Amino(oligo)thiophene dyes, preparation thereof, and optical methods of use
Amino(oligo)thiophene dyes useful for studying the electrophysiology of organelles, cells, and tissues are described. Compared to previously known dyes, the amino(oligo)thiophene dyes exhibit improved (faster) response to membrane potential changes, as well as the ability to be excited by 1064 nanometer femtosecond pulses. Methods of preparing the amino( oligo )thiophene dyes are also described.
1. An amino oligo thiophene dye having the structure
wherein m is 1, 2, 3, or 4; n is 2, 3, 4, 5, or 6; R 1 and R 2 are each independently hydrogen or optionally substituted C 1 -C 10 alkyl, C 3 -C 7 cycloalkyl, or phenyl; R 3 is optionally substituted C 1 -C 10 alkyl; R 4 , R 5 , R 6 , and R 7 are each independently hydrogen or fluorine; or R 4 and R 5 collectively form a fused aromatic ring, and/or R 6 and R 7 collectively form a fused aromatic ring; each occurrence of R 8 , R 9 , R 10 , and R 11 is independently hydrogen or halogen, or R 10 and R 11 collectively form ethylenedioxy (—OCH 2 CH 2 O—); provided that at least two adjacent thiophene groups can, optionally, be linked via a fused ring to form a dithiophene unit having the structure
wherein R 12 and R 13 are each independently hydrogen or optionally substituted C 1 -C 6 alkyl; X q− is an anionic counterion wherein q is 1 or 2 or 3; and p is 0, 1, 2, 3, or 4.
2. The amino oligo thiophene dye of claim 1 , wherein m is 1.
3. The amino oligo thiophene dye of claim 1 , wherein n is 2 or 3.
4. The amino oligo thiophene dye of claim 1 , wherein R 1 and R 2 are each independently C 1 -C 4 alkyl or C 1 -C 4 perfluoroalkyl.
5. The amino oligo thiophene dye of claim 1 , wherein R 3 is quaternary ammonium-substituted C 1 -C 10 alkyl or quaternary ammonium-substituted C 1 -C 10 perfluoroalkyl.
6. The amino oligo thiophene dye of claim 1 , wherein R 3 is sulfonate-substituted C 1 -C 10 alkyl or sulfonate-substituted C 1 -C 10 perfluoroalkyl.
7. The amino oligo thiophene dye of claim 1 , wherein at least one of R 8 and R 9 is fluorine.
8. The amino oligo thiophene dye of claim 1 , wherein X q− is selected from the group consisting of hydroxide, fluoride, chloride, bromide, and iodide, sulfite, sulfate, acetate, trifluoroacetate, propionate, succinate, glycolate, stearate, lactate, malate, tartrate, citrate, ascorbate, pamoate, maleate, hydroxymaleate, phenylacetate, glutamate, benzoate, salicylate, sulfanilate, 2-acetoxybenzoate, fumarate, toluenesulfonate, methanesulfonate, ethanesulfonate, ethane disulfonate, benzenesulfonate, toluenesulfonate, oxalate, malonate, succinate, glutarate, adipate, and isethionate.
9. The amino oligo thiophene dye of claim 1 , wherein X q− is bromide.
10. The amino oligo thiophene dye of claim 1 , exhibiting optical properties that are sensitive to its molecular environment.
11. The amino oligo thiophene dye of claim 10 , wherein the optical environmental sensitivity is a second harmonic generation environmental sensitivity of at least 3 percent per 50 millivolts when stimulated with a 1064 nanometer femtosecond fiber laser.
12. The amino oligo thiophene dye of claim 10 , wherein the optical environmental sensitivity is a two photon fluorescence environmental sensitivity of at least 3 percent per 50 millivolts at 615-665 nanometers.
13. An amino oligo thiophene dye having the structure
wherein R 1a and R 2a are each independently C 1 -C 6 alkyl; R 14 is hydrogen or hydroxy; R 15 , R 16 , and R 17 are each independently methyl, ethyl, or 2-hydroxyethyl; and n1 is 2, or 3.
14. An amino oligo thiophene dye having a structure selected from the group consisting of
15. A method of preparing an amino oligo thiophene dye, comprising:
reacting an amine with a bromine-substituted oligo thiophene to form an amino-substituted oligo thiophene; and
reacting the amino-substituted oligo thiophene with a 4-methyl-N-alkyl-pyridinium salt to form the amino oligo thiophene dye;
wherein the amine has the structure HN(R 1 )(R 2 ), wherein R 1 and R 2 are each independently hydrogen or optionally substituted C 1 -C 10 alkyl, C 3 -C 7 cycloalkyl, or phenyl;
wherein the bromine-substituted oligo thiophene has the structure
wherein m is 1, 2, 3, or 4; n is 2, 3, 4, 5, or 6; each occurrence of R 8 , R 9 , R 10 , and R 11 is independently hydrogen or halogen, or R 10 and R 11 collectively form ethylenedioxy (—OCH 2 CH 2 O—), provided that at least two adjacent thiophene groups can, optionally, be linked via a fused ring to form a dithiophene unit having the structure
wherein R 12 and R 13 are each independently hydrogen or optionally substituted C 1 -C 6 alkyl;
wherein the amino-substituted oligo thiophene has the structure
wherein R 1 , R 2 , R 8 , R 9 , R 10 , R 11 , m, and n are as defined above; and
wherein the 4-methyl-N-alkyl-pyridinium salt has the structure
wherein R 3 is optionally substituted C 1 -C 10 alkyl; R 4 , R 5 , R 6 , and R 7 are each independently hydrogen or fluorine; or R 4 and R 5 collectively form a fused aromatic ring, and/or R 6 and R 7 collectively form a fused aromatic ring; X q− is an anionic counterion wherein q is 1 or 2 or 3; and p is 0, 1, 2, 3, or 4; and wherein the amino oligo thiophene dye has the structure
wherein R 1 -R 11 , X, m, n, p, and q are as defined above.
16. A biosensor comprising an amino oligo thiophene dye of claim 1 and, optionally, further comprising a conjugate of a protein and an amino oligo thiophene dye of claim 1 ; wherein the protein of the conjugate is covalently linked to the amino oligo thiophene dye.