USE OF HALOGEN DERIVATIVES OF HISTIDINE AS ELECTROLYTIC SALT IN A PHOTOVOLTAIC DYE CELL

Abstract

The invention relates to the use of halogenated histidine derivatives as electrolyte salts in the preparation of an electrolyte composition in a photoelectrochemical cell based on the sensitization to light of photoactive molecules, and also to a photoelectrochemical cell based on the sensitization to light of photoactive molecules comprising an electrolyte composition comprising at least one halogenated histidine derivative as electrolyte salt.

Claims

1. An electrolyte salt of following formula (I): ##STR00023## in which: R.sup.1 represents a hydrogen atom or a linear alkyl radical having from 1 to 10 carbon atoms; R.sup.2 and R.sup.4, which are identical or different, each represent a linear or branched alkyl radical having from 1 to 15 carbon atoms, said alkyl radical optionally being substituted by one or more C.sub.6-C.sub.20 aryl groups which can optionally comprise one or more heteroatoms chosen from oxygen, sulfur and nitrogen atoms; R.sup.3 represents a hydrogen atom or a linear or branched alkyl radical having from 1 to 15 carbon atoms, X.sup.− represents an iodide or bromide anion, wherein said electrolyte salt is configured to be included in an electrolyte composition of a photoelectrochemical cell based on the sensitization to light of photoactive molecules.

2. The use as claimed in claim 1, wherein the photoelectrochemical cell based on sensitization to light of photoactive molecules is a dye-sensitized photovoltaic cell.

3. The use as claimed in claim 1, wherein the compounds of formula (I) are chosen from the group consisting of: 4-(3-methoxy-3-oxopropyl)-1,3-dimethyl-1H-imidazol-3-ium iodide, 4-(3-ethoxy-3-oxopropyl)-1,3-dimethyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,3-diethyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,3-dipropyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,3-dibutyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,3-dipentyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,3-dihexyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1-methyl -3-propyl-1H-imidazol-3-ium iodide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1-methyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1-methyl -3-propyl-1H-imidazol-3-ium iodide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1-methyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1-methyl-3-pentyl-1H-imidazol-3-ium iodide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1-methyl-1H-imidazol-3-ium iodide, 1-ethyl-4-(3-methoxy-3-oxopropyl)-3-methyl-1H-imidazol-3-ium iodide, 1,3-diethyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 1-ethyl-4-(3-methoxy-3-oxopropyl)-3-propyl-1H-imidazol-3-ium iodide, 3-butyl-1-ethyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 1-ethyl-4-(3-methoxy-3-oxopropyl)-3-pentyl-1H-imidazol-3-ium iodide, 1-ethyl-3-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-3-methyl -1-propyl-1H-imidazol-3-ium iodide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1-propyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,3-dipropyl-1H-imidazol-3-ium iodide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1-propyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-3-pentyl-1-propyl-1H-imidazol-3-ium iodide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1-propyl-1H-imidazol-3-ium iodide, 1-butyl-4-(3-methoxy-3-oxopropyl)-3-methyl-1H-imidazol-3-ium iodide, 1-butyl-3-ethyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 1-butyl-4-(3-methoxy-3-oxopropyl)-3-propyl -1H-imidazol-3-ium iodide, 1,3-dibutyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 1-butyl-4-(3-methoxy-3-oxopropyl)-3-pentyl-1H-imidazol-3-ium iodide, 1-butyl-3-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-3-methyl-1-pentyl-1H-imidazol-3-ium iodide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1-pentyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1-pentyl-3-propyl -1H-imidazol-3-ium iodide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1-pentyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,3-dipentyl-1H-imidazol-3-ium iodide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1-pentyl-1H-imidazol-3-ium iodide, 1-hexyl-4-(3-methoxy-3-oxopropyl)-3-methyl-1H-imidazol-3-ium iodide, 3-ethyl-1 -hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 1-hexyl-4-(3-methoxy-3-oxopropyl)-3-propyl-1H-imidazol-3-ium iodide, 3-butyl-1-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 1-hexyl-4-(3-methoxy-3-oxopropyl)-3-pentyl-1H-imidazol-3-ium iodide, 1,3-dihexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1-methyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1-methyl-3-propyl-1H-imidazol-3-ium bromide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1-methyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1-methyl -3-pentyl-1H-imidazol-3-ium bromide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1-methyl-1H-imidazol-3-ium bromide, 1-ethyl-4-(3-methoxy-3-oxopropyl)-3-methyl-1H-imidazol-3-ium bromide, 1,3-diethyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 1-ethyl-4-(3-methoxy-3-oxopropyl)-3-propyl-1H-imidazol-3-ium bromide, 3-butyl-1-ethyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 1-ethyl-4-(3-methoxy-3-oxopropyl)-3-pentyl-1H-imidazol-3-ium bromide, 1-ethyl-3-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-3-methyl -1-propyl-1H-imidazol-3-ium bromide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1-propyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1,3-dipropyl-1H-imidazol-3-ium bromide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1-propyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-3-pentyl-1-propyl-1H-imidazol-3-ium bromide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1-propyl-1H-imidazol-3-ium bromide, 1-butyl-4-(3-methoxy-3-oxopropyl)-3-methyl-1H-imidazol-3-ium bromide, 1-butyl-3-ethyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 1-butyl-4-(3-methoxy-3-oxopropyl)-3-propyl-1H-imidazol-3-ium bromide, 1,3-dibutyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 1-butyl-4-(3-methoxy-3-oxopropyl)-3-pentyl-1H-imidazol-3-ium bromide, 1-butyl-3-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-3-methyl-1-pentyl-1H-imidazol-3-ium bromide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1-pentyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1-pentyl-3-propyl -1H-imidazol-3-ium bromide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1-pentyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1,3-dipentyl-1H-imidazol-3-ium bromide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1-pentyl-1H-imidazol-3-ium bromide, 1-hexyl-4-(3-methoxy-3-oxopropyl)-3-methyl-1H-imidazol-3-ium bromide, 3-ethyl-1-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 1-hexyl-4-(3-methoxy-3-oxopropyl)-3-propyl -1H-imidazol-3-ium bromide, 3-butyl-1-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 1-hexyl-4-(3-methoxy-3-oxopropyl)-3-pentyl-1H-imidazol-3-ium bromide, 1,3-dihexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1,2,3-trimethyl-1H-imidazol-3-ium iodide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-3-propyl -1H-imidazol-3-ium iodide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-3-pentyl-1H-imidazol-3-ium iodide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-1H-imidazol-3-ium iodide, 1,3-diethyl-4-(3-methoxy-3-oxopropyl)-2-methyl -1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-2-methyl -1,3-dipropyl-1H-imidazol-3-ium iodide, 1,3-dibutyl-4-(3-methoxy-3-oxopropyl)-2-methyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-2-methyl -1,3-dipentyl-1H-imidazol-3-ium iodide, 1,3-dihexyl-4-(3-methoxy-3-oxopropyl)-2-methyl-1H-imidazol-3-ium iodide, 1-ethyl-3-hexyl-4-(3-methoxy-3-oxopropyl)-2-methyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1-methyl-3-propyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1,2,3-trimethyl-1H-imidazol-3-ium bromide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-3-propyl-1H-imidazol-3-ium bromide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-3-pentyl-1H-imidazol-3-ium bromide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-1H-imidazol-3-ium bromide, 1,3-diethyl-4-(3-methoxy-3-oxopropyl)-2-methyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-2-methyl-1,3-dipropyl-1H-imidazol-3-ium bromide, 1,3-dibutyl-4-(3-methoxy-3-oxopropyl)-2-methyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-2-methyl-1,3-dipentyl-1H-imidazol-3-ium bromide, and 1-ethyl-3-hexyl-4-(3-methoxy-3-oxopropyl)-2-methyl-1H-imidazol-3-ium iodide.

