Method for functionalizing a solid substrate, other than a substrate made of gold, via specific chemical compounds

Abstract

The invention relates to a method for functionalizing an electrically conductive substrate, which is not a substrate made of gold, via a layer of chemical compounds, said method comprising the following steps: a step in which the electrically conductive substrate is placed in contact with chemical compounds comprising at least a disulfide terminal group; a step in which the disulfide terminal group of said chemical compounds is electro-oxidized, causing said chemical compounds to form a layer at the surface of the electrically conductive substrate.

Claims

1. A method for functionalizing an electrically conductive substrate via a layer comprising a chemical compound, the substrate being a substrate made of a material selected from the group consisting of carbon, platinum, an indium-tin oxide and nickel, comprising: contacting the electrically conductive substrate with a chemical compound comprising at least a disulfide terminal group, said chemical compound satisfies formula (I): ##STR00019## wherein: X is a charge storage group, which is a polyazacycloalkane group complexed with at least a metal element, said polyazacycloalkane group being a tetrazacycloalkane group selected from the group consisting of formula (II), formula (III) and formula (IV): ##STR00020## wherein: R.sup.1, R.sup.2, R.sup.3 and R.sup.4 represent, independently of each other, an alkyl, aryl, alkylaryl group, a halogen atom, an (alkyl)metallocene group, wherein the alkyl, aryl, alkylaryl, (alkyl)metallocene group may be perfluorinated; M is a metal element having at least two degrees of oxidation; braces indicating the spot through which said tetraazacycloalkane group is bound to the disulfide group via a spacer group; L is a single bond or an organic spacer group; Z is a cyclic disulfide group; and n is a whole number ranging from 1 to 6; and electro-oxidizing the cyclic disulfide terminal group of said chemical compounds, causing said chemical compounds to form a layer at the surface of the electrically conductive substrate.

2. The method of claim 1, wherein the tetraazacycloalkane group is of formula (II).

3. The method of claim 1, wherein the tetraazacycloalkane group satisfies one of formula (V) and formula (VI): ##STR00021## wherein: M is a metal element having at least two degrees of oxidation; and T represents a ferrocene group.

4. The method of claim 1, wherein the metal element is a transition metal element.

5. The method of claim 4, wherein the transition metal element is selected from the group consisting of Cr, Mn, Fe, Co, Ni, and Cu.

6. The method of claim 1, wherein the metal element is copper.

7. The method of claim 1, wherein said charge storage group and said disulfide terminal group are separated by an organic spacer group which is a hydrocarbon group, being in the form of a linear or branched chain, in which one or more bonding groups can be inserted.

8. The method of claim 7, wherein the hydrocarbon group is an alkylene group, in which one or more bonding groups can be inserted.

9. The method of claim 7, wherein the one or more bonding groups are selected from the group consisting of a (CO) group, a (CO)O group, a SO.sub.2 group, and an amide group.

10. The method of claim 1, wherein said charge storage group and said disulfide terminal group are separated by an organic spacer group satisfying the following fomula (VII):
(CH.sub.2).sub.4NHCO(CH.sub.2).sub.4(VII).

11. The method of claim 1, wherein the disulfide group is a group of following formula (VIII): ##STR00022##

12. The method of claim 1, wherein the chemical compounds satisfy one of formula (IX) and formula (X): ##STR00023## wherein T represents a ferrocene group.

13. The method of claim 1, wherein the tetraazacycloalkane group is of formula (III).

14. The method of claim 1, wherein the tetraazacycloalkane group is of formula (IV).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 represents a specific configuration of a capacitive charge storage device according to the invention.

(2) FIG. 2 represents a voltamperogram obtained within the scope of example 2.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

(3) In this part will be illustrated: the preparation of a specific organic compound comprising a disulfide terminal group (Example 1); the functionalization of an electrode made of vitreous carbon by this compound and the study of the system obtained by voltammogram (Example 2).

