxidation current to the electrode, whereby the planar chiral metallopolymer selectively binds one enantiomer of the chiral target molecule over the other enantiomer.
21. The method of claim 20, further comprising, after applying the oxidation potential, applying a reduction potential to the electrode to release the bound enantiomer from the planar chiral metallopolymer.
22. The method of claim 20, further comprising, prior to contacting the electrode with the solution, preparing the electrode by forming the planar chiral metallopolymer on the electrically conductive support by a drop-casting method.
23. The method of claim 20, wherein the solution comprises an organic solvent, a protic solvent additive, an electrolyte, or a combination thereof.
24. The method of claim 20, wherein: the organic solvent comprises acetonitrile, the protic solvent additive comprises methanol, or the electrolyte comprises tetrabutylammonium hexafluorophosphate.
25. The method of claim 20, wherein the chiral target molecule is a carboxylate-containing compound or amino acid-containing compound.
26. The method of claim 20, the chiral target molecule is N-Boc-amino acid.
27. The method of claim 20, wherein the oxidation potential is in a range from about 0.25 V to about 0.40 V.
28. The method of claim 20, further comprising repeating the applying of the oxidation potential and the applying of the reduction potential in a cascade electrochemical process comprising a plurality of stages to achieve an enantiomeric excess of greater than 90%.
29. The method of claim 28, wherein the cascade electrochemical process achieves an enantiomeric excess of greater than 99%.