4. A photoelectrochemical cell based on the sensitization to light of photoactive molecules comprising: an assembly forming a photoelectrode comprising: i) a transparent substrate coated with a layer of a transparent and conducting electrode material, ii) a photoactive layer formed on said electrode material, said photoactive layer comprising a transparent carrier material and at least one photoactive molecule; an assembly forming a counterelectrode; and an electrolyte composition interposed between said photoactive layer and said counterelectrode, said cell being said electrolyte composition comprises, in an electrolyte solvent, a reversible redox pair (I.sub.3/I.sup.−) based on molecular iodine and on at least one compound of formula (I) as defined in claim 1.

5. The cell as claimed in claim 4, wherein said cell is a dye-sensitized photovoltaic cell.

6. The cell as claimed in claim 4, wherein the concentration of the compound or compounds of formula (I) within the electrolyte composition varies from 0.1 to 5 mol/l.

7. The cell as claimed in claim 4, wherein the concentration of molecular iodine within the electrolyte composition preferably varies from 0.001 to 0.5 mol/l.

8. The cell as claimed in claim 4, wherein the electrolyte solvent or solvents can be chosen from the group consisting of nitriles; sulfolane; dimethyl sulfoxide; dioxane; tetrahydrofuran; nitromethane; amides; N-methyl-2-pyrrolidinone; carbonates; ethylene glycols; alcohols, ketones; anhydrides; ethers; water; phthalates; adipates; citrates; sebacates; maleates; benzoates and succinates.

9. The cell as claimed in claim 4, wherein the solvent or solvents is an ionic liquid chosen the group consisting of from 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide and their mixtures.

10. The cell as claimed in claim 4, wherein the electrolyte composition additionally includes one or more additives chosen from the group consisting of benzimidazole derivatives; pyridine derivatives; triazole derivatives; pyrazole derivatives; imidazole derivatives; ethylene carbonate; guanidine thiocyanate and chenodeoxycholic acid; magnesium iodide; and alkali metal salts of formula LiY or NaY in which Y is an I.sup.−, Br.sup.−, trifluorosulfonate, ClO.sub.4.sup.−, NO.sub.3.sup.− or TFSI.sup.− anion.

11. The cell as claimed in claim 4, wherein the transparent substrate of the photoelectrode is made of a flexible or rigid material chosen from glass or a sheet made of a plastic material.

12. The cell as claimed in claim 4, wherein the electrode material of the photoelectrode is applied to the transparent substrate and is provided in the form of a layer of a transparent conducting oxide chosen from the group consisting of tin oxide doped with fluorine, indium tin oxide, indium oxide doped with antimony and zinc oxide doped with aluminum, with gallium or with indium.

13. The cell as claimed in claim 4, wherein the photoactive molecule of the photoactive layer is a ruthenium or osmium complex.

14. The cell as claimed in claim 4, wherein the counterelectrode is made of a transparent countersubstrate coated with a layer of SnO.sub.2:F or of doped ZnO or with a stack of transparent conducting layers and in that a layer of catalyst is formed on the material forming counterelectrode.

15. The cell as claimed in claim 14, wherein the layer of catalyst is a layer of platinum or of carbon or of inorganic chalcogenide.

16. The compounds of following formula (I′): ##STR00024## in which: R.sup.1 resents a hydrogen atom or a linear alkyl radical having from 1 to 10 carbon atoms, R.sup.2 and R.sup.4, which are identical or different, each represent a linear or branched alkyl radical having from 1 to 15 carbon atoms, said alkyl radical optionally being substituted by one or more C.sub.6-C.sub.20 aryl groups which can optionally comprise one or more heteroatoms chosen from oxygen, sulfur and nitrogen atoms, R.sup.3 represents a hydrogen atom or a linear or branched alkyl radical having from 1 to 15 carbon atoms, X.sup.− represents an iodide or bromide anion, wherein: when X.sup.− represents an iodide anion, when le represents a methyl radical and when R.sup.3 is a hydrogen atom, then the R.sup.2 and R.sup.4 radicals cannot simultaneously represent a methyl radical or an ethyl radical, when X.sup.− represents a bromide anion, when le represents a methyl radical and when R.sup.3 is a hydrogen atom, then the R.sup.2 and R.sup.4 radicals cannot simultaneously represent a benzyl radical, when X.sup.− represents a bromide anion, when le represents a methyl radical, when R.sup.2 is a butyl radical and when R.sup.3 is a hydrogen atom, then the R.sup.4 radical is other than a methyl, ethyl or benzyl radical, when X.sup.− represents an iodide anion, when R.sup.1 and R.sup.2 represent a methyl radical and when R.sup.3 is a hydrogen atom, then the R.sup.4 radical is other than a trityl radical, and when X.sup.− represents a bromide anion, when le represents a methyl radical, when R.sup.2 is a butyl radical and when R.sup.3 is an isopropyl radical, then the R.sup.4 radical is other than a methyl radical.