EXAMPLE 1

(4) This example illustrates the preparation of a compound of following formula (XI):

(5) ##STR00013##
which takes place in three steps: the synthesis of 1,4,8,11-tetraazatricyclo[9,3,1,1]hexadecane of following formula (XII):

(6) ##STR00014## from the compound of formula (XII), the synthesis of the iodide salt of methyl-4,11-diazoniatricyclo[9,3,1,1]hexadecane of following formula (XIII):

(7) ##STR00015## from the compound of formula (XIII), the synthesis of (propan-3-nitrile)-4,8,11-trimethyl-1,4,8,11-tetraazacyclotetradecane of following formula (XIV):

(8) ##STR00016## from the compound of formula (XIV), the synthesis of (butan-4-amine)-4,8,11-trimethyl-1,4,8,11-tetraazacyclotetradecane of following formula (XV):

(9) ##STR00017## from the compound of formula (XV), the synthesis of the compound of formula (XVI) mentioned above.
a) Synthesis of the Compound of Formula (XII)

(10) Two equivalents of formaldehyde (0.9 mL; 37% in water) are added rapidly to an aqueous solution of cyclame (1 g; 1.07 mmoles in 60 mL) at 0 C. The mixture obtained is placed under stirring for 2 hours, whereby a white precipitate forms, which is then filtered, washed with water and dried under reduced pressure. The white powder obtained is used without purification.

(11) The yield is 96%.

(12) The .sup.1H NMR and .sup.13C NMR results confirm the compound of formula (XII) is obtained.

(13) b) Synthesis of the Compound of Formula (XIII)

(14) 600 mg of the compound of formula (XII) are dissolved in 70 mL of dry diethyl ether. After 20 minutes of bubbling under argon, 10 mL of a solution of diethyl ether containing 75 L of iodomethane (2.8 mmoles; 1.05 equivalents) is added slowly. After 24 hours under vigorous stirring in darkness, a white precipitate forms, which is then filtered and washed with 2*40 mL of diethyl ether. The white powder obtained is then dissolved in 100 mL of chloroform, the solution being filtered to eliminate impurities. The solution is evaporated under vacuum, leaving a colourless oil remaining, which crystallizes slowly in the form of white platelets. The yield is 85%.

(15) The .sup.13C NMR results confirm the compound of formula (XIII) is obtained.

(16) c) Synthesis of the Compound of Formula (XIV)

(17) To a solution of acetonitrile comprising the compound of formula (XIII) (1.47 g; 4 mmoles in 30 mL) is added rapidly an excess of iodobutyronitrile (1.48 g; 7.6 mmoles). The solution obtained is degassed by bubbling with argon and heated to 70 C. for 30 minutes. The temperature is then maintained at 50 C. for 3 days.

(18) A white precipitate is obtained corresponding to a bis-ammonium salt of following formula (XIV):

(19) ##STR00018##

(20) This precipitate is filtered, washed with 2*50 mL of acetonitrile, 50 mL of dichloromethane and 100 mL of diethyl ether and the resulting white powder is dried under reduced pressure (1.43 g).

(21) Starting from the aforementioned compound, the compound of formula (XIV) is obtained in the following manner.

(22) To a methanolic solution of the compound of formula (XIV) under magnetic stirring, is added an excess of sodium borohydride. The resulting mixture is left to react for several hours. The solution is then concentrated under reduced pressure and 50 mL of distilled water are added. The aqueous solution is then extracted with 3*50 mL of chloroform. The organic phases are combined, dried over MgSO.sub.4, evaporated and dried under reduced pressure, whereby a colourless oily residue is obtained.

(23) The .sup.1H NMR and .sup.13C NMR results confirm the compound of formula (XIV) is obtained.

(24) d) Synthesis of the Compound of Formula (XV)

(25) To an ethanolic solution of compound of formula (XIV) under stirring (0.3 g; 0.97 mmoles in 60 mL), is added rapidly sodium hydroxide (90 mg; 2.21 mmoles). To this mixture under stirring is added, alternatively and by small fractions, hydrazine monohydrate (700 L; 13 mmoles; 15-20 equivalents) and Raney nickel in ethanol (0.4 g in 10 mL). The mixture is left to react for 24 hours then filtered on a Millipore filter. The filtrate is evaporated and the residue is dissolved in a minimal volume of toluene. The solution is filtered to eliminate the excess of sodium hydroxide. The filtrate is evaporated and dried under reduced pressure, whereby a colourless oily residue (Yield: 0.279 g; 92%) is obtained.

(26) The .sup.1H NMR and .sup.13C NMR results confirm the compound of formula (XV) is obtained.