17. The compound of formula (I′) as claimed in claim 16, wherein said compound of formula (I′) is chosen from: 4-(3-ethoxy-3-oxopropyl)-1,3-dimethyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,3-dipropyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,3-dibutyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,3-dipentyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,3-dihexyl-1H-imidazol-3-ium iodide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1-methyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1-methyl-3-propyl-1H-imidazol-3-ium iodide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1-methyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1-methyl-3-pentyl-1H-imidazol-3-ium iodide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1-methyl-1H-imidazol-3-ium iodide, 1-ethyl-4-(3-methoxy-3-oxopropyl)-3-methyl-1H-imidazol-3-ium iodide, 1-ethyl-4-(3-methoxy-3-oxopropyl)-3-propyl-1H-imidazol-3-ium iodide, 3-butyl-1-ethyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 1-ethyl-4-(3-methoxy-3-oxopropyl)-3-pentyl-1H-imidazol-3-ium iodide, 1-ethyl-3-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-3-methyl-1-propyl-1H-imidazol-3-ium iodide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1-propyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,3-dipropyl-1H-imidazol-3-ium iodide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1-propyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-3-pentyl-1-propyl-1H-imidazol-3-ium iodide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1-propyl-1H-imidazol-3-ium iodide, 1-butyl-4-(3-methoxy-3-oxopropyl)-3-methyl-1H-imidazol-3-ium iodide, 1-butyl-3-ethyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 1-butyl-4-(3-methoxy-3-oxopropyl)-3-propyl-1H-imidazol-3-ium iodide, 1,3-dibutyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 1-butyl-4-(3-methoxy-3-oxopropyl)-3-pentyl-1H-imidazol-3-ium iodide, 1-butyl-3-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-3-methyl-1-pentyl-1H-imidazol-3-ium iodide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1-pentyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1-pentyl-3-propyl-1H-imidazol-3-ium iodide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1-pentyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,3-dipentyl-1H-imidazol-3-ium iodide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1-pentyl-1H-imidazol-3-ium iodide, 1-hexyl-4-(3-methoxy-3-oxopropyl)-3-methyl-1H-imidazol-3-ium iodide, 3-ethyl-l-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 1-hexyl-4-(3-methoxy-3-oxopropyl)-3-propyl-1H-imidazol-3-ium iodide, 3-butyl-1-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 1-hexyl-4-(3-methoxy-3-oxopropyl)-3-pentyl-1H-imidazol-3-ium iodide, 1,3-dihexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium iodide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1-methyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1-methyl-3-propyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1-methyl-3-pentyl-1H-imidazol-3-ium bromide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1-methyl-1H-imidazol-3-ium bromide, 1-ethyl-4-(3-methoxy-3-oxopropyl)-3-methyl-1H-imidazol-3-ium bromide, 1,3-diethyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 1-ethyl-4-(3-methoxy-3-oxopropyl)-3-propyl-1H-imidazol-3-ium bromide, 1-ethyl-4-(3-methoxy-3-oxopropyl)-3-pentyl-1H-imidazol-3-ium bromide, 1-ethyl-3-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-3-methyl-1-propyl-1H-imidazol-3-ium bromide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1-propyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1,3-dipropyl-1H-imidazol-3-ium bromide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1-propyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-3-pentyl-1-propyl-1H-imidazol-3-ium bromide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1-propyl-1H-imidazol-3-ium bromide, 1-butyl-4-(3-methoxy-3-oxopropyl)-3-propyl-1H-imidazol-3-ium bromide, 1,3-dibutyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 1-butyl-4-(3-methoxy-3-oxopropyl)-3-pentyl-1H-imidazol-3-ium bromide, 1-butyl-3-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-3-methyl-1-pentyl-1H-imidazol-3-ium bromide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1-pentyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1-pentyl-3-propyl-1H-imidazol-3-ium bromide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1-pentyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1,3-dipentyl-1H-imidazol-3-ium bromide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1-pentyl-1H-imidazol-3-ium bromide, 1-hexyl-4-(3-methoxy-3-oxopropyl)-3-methyl-1H-imidazol-3-ium bromide, 3-ethyl-l-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 1-hexyl-4-(3-methoxy-3-oxopropyl)-3-propyl-1H-imidazol-3-ium bromide, 3-butyl-1-hexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 1-hexyl-4-(3-methoxy-3-oxopropyl)-3-pentyl-1H-imidazol-3-ium bromide, 1,3-dihexyl-4-(3-methoxy-3-oxopropyl)-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1,2,3-trimethyl-1H-imidazol-3-ium iodide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-3-propyl-1H-imidazol-3-ium iodide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-3-pentyl-1H-imidazol-3-ium iodide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-1H-imidazol-3-ium iodide, 1,3-diethyl-4-(3-methoxy-3-oxopropyl)-2-methyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-2-methyl-1,3-dipropyl-1H-imidazol-3-ium iodide, 1,3-dibutyl-4-(3-methoxy-3-oxopropyl)-2-methyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-2-methyl-1,3-dipentyl-1H-imidazol-3-ium iodide, 1,3-dihexyl-4-(3-methoxy-3-oxopropyl)-2-methyl-1H-imidazol-3-ium iodide, 1-ethyl-3-hexyl-4-(3-methoxy-3-oxopropyl)-2-methyl-1H-imidazol-3-ium iodide, 4-(3-methoxy-3-oxopropyl)-1-methyl -3-propyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1,2,3-trimethyl-1H-imidazol-3-ium bromide, 3-ethyl-4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-3-propyl -1H-imidazol-3-ium bromide, 3-butyl-4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-3-pentyl-1H-imidazol-3-ium bromide, 3-hexyl-4-(3-methoxy-3-oxopropyl)-1,2-dimethyl-1H-imidazol-3-ium bromide, 1,3-diethyl-4-(3-methoxy-3-oxopropyl)-2-methyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-2-methyl-1,3-dipropyl-1H-imidazol-3-ium bromide, 1,3-dibutyl-4-(3-methoxy-3-oxopropyl)-2-methyl-1H-imidazol-3-ium bromide, 4-(3-methoxy-3-oxopropyl)-2-methyl -1,3-dipentyl-1H-imidazol-3-ium bromide, and 1-ethyl-3-hexyl-4-(3-methoxy-3-oxopropyl)-2-methyl-1H-imidazol-3-ium iodide.

Description

EXAMPLES

[0280] The following starting materials were used in the examples: [0281] N-butylbenzimidazole (Merck); [0282] Urocanic acid; anhydrous methanol; sodium sulfuret; concentrated sulfuric acid; sodium carbonate; cyclohexane; 10% palladium-on-charcoal (10% Pd/C); potassium carbonate; methyl iodide; ethyl iodide; potassium iodide; 1-bromopropane; 1-iodopropane; 1-iodobutane; 1-iodopentane; 1-iodohexane; molecular iodine; guanidinium thiocyanate (Sigma-Aldrich); [0283] Ethyl acetate; acetone, dichloromethane (VWR); [0284] 3-Methoxypropionitrile (Alfa Aesar); [0285] 1,3-Dimethylimidazolium iodide (DMII) (Solvionic).

Example 1

Synthesis of 4-(3-methoxy-3-oxopropyl)-1,3-dimethyl-1H-imidazol-3-ium iodide (compound 3a)

[0286] In this example, the synthesis has been carried out of a compound of formula (I) in which the R.sup.1, R.sup.2 and R.sup.4 radicals are identical and represent a methyl radical, R.sup.3 representing a hydrogen atom:

##STR00010##

[0287] 1) First Stage: Synthesis of the Methyl Ester of Urocanic Acid (Compound 1)

##STR00011##

[0288] 11.5 ml of concentrated sulfuric acid were added to a solution of urocanic acid (20 g, 145 mmol) and sodium sulfurte (2.8 g) in anhydrous methanol (215 ml). After stirring at 70° C. overnight, the reaction mixture was cooled to ambient temperature and filtered. The solvent was subsequently removed under reduced pressure and water was added (1 ml). The solution thus obtained was neutralized to neutral pH by addition of a saturated sodium carbonate solution. The solution was subsequently extracted 4 times with ethyl acetate and then the organic phases were combined and dried over sodium sulfurte. The solvent was subsequently removed under reduced pressure. After dissolution of the precipitate with a minimum amount of ethyl acetate, 300 ml of cyclohexane were added. After filtration, the expected compound 1 was obtained in the form of a white solid (20 g, yield 92%).

[0289] Melting point: 74-76° C.

[0290] .sup.1H NMR (d.sub.6-DMSO 300 MHz): δ (ppm) 7.80 (s, 1 H, NCHN); 7.55 (d, 1 H, J=15.6 Hz, CH═CH); 7.51 (s, 1 H, NCH); 6.40 (d, 1 H, J=15.6 Hz, CH═CH); 3.65 (s, 3 H, OCH.sub.3)

[0291] .sup.13C NMR (d.sub.6-DMSO 75 MHz): δ (ppm) 167.7 (CO); 138.2 (NCHN); 136.3 (CH═); 134.7 (Cq); 123.9 (CH═); 111.1 (NCH); 51.5 (OCH.sub.3).

[0292] Molar mass calculated for C.sub.7H.sub.8N.sub.2O.sub.2Na.sup.+: 175 g•mol.sup.−1; found 175 g•mol.sup.−1.

[0293] 2) Second Stage: Synthesis of Methyl 3-(1H-Imidazol-4-Yl)Propanoate Compound 2)

##STR00012##

[0294] 1.5 g of 10% Pd/C were added to a solution of 20 g (133 mmol) of the methyl ester of urocanic acid (compound la obtained in the preceding stage 1)) in 150 ml of methanol under molecular hydrogen pressure. After hydrogenating at ambient temperature for 14 hours, the reaction medium was filtered through celite. The filtrate was subsequently evaporated under reduced pressure to result in 19.6 g of the expected compound 2 (yield 95%) in the form of a slightly orange syrup.

[0295] .sup.1H NMR (CDCl.sub.3, 300 MHz): δ (ppm) 9.65 (s, 1 H, NCHN); 7.55 (s, 1 H, NCH); 6.77 (s, 1 H, NH); 3.61 (s, 3 H, OCH.sub.3); 2.90 (t, 2 H, J=7.5 Hz, CH.sub.2); 2.63 (t, 2 H, J=7.5 Hz, CH.sub.2)

[0296] .sup.13C NMR (CDCl.sub.3, 75 MHz): δ (ppm) 173.6 (CO); 135.6 (Cq); 134.7 (NCHN); 116.7 (NCH); 51.6 (OCH.sub.3); 33.8 (CH.sub.2); 22.1 (CH.sub.2).

[0297] Molar mass calculated for C.sub.7H.sub.10N.sub.2O.sub.2Na.sup.+: 177 g/mol; found 177 g/mol.

[0298] 3) Third Stage: Synthesis of 4-(3-Methoxy-3-Oxopropyl)-1,3-Diimethyl-1H-Imidazol-3-Ium Iodide (Compound 3a)

[0299] 5 g of the compound 2 obtained above in the preceding stage (32.4 mmol), 9 g of potassium carbonate (65 mmol) and 8.1 ml of methyl iodide were added to 100 ml of acetone. The reaction mixture was maintained at 70° C. with stirring for 1 hour. After cooling to ambient temperature, the reaction mixture was filtered and the solvent was removed under reduced pressure. The precipitate formed was dissolved in dichloromethane, the mixture was then filtered and the solvent was removed under reduced pressure. The reaction mixture was subsequently triturated in cyclohexane and the solid was filtered to result in 8.6 g of expected compound 3a in the form of a white solid (yield 86%).

[0300] Melting point: 134.7° C.

[0301] .sup.1H NMR (CDCl.sub.3, 300 MHz): δ (ppm) 9.76 (s, 1 H, NCHN); 7.35 (s, 1 H, NCH); 3.99; 3.94 (s, 6 H, 2×NCH.sub.3); 3.64 (s, 3 H, OCH.sub.3); 2.95 (dd, 2 H, J=6.5 Hz, J=7.5 Hz, CH.sub.2); 2.73 (t, 2 H, J=7.0 Hz, CH.sub.2)

[0302] .sup.13C NMR (CDCl.sub.3, 75 MHz): δ (ppm) 171.7 (CO); 136.7 (NCHN); 134.5 (Cq); 120.7 (NCH); 52.2 (OCH.sub.3); 36.9; 34.4 (2×NCH.sub.3); 31.8 (CH.sub.2); 18.9 (CH.sub.2).

[0303] Molar mass calculated for C.sub.9H.sub.15N.sub.2O.sub.2.sup.+: 183 g/mol; found 183 g/mol.

[0304] A calorimetric analysis under air of the compound 3a was carried out using a calorimeter sold under the trade name DSC204 F1 by Netzsch.

[0305] A thermogravimetric analysis under air of the compound 3a was also carried out after storage exposed to the air for 3 weeks.

[0306] By way of comparison, a thermogravimetric analysis of an imidazolium iodide not coming within the invention, namely 1,3-dimethylimidazolium iodide (DMII), was also carried out.

[0307] The results obtained are given in the appended FIGS. 1 and 2. FIG. 1 gives the results of the calorimetric analysis of the compound 3a. In this figure, the heat flux (in W/g) is a function of the temperature (in ° C.). FIG. 2 gives the results of the thermogravimetric analysis for the compound 3a (continuous line) in comparison with the DMII (noncontinuous line).

[0308] The results of the thermogravimetric analysis under air show that the compound 3a is particularly stable up to a temperature of 300° C., thus well beyond the conditions of accelerated aging of thin film photovoltaic cells laid down by the standard IEC 61646, which is 1000 hours at 60° C./100 mW.cm.sup.−2 under illumination and 1000 hours at 85° C. in the dark. In comparison, DMII allows a loss in weight of the order of 30% originating from the water captured as a result of its hygroscopicity. In contrast, even after storage of the compound 3a exposed to the air for 3 weeks, this compound does not exhibit any hygroscopicity nature, which opens it to use and to storage outside glove boxes or dry rooms.

Example 2

Synthesis of 4-(3-methoxy-3-oxopropyl)-1,3-diethyl-1H-imidazol-3-ium iodide (compound 3b)

[0309] In this example, the synthesis was carried out of a compound of formula (I) in which R.sup.1 is a methyl radical and the R.sup.2 and R.sup.4 radicals are identical and represent an ethyl radical, R.sup.3 representing a hydrogen atom:

##STR00013##

[0310] 5 g of the compound 2 obtained above in stage 2) of example 1 (32 4 mmol), 9 g of potassium carbonate (65 mmol) and 7.8 ml of ethyl iodide were added to 100 ml of acetone. The reaction mixture was maintained at 70° C. with stirring overnight. After cooling to ambient temperature, the reaction mixture was filtered and the solvent was removed under reduced pressure. The precipitate formed was dissolved in dichloromethane, the mixture was then filtered and the solvent was removed under reduced pressure. The reaction mixture was subsequently triturated in cyclohexane and the solid was filtered off to result in 9.5 g of the expected compound 3b in the form of a light yellow solid (yield 86%).

[0311] Melting point: 111° C.

[0312] .sup.1H NMR (CDCl.sub.3, 300 MHz): δ (ppm) 9.86 (s, 1 H, NCHN); 7.41 (s, 1 H, NCH); 4.30 (dd, 2 H, J=7.3 Hz, J=14.7 Hz, NCH.sub.2); 4.24 (dd, 2 H, J=7.3 Hz, J=14.7 Hz, NCH.sub.2); 3.61 (s, 3 H, OCH.sub.3); 2.92 (m, 2 H, CH.sub.2); 2.72 (t, 2 H, J=6.7 Hz, CH.sub.2); 1.52 (m, 6 H, 2×CH.sub.3)

[0313] .sup.13C NMR (CDCl.sub.3, 75 MHz): δ (ppm) 171.8 (CO); 135.2 (NCHN); 133.8 (Cq); 119.2 (NCH); 52.1 (OCH.sub.3); 45.2; 42.6 (2×NCH.sub.2); 31.8 (CH.sub.2); 18.9 (CH.sub.2); 15.6; 15.5 (2×CH.sub.3)

[0314] Molar mass calculated for C.sub.11H.sub.19N.sub.2O.sub.2.sup.+: 211.1447 g/mol; found 211.1446 g/mol.