(27) e) Synthesis of the Compound of Formula (XI)

(28) To a solution under stirring comprising anhydrous dichloromethane and D,L-lipoic acid (200 mg; 0.96 mmoles in 30 mL), degassed beforehand with argon and cooled to 0 C., is added a solution of (2-(1H-7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate methanaminium (0.366 g; 0.96 mmoles) dissolved in 2 mL of anhydrous dimethylformamide. Distilled triethylamine (400 L; 2.88 mmoles) is then added and the mixture is stirred for 15 minutes at ambient temperature. The solution is cooled to 0 C. and a solution comprising anhydrous dichloromethane and the compound of formula (XV) (278 mg; 0.886 mmoles in 35 mL) is added drop by drop. The mixture obtained is then left under stirring at ambient temperature for 24 hours. The solvents are evaporated under reduced pressure and the oily residue obtained is purified by column chromatography (neutral alumina, deactivated with an ethyl acetate/water/methanol (150/1/20) mixture) with pure ethyl acetate as starting elution solvent then increasing quantities of methanol (5-20%) during the elution. The main fraction is evaporated up to dryness and the colourless oily residue obtained is dried under reduced pressure (Yield: 0.365 g; 82%).

(29) The .sup.13C NMR results confirm the compound of formula (XI) is obtained.

EXAMPLE 2

(30) In this example is illustrated the functionalization of a vitreous carbon electrode.

(31) Prior to this functionalization, the preparation is carried out of a copper complex of formula (IX) defined above obtained from the compound prepared according to example 1 in the manner described below.

(32) To a solution of the compound (XI) (50 mg; 9.97*10.sup.5 moles) dissolved in 15 mL of methanol are added, under stirring and at ambient temperature, 32.6 mg of Cu(BF.sub.4).sub.2.6H.sub.2O (9.47*10.sup.5 moles; 0.95 equivalents) dissolved beforehand in 5 mL of methanol. After 30 minutes of stirring, the solvent is evaporated under reduced pressure then the evaporation residue is washed with 2*10 mL of cold methanol then 50 mL of diethyl ether. The residue is then again dissolved in 5 mL of acetonitrile then precipitated by addition of 30 mL of diethyl ether and filtered. A hygroscopic blue powder is obtained and is dried under vacuum. The complex is obtained with a yield of around 80%.

(33) To functionalize the vitreous carbon electrode, it is immersed in a solution comprising the copper complex of formula (IX), the preparation method of which is described above, said complex being present at a concentration of 1 mM in acetonitrile, and is then subjected to a step of cycling between 0.2 to +1 V/AgAg.sup.+ (10.sup.2 M in acetonitrile) at a scanning speed of 100 mV.Math.s.sup.1, the number of cycles carried out being 5.

(34) The electrochemical assembly used is an assembly with three electrodes with an organic electrolyte comprising: a reference electrode consisting of a solid silver wire placed in contact with a solution of AgNO.sub.3 (10.sup.2 M) in acetonitrile; a working electrode consisting of a vitreous carbon disc of 3 mm diameter; a counter electrode consisting of a platinum wire; and an electrolyte consisting of acetonitrile containing tetrabutylammonium perchlorate (0.1 M) and the copper complex of formula (IX) (1 mM).

(35) Following this functionalization and after rinsing with acetonitrile, the electrode thereby modified is subjected to a cyclic voltamperometry experiment consisting in subjecting the substrate thereby coated to successive cycles (150 in number) between 1 V and +0.1 V with respect to Ag/Ag.sup.+ (10.sup.2 M) at a rate of 50 V.Math.s.sup.1.

(36) The assembly used comprises: a reference electrode consisting of a solid silver wire placed in contact with a solution of AgNO.sub.3 (10.sup.2M) in acetonitrile; a working electrode consisting of the coated substrate; a counter electrode consisting of a platinum wire; and an electrolyte consisting of acetonitrile containing tetrabutylammonium perchlorate (0.1 M).

(37) The voltammogram obtained is represented in appended FIG. 2.

(38) For the cycle 1 indicated in the figure, a reversible redox system (centred around 0.7 V) may be noted attributed to the redox system of Cu.sup.II for the compound grafted in a diastereoisomeric configuration of type I, corresponding to the diastereoisomer RSRS.

(39) As the cycles proceed, this redox system disappears to the benefit of a new reversible redox system (centred around 0.25 V) attributable to the redox system of Cu.sup.II for the compound grafted in a diastereoisomeric configuration of type V (corresponding to the diastereoisomer RRRR), as is illustrated for the cycle 150 represented in the same FIG. 2.

(40) This indicates, without ambiguity, that the electron transfer reactions of the complex immobilised on a surface are coupled to chemical reactions and that the passage from one state to the other is realised. The two stable forms of the switch have oxido-reduction potentials separated by 500 mV, which attests to a stabilisation of the different redox states.

(41) With a view to storage of information, the fact of being able to identify the two isomers (type I and type V) at a high scanning speed signifies that it is possible to read the corresponding two items of information without too much loss of information. In other words, it is possible to read the information (0 or 1) without transforming the 0 into 1 and vice versa.