Example 3

Synthesis of 4-(3-methoxy-3-oxopropyl)-1,3-dipropyl-1H-imidazol-3-ium iodide (compound 3c)

[0315] In this example, the synthesis was carried out of a compound of formula (I) in which R.sup.1 is a methyl radical and the R.sup.2 and R.sup.4 radicals are identical and represent a propyl radical, R.sup.3 representing a hydrogen atom:

##STR00014##

[0316] 4.6 g of a compound 2 obtained above in stage 2) of example 1 (29 7 mmol), 8.2 g of potassium carbonate (59.4 mmol) and 8.7 ml of 1-iodopropane were added to 100 ml of acetone. The reaction mixture was maintained at 70° C. under stirring for 3 days. After cooling to ambient temperature, the reaction mixture was filtered and the solvent was removed under reduced pressure. After purifying through silica gel (methanol/ethyl acetate 10/90), 3.8 g of the compound 3c are obtained in the form of a viscous orange liquid (yield 25%).

[0317] .sup.1H NMR (d6-DMSO, 300 MHz): δ (ppm) 9.25 (s, 1 H, NCHN); 7.66 (s, 1 H, NCH); 4.13 (m, 4 H, 2×NCH.sub.2); 3.63 (s, 3 H, OCH.sub.3); 2.93 (m, 2 H, CH.sub.2); 2.75 (m, 2 H, CH.sub.2); 1.81 (m, 4 H, 2×CH.sub.2); 0.88 (m, 6 H, 2×CH.sub.3)

[0318] .sup.13C NMR (d6-DMSO, 75 MHz): δ (ppm) 172.3 (CO); 136.0 (NCHN); 134.2 (Cq); 119.6 (NCH); 52.1 (OCH.sub.3); 50.8; 48.2 (2×NCH.sub.2); 31.5; 23.1; 22.8; 18.8 (4×CH.sub.2); 10.9; 10.8 (2×CH.sub.3)

[0319] Molar mass calculated for C.sub.13H.sub.23N.sub.2O.sub.2.sup.+: 239.1760 g/mol; found 239.1760 g/mol.

Example 4

Synthesis of 4-(3-methoxy-3-oxopropyl)-1,3-dibutyl-1H-imidazol-3-ium iodide (compound 3d)

[0320] In this example, the synthesis was carried out of a compound of formula (I) in which R.sup.1 is a methyl radical and the R.sup.2 and R.sup.4 radicals are identical and represent a butyl radical, R.sup.3 representing a hydrogen atom:

##STR00015##

[0321] 5 g of the compound 2 obtained above in stage 2) of example 1 (32 4 mmol), 8.9 g of potassium carbonate (65 mmol) and 11.1 ml of 1-iodobutane were added to 100 ml of acetone. The reaction mixture was maintained at 70° C. with stirring for 3 days. After cooling to ambient temperature, the reaction mixture was filtered and the solvent was removed under reduced pressure. After purification through silica gel (methanol/ethyl acetate 10/90), 5.8 g of the compound 3d are obtained in the form of a viscous orange liquid (yield 45%).

[0322] .sup.1H NMR (d.sub.6-DMSO, 300 MHz): δ (ppm) 9.35 (s, 1 H, NCHN); 7.71 (s, 1 H, NCH); 4.17 (m, 4 H, 2×NCH.sub.2); 3.61 (s, 3 H, OCH.sub.3); 2.93 (t, 2 H, J=7.2 Hz, CH.sub.2); 2.74 (t, 2 H, J=7.2 Hz, CH.sub.2); 1.76 (m, 4 H, 2×CH.sub.2); 1.26 (m, 4 H, 2×CH.sub.2); 0.88 (m, 6 H, 2×CH.sub.3)

[0323] .sup.13C NMR (d6-DMSO, 75 MHz): δ (ppm) 172.3 (CO); 135.9 (NCHN); 134.0 (Cq); 119.7 (NCH); 52.2 (OCH.sub.3); 49.0; 46.6 (2×NCH.sub.2); 31.7; 31.6; 31.3; 19.4; 19.2; 18.9 (6×CH.sub.2); 13.8, 13.7 (2×CH.sub.3)

[0324] Molar mass calculated for C.sub.15H.sub.27N.sub.2O.sub.2.sup.+: 267.2073; found 267.2081.

Example 5

Synthesis of 4-(3-methoxy-3-oxopropyl)-1,3-dipentyl-1H-imidazol-3-ium iodide (compound 3e)

[0325] In this example, the synthesis was carried out of a compound of formula (I) in which R.sup.1 is a methyl radical and the R.sup.2 and R.sup.4 radicals are identical and represent a pentyl radical, R.sup.3 representing a hydrogen atom:

##STR00016##

[0326] 5 g of the compound 2 obtained above in stage 2) of example 1 (32 4 mmol), 8.9 g of potassium carbonate (65 mmol) and 11.1 ml of 1-iodopentane were added to 100 ml of acetone. The reaction mixture was maintained at 70° C. with stirring for 3 days. After cooling to ambient temperature, the reaction mixture was filtered and the solvent was removed under reduced pressure. After purification through silica gel (methanol/ethyl acetate 10/90), 10.6 g of the compound 3e are obtained in the form of a viscous orange liquid (yield 79%).

[0327] .sup.1H NMR (d.sub.6-DMSO, 300 MHz): δ (ppm) 9.25 (s, 1 H, NCHN); 7.66 (s, 1 H, NCH); 4.15 (t, 4 H, J=7.4 Hz, 2×NCH.sub.2); 3.63 (s, 3 H, OCH.sub.3); 2.93 (t, 2 H, J=7.2 Hz, CH.sub.2); 2.76 (t, 2 H, J=7.2 Hz, CH.sub.2); 1.79 (m, 4 H, 2×CH.sub.2); 1.29 (m, 8 H, 4 x CH.sub.2); 0.88 (m, 6 H, 2×CH.sub.3) .sup.13C NMR (d6-DMSO, 75 MHz): δ (ppm) 172.3 (CO); 136.0 (NCHN); 134.1 (Cq); 119.6 (NCH); 52.1 (OCH.sub.3); 49.3; 46.7 (2×NCH.sub.2); 31.5; 29.3; 29.0; 28.2;

[0328] 28.0; 22.0; 21.9, 18.8 (8×CH.sub.2); 14. (2×CH.sub.3)

[0329] Molar mass calculated for C.sub.17H.sub.31N.sub.2O.sub.2.sup.+: 295.2386 g/mol; found 295.2382 g/mol.

Example 6

Synthesis of 4-(3-methoxy-3-oxopropyl)-1,3-dihexyl-1H-imidazol-3-ium iodide (compound 3f)

[0330] In this example, the synthesis was carried out of a compound of formula (I) in which R.sup.1 is a methyl radical and R.sup.2 and R.sup.4 radicals are identical and represent a hexyl radical, R.sup.3 representing a hydrogen atom:

##STR00017##

[0331] 5 g of the compound 2 obtained above in stage 2) of example 1 (32 4 mmol), 8.9 g of potassium carbonate (65 mmol) and 14.3 ml of 1-iodohexane were added to 100 ml of acetone. The reaction mixture was maintained at 70° C. with stirring for 3 days. After cooling to ambient temperature, the reaction mixture was filtered and the solvent was removed under reduced pressure. After purification through silica gel (methanol/ethyl acetate 10/90), 11.6 g of the compound 3f are obtained in the form of a viscous orange liquid (yield 79%).

[0332] .sup.1H NMR (d.sub.6-DMSO, 300 MHz): δ (ppm) 9.31 (s, 1 H, NCHN); 7.69 (s, 1 H, NCH); 4.16 (t, 4 H, J=7.2 Hz, 2×NCH.sub.2); 3.62 (s, 3 H, OCH.sub.3); 2.93 (t, 2 H, J=7.2 Hz, CH.sub.2); 2.76 (t, 2 H, J=7.2 Hz, CH.sub.2); 1.78 (m, 4 H, 2×CH.sub.2); 1.29 (m, 12 H, 6×CH.sub.2); 0.85 (m, 6 H, 2×CH.sub.3)

[0333] .sup.13C NMR (d6-DMSO, 75 MHz): δ (ppm) 172.3 (CO); 136.0 (NCHN); 134.1 (Cq); 119.6 (NCH); 52.1 (OCH.sub.3); 49.3; 46.8 (2×NCH.sub.2); 31.5; 31.0; 30.9; 29.6; 29.3; 25.7; 25.5; 22.3; 18.9 (10 x CH.sub.2); 14.2 (2×CH.sub.3)

[0334] Molar mass calculated for C.sub.19H.sub.35N.sub.2O.sub.2.sup.+: 323.2699 g/mol; found 323.2691 g/mol.

Example 7

Synthesis of 4-(3-ethoxy-3-oxopropyl)-1,3-dimethyl-1H-imidazol-3-ium iodide (compound 6)

[0335] In this example, the synthesis was carried out of a compound of formula (I) in which the R.sup.2 and R.sup.4 radicals are identical and represent a methyl radical and R.sup.1 represents an ethyl radical, R.sup.3 representing a hydrogen atom:

##STR00018##

[0336] 1) First Stage: Synthesis of the Ethyl Ester of Urocanic Acid (Compound 4)

##STR00019##

[0337] 14.3 ml of concentrated sulfuric acid were added to a solution of urocanic acid (25 g, 181 mmol) and sodium sulfurte (3.5 g) in anhydrous ethanol (165 ml). After stirring at 70° C. overnight, the reaction mixture was cooled to ambient temperature and filtered. The solvent was subsequently removed under reduced pressure and water was added (1 ml). The solution thus obtained was neutralized to neutral pH by addition of a saturated sodium carbonate solution. The solution was subsequently extracted 4 times with ethyl acetate and then the organic phases were combined and dried over sodium sulfurte. The solvent was subsequently removed under reduced pressure. After dissolution of the precipitate with a minimum amount of ethyl acetate, 300 ml of cyclohexane were added. After filtration, the expected compound 4 was obtained in the form of a white solid (29 g, yield 96%).

[0338] Melting point: 81-82° C.

[0339] .sup.1H NMR (d.sub.6-DMSO, 400 MHz): δ (ppm) 7.78 (s, 1 H, NCHN); 7.54 (s, 1 H, N═CH); 7.53 (d, 1 H, J.sub.a,b=15.6 Hz, H.sub.a CH═); 6.33 (d, 1 H, J.sub.a,b=15.6 Hz, H.sub.b CH═); 4.15 (q, 2 H, J.sub.CH2,CH3=7.1 Hz, CH.sub.2); 1.23 (t, 3 H, J.sub.CH2,CH3=7.1 Hz, CH.sub.3)

[0340] .sup.13C NMR (d6-DMSO, 100 MHz): δ (ppm) 167.0 (CO); 138.2 (NCH═, CH═), 114.0 (CH═, NCH═); 60.0 (CH.sub.2); 14.7 (CH.sub.3)

[0341] Molar mass calculated for C.sub.8H.sub.12N.sub.2O.sub.2Na: 191.0796 g/mol; found 191.0800 g/mol.

[0342] 2) Second Stage: Synthesis of Ethyl 3-(1H-Imidazol-4-Yl)Propanoate Compound 5)

##STR00020##

[0343] 1.8 g of 10% Pd/C were added to a solution of 25 g (150 mmol) of ethyl ester of urocanic acid (compound 4 obtained in the preceding stage 1)) in 150 ml of methanol under molecular hydrogen pressure. After hydrogenating at ambient temperature for 14 hours, the reaction medium was filtered through celite. The filtrate was subsequently evaporated under reduced pressure to result in 23 g of the expected compound 5 (yield 91%) in the form of a slightly orange syrup.

[0344] .sup.1H NMR (d.sub.6-DMSO, 400 MHz): δ (ppm) 7.55 (s, 1 H, NCHN); 6.78 (s, 1 H, N═CH); 4.04 (q, 2 H, J.sub.CH2,CH3=7.2 Hz, CH.sub.2CH.sub.3); 2.78 (t, 2 H, J.sub.CH2,CH2=7.8 Hz, CH.sub.2CH.sub.2); 2.59 (t, 2 H, J.sub.CH2,CH2=7.8 Hz, CH.sub.2); 1.15 (t, 3 H, J.sub.CH2,CH3=7.2 Hz, CH.sub.2CH.sub.3)

[0345] .sup.13C NMR (d.sub.6-DMSO, 100 MHz): δ (ppm) 172.7 (CO); 136.1 (Cq); 135.0 (CH═); 116.5 (CH═); 60.2 (CH.sub.2CH.sub.3); 33.9 (CH.sub.2); 22.6 (CH.sub.2); 14.7 (CH.sub.2CH.sub.3)

[0346] Molar mass calculated for C.sub.8H.sub.10N.sub.2O.sub.2Na: 189.0640 g/mol; found 189.0638 g/mol.

[0347] 3) Third stage: Synthesis of 4-(3-Ethoxy-3-Oxopropyl)-1,3-Dimethyl-1H-Imidazol-3-Ium Iodide (Compound 6)

[0348] 5 g of the compound 5 obtained above in the preceding stage (29 7 mmol), 8.3 g of potassium carbonate (149 mmol) and 9.2 ml of methyl iodide were added to 100 ml of acetone. The reaction mixture was maintained at 70° C. under stirring overnight. After cooling to ambient temperature, the reaction mixture was filtered and the solvent was removed under reduced pressure. The precipitate formed was dissolved in dichloromethane, the mixture was then filtered and the solvent was removed under reduced pressure. The reaction mixture was subsequently triturated in cyclohexane and the solid was filtered off to result in 6.9 g of the expected compound 6 in the form of a white solid (yield 57%).

[0349] .sup.1H NMR (d.sub.6-DMSO, 400 MHz): δ (ppm) 7.55 (s, 1 H, NCHN); 6.78 (s, 1 H, N═CH); 4.04 (q, 2 H, J.sub.CH2,CH3=7.2 Hz, CH.sub.2CH.sub.3); 2.78 (t, 2 H, J.sub.CH2,CH2=7.8 Hz, CH.sub.2CH.sub.2); 2.59 (t, 2 H, J.sub.CH2,CH2=7.8 Hz, CH.sub.2); 1.15 (t, 3 H, J.sub.CH2,CH3=7.2 Hz, CH.sub.2CH.sub.3)

[0350] .sup.13C NMR (d.sub.6-DMSO, 100 MHz): δ (ppm) 171.9 (CO); 136.9 (CH═); 134.4 (Cq); 120.6 (CH═); 60.7 (CH.sub.2CH.sub.3); 36.2 (NCH.sub.3); 33.7 (NCH.sub.3); 31.6 (CH.sub.2); 18.6 (CH.sub.2); 14.5 (CH.sub.2CH.sub.3)

[0351] Molar mass calculated for C.sub.10H.sub.17N.sub.2O.sub.2Na: 197.1290 g/mol; found 197.1289 g/mol.

Example 8

Synthesis of 4-(3-methoxy-3-oxopropyl)-1-methyl-3-propyl-1H-imidazol-3-ium iodide (compound 8)

[0352] In this example, the synthesis was carried out of a compound of formula (I) in which the R.sup.1 and R.sup.2 radicals are identical and represent a methyl radical, R.sup.3 represents a hydrogen atom and R.sup.4 represents a propyl radical:

##STR00021##

[0353] 1) First Stage: Synthesis of Methyl 3-(1-Propyl-1H-Imidazol-4-Yl)Propanoate Compound 7)

##STR00022##

[0354] 3.9 g (31.9 mmol) of 1-bromopropane were added to a solution of 4.9 g (31.9 mmol) of the compound 2 obtained above in stage 2) of example 1, of 5.3 g (31.9 mmol) of potassium iodide and of 8.8 g (63.9 mmol) of potassium carbonate in 100 ml of acetone. The reaction mixture was maintained at 70° C. under stirring overnight and then filtered. The solvent was removed under reduced pressure. After flash chromatography through silica gel (eluent 100% ethyl acetate and then a methanol/ethyl acetate 5/95 v/v mixture), 1.4 g of the expected compound 7 (yield 23%) was obtained in the form of a colorless syrup.

[0355] .sup.1H NMR (CDCl.sub.3, 300 MHz): δ (ppm) 9.91 (s, 1 H, NCHN); 7.40 (s, 1 H, NCH); 4.22 (m, 2 H, NCH.sub.2); 3.64 (s, 3 H, OCH.sub.3); 2.94 (t, 2 H, J=7.2 Hz, CH.sub.2); 2.76 (t, 2 H, J=6.9 Hz, CH.sub.2); 1.94 (m, 2 H, CH.sub.2CH.sub.3); 0.95 (m, 3 H, CH.sub.3CH.sub.2)

[0356] .sup.13C NMR (CDCl.sub.3, 75 MHz): δ (ppm) 171.7 (CO); 135.9 (NCHN); 133.9 (Cq); 119.4 (NCH); 52.2 (OCH.sub.3); 48.7 (NCH.sub.2); 31.8 (CH.sub.2); 23.5 (CH.sub.2CH.sub.3); 19.0 (CH.sub.2); 10.8 (CH.sub.3CH.sub.2).

[0357] Molecular mass calculated for C.sub.10H.sub.16N.sub.2O.sub.2Na.sup.+: 219 g/mol; found 219 g/mol.

[0358] 2) Second Stage: Synthesis of 4-(3-Methoxy-3-Oxopropyl)-1-Methyl-3-Propyl-1H-Imidazol-3-Ium Iodide (Compound 8)

[0359] A solution of 1.4 g (7.4 mmol) of the compound 7 obtained above in the preceding stage, of 2.0 g (14.9 mmol) of potassium carbonate and of 1.38 ml (22 3 mmol) of potassium iodide in 100 ml of acetone was maintained at 70° C. under stirring for 2 hours. After cooling to ambient temperature, the reaction mixture was filtered and the solvent was removed under reduced pressure.

[0360] After flash chromatography through silica gel (eluent 100% ethyl acetate and then a methanol/ethyl acetate 5/95 v/v mixture), 931 mg of the expected compound 8 were obtained in the form of a slightly orange-colored syrup (yield 37%).

[0361] .sup.1H NMR (CD.sub.3OD, 300 MHz): δ (ppm) 8.95 (s, 1 H, NCHN); 7.50 (s, 1 H, NCH); 4.18 (t, 2 H, J=7.2 Hz, NCH.sub.2); 3.90 (s, 3 H, NCH.sub.3); 3.73 (s, 3 H, OCH.sub.3); 3.04 (t, 2 H, J=7.0 Hz, CH.sub.2); 2.83 (t, 2 H, J=7.0 Hz, CH.sub.2); 1.95 (q, 2 H, J=3.9 Hz; CH.sub.2CH.sub.3); 1.00 (m, 3 H, J=7.5 Hz, CH.sub.3CH.sub.2)

[0362] .sup.13C NMR (CD.sub.3OD, 75 MHz): δ (ppm) 172.4 (CO); 135.9 (NCHN); 135.1 (Cq); 119.2 (NCH); 51.1 (OCH.sub.3); 50.9 (NCH.sub.2); 32.9 (NCH.sub.3); 31.0 (CH.sub.2); 23.0 (CH.sub.2CH.sub.3); 18.4 (CH.sub.2); 9.6 (CH.sub.3CH.sub.2).

[0363] Molar mass calculated for C.sub.11H.sub.19N.sub.2O.sub.2.sup.+: 211 g/mol; found 211 g/mol.

Example 9

Preparation of Dye-Sensitized Photovoltaic Conversion Cells and Studies of their Properties

[0364] The compound 3a as prepared above was subsequently used in the preparation of a dye-sensitized photovoltaic cell in accordance with the invention (PC1). By way of comparison, a photovoltaic cell not forming part of the invention was also prepared by using DMII as electrolyte salt (PC2).

[0365] The general protocol for the preparation of the PC1 and PC2 cells was as follows:

[0366] Electrolyte Compositions:

[0367] The following electrolyte composition E1 in accordance with the invention was prepared: [0368] Compound 3a: 1 mol/l; [0369] Molecular iodine: 0.15 mol/l; [0370] N-Butylbenzimidazole: 0.5 mol/l; [0371] Guanidinium thiocyanate: 0.1 mol/l; [0372] 3-Methoxypropionitrile: q.s.

[0373] By way of comparison, an electrolyte composition E2 not forming part of the invention, with the following composition, was prepared: [0374] DMII: 1 mol/l; [0375] Molecular iodine: 0.15 mol/l; [0376] N-Butylbenzimidazole: 0.5 mol/l; [0377] Guanidinium thiocyanate: 0.1 mol/l; [0378] 3-Methoxypropionitrile: q.s.

[0379] Preparation of the Photoanode:

[0380] An 8 μm layer of titanium dioxide nanoparticles (diameter 20 nm) was applied by screen printing to a sheet of glass (20×14 mm) covered beforehand with a 300 nm FTO layer.

[0381] A layer of the RuLL′(ANCS).sub.2 complex having a thickness of approximately 2 nm was subsequently deposited on the FTO layer by dip coating.

[0382] Counterelectrode

[0383] A layer of platinum nanoparticles was deposited on the counterelectrode either by cathode sputtering starting from a Pt target or else by evaporation of a solution of a platinum precursor (drop casting) by carrying out the thermal decomposition at 450° C. under air of one or more drops of a 40 mmol/l solution of H.sub.2PtCl.sub.6 in ethanol or alternatively in isopropanol deposited on the surface of the electrode.

[0384] Assembling of the Photovoltaic Cells

[0385] Photovoltaic cells PC1 in accordance with the invention and PC2 not forming part of the invention were subsequently assembled by using respectively the electrolyte compositions E1 and E2, in the following way:

[0386] A conical hole with a diameter of less than 200 μm was made on the counterelectrode by micro-sandblasting, in order to make possible the injection of the electrolyte into the cell. The photoelectrode and the counterelectrode were assembled using a hot-melt polymer seal of the Surlyn® or Bynel® produced and sold by DuPont. The cell was sealed at a temperature of 130° C. for approximately 5 seconds. The electrolyte was injected by capillary action under high vacuum. The external part of the microcone was finally blocked by a glass strip heat-sealed with a polymer of Surlyn® or Bynel® type using a soldering iron tip. The welding was carried out under ultrasound starting from a gallium and indium eutectic in order to obtain an excellent electrical contact.

[0387] These different cells were subsequently tested in photovoltaic conversion under AM 1.5 (Air Mass 1.5 Global) illumination of a class-3A solar radiation simulator (Newport) equipped with a 450 W Xenon lamp. The measurements were carried out with an Oriel PVIV 3A station coupled to a Keithley 2420 SourceMeter.

[0388] The standard surface area of the electrodes was between 0.16 cm.sup.2 and 0.36 cm.sup.2 and the incident surface power was 100 mW/cm.sup.2.

[0389] The density of the current (in mA/cm.sup.2) as a function of the photovoltage (in V) is compared in the appended FIG. 3 for each of the cells PC1 and PC2. In this figure, the dotted-line curve corresponds to a PC2 cell not forming part of the invention and the continuous-line curve corresponds to a PC1 cell in accordance with the invention.

[0390] These results show that, in addition to being a priori more stable chemically and with regard to the Pt interface, the replacement of DMII by the component 3a makes it possible to improve the light/electricity conversion efficiencies, this being because the latter change from 8.0% to 8.5%. The main improvement by virtue of the use of the compound 3a originates from the generation of more photocurrent, the latter changing from 16.9 mA/cm.sup.2 to 19.5 mA/cm.sup.2 (FIG. 3). On the other hand, the photovoltage changes from 680 mV to 647 mV and the fill factor from 69.3% to 67%. This decrease is largely compensated for by the gain in current, which reaches more than 15%.

[0391] The stability of the PC1 and PC2 cells was also studied under conditions of accelerated aging at 70° C., with an incident surface light power at 100 mW/cm.sup.2 and in the absence of UV filters.

[0392] The results obtained are given in the appended FIG. 4. In particular, FIG. 4a gives the results of the change in the photovoltage (in V) as a function of the aging time (in hours), FIG. 4b gives the results of the change in the photocurrent (in mA/cm.sup.2) as a function of the aging time (in hours), FIG. 4c gives the results of the change in the fill factor (FF, in %) as a function of the aging time (in hours) and FIG. 4d gives the results of the change in the light/electricity conversion efficiency (in %) as a function of the aging time (in hours). In these figures, the curves with the solid circles correspond to a PC2 cell not forming part of the invention and the curves with the solid squares correspond to a PC1 cell in accordance with the invention.

[0393] These results show that the conversion efficiency of the PC2 cell not forming part of the invention falls fairly substantially, in particular after aging for 500 hours. This fall in efficiency is mainly related to a significant loss in the photocurrent and in the fill factor. On the other hand, in the case of a PC1 cell in accordance with the invention, the use of the compound 3a as electrolyte salt in the electrolyte composition makes it possible to maintain the photocurrent at high and very stable values. It also makes it possible to achieve better maintenance of the fill factor under the conditions of accelerated aging. Thus, it is observed that the use of the compound 3a makes it possible to maintain a satisfactory conversion efficiency with a loss of efficiency of only 25% in the case of the compound 3a, against 85% in the case of the DMII, after a duration of aging of 1000 hours. FIG. 5 gives the results of the comparison between a PC1 cell and a PC2 cell under the standard conditions of the IEC 61646 protocol, that is to say at 60° C. under 100 mW.cm.sup.−2 (UV filter at 340 nm). In this figure, the light/electricity conversion efficiency (in %) is a function of the aging time (in hours); the solid-line curves correspond to the results of PC1 cells in accordance with the invention and the noncontinuous-line curves correspond to the results of PC2 cells not forming part of the invention. The results given by FIG. 5 also show the superiority of the compound 3a both as regards the efficiencies and the stability over 2000 hours of aging. The four cells assembled with E1 (PC1 cells) have an efficiency retention of the order of 82 to 85%, i.e. greater than the 80% required by the standard IEC 61646 protocol and far beyond the 1000 hours of accelerated aging recommended by the protocol. In contrast, the four cells assembled with E2 (PC2 cells not in accordance with the invention) show a more pronounced decline in the efficiency during aging. One of the four cells had an efficiency of less than 2% after 600 hours (not given) and the other three show a retention of 77%, 66% and 53% after aging for 1700 hours, i.e. values far lower than those observed with the PC1 cells and lower than the bar of 80% of the IEC 61646 protocol.

[0394] Finally, FIG. 6 gives the results obtained with the PC1 and PC2 cells during an aging test at very low temperature (−40° C. in the dark). In this figure, the light/electricity conversion efficiency (in %) is a function of the aging time (in hours); the solid-line curve corresponds to the results of PC1 cells in accordance with the invention and the noncontinuous-line curve corresponds to the results of PC2 cells not forming part of the invention. These results show that El is also very effective under such conditions of use. The use of this electrolyte shows a retention after 1000 hours of 99.2% against 96.2% for E2. The efficiencies after 1000 hours at −40° C. are 8.48% for E1 and 7.51% for E2.

Example 10

Preparation of Dye-Sensitized Photovoltaic Conversion Cells and Studies of their Properties with Compounds of Formula (I) in Accordance with the Invention of the 3 Series with R.SUB.1.=CH.SUB.3., R.SUB.3.=H and R.SUB.2.=R.SUB.4.=C.SUB.n.H.SUB.2n+1 .(1≦n≦6) (i.e., the compounds 3a to 3f) and R.SUB.1.=C.SUB.2.H.SUB.5., R.SUB.3.=H and R.SUB.2.=R.SUB.4.=CH.SUB.3 .(Compound 6)

[0395] Dye-sensitized photovoltaic cells were prepared using the compounds of the 3 series (compounds 3a to 3f) as prepared in examples 1 to 6 above and also the compound 6 as prepared in example 7, furthermore using, for the composition of the electrolyte, the same ingredients as in electrolyte E1 as prepared in example 9. The preparation of the photoanode and of the counterelectrode and the cell assembling were subsequently carried out in the same way as in example 9 above.

[0396] The cells thus prepared were tested under conditions of accelerated aging at 60° C. under 100 mW.cm.sup.−2 of incident light filtered against UV radiation with a wavelength of less than 340 nm. The results obtained are given by the appended FIG. 7, in which the current density (in mA/cm.sup.2) is a function of the aging time (in hours). These results show that, a priori, the compounds of the 3 series are always very stable under these aging conditions since, after aging for 1000 hours, the retention of the efficiency is between 81% for the hexyl chain (compound 3d) and 89% for the methyl chain (compound 3a) and the propyl chain (compound 3c). Furthermore, the results appear to indicate that the propyl chain is the most stable. The series shows that, the longer the alkyl chain, the greater its solubility in the medium under consideration. On the other hand, the results appear to indicate that the conversion efficiency varies as a function of the length of the chain. The lengthening of the ester chain also slightly decreases the conversion efficiency but does not affect the stability, which remains noteworthy, much better than that of the state of the art (PC2). The compounds of the 3 series also show just as good a stability at low temperature of −40° C., analogous to the results obtained in the preceding example.