EP1695076A2 - Reactive oxygen detecting and/or absorbing compound, method for preparing said compound and a device comprising it - Google Patents

Abstract

The inventive reactive oxygen detecting and/or absorbing compound is characterised in that it consists of a complex molecular metallic (1)/ ligand (2) derivatives which changes the colour thereof according to the oxydation degree of a metal and is connected to the surface of a solid support (3) by a covalent bond.

Description

“Reactive compound detector and / or oxygen absorber, process for preparing such a compound as well as device containing it” The present invention relates to a reactive compound capable of having two complementary functions, namely on the one hand detecting the presence of oxygen by a clear color change, visible to the naked eye as with a spectrophotometer, and on the other hand chemically and irreversibly absorb the oxygen contained in a closed enclosure. Oxygen indicator systems have been extensively described in the literature; they generally use a dye which changes color according to its oxidation level associated with a reducing agent to maintain the reduced form of the dye in the absence of oxygen (documents DE-30 25 264, JP-62 183 834, WO -93/24820, WO- 98/03866 ...). The oxygen indicator reagent can be in the form of ink (documents DE-30 25 264, JP-62 183 834), included in a thermoplastic (document WO-2003/00557), packed between materials permeable to oxygen (document WO-93/24820) or even included in an amorphous medium (document FR-2 710 751). Specialists have at the same time already proposed a wide range of oxygen-absorbing devices which are used in many fields of technology, among which, by way of example, mention may be made of the food industry, in particular for the production of packaging allowing the preservation of foods under an inert atmosphere, the pharmaceutical industry, for the preservation of preparations for medical use, or more generally all areas requiring an atmosphere devoid of oxygen or with a low oxygen content. These different systems have one drawback in common, linked to the fact that the indicator and / or absorber reagent is subject to migration phenomena, which can be very annoying, in particular in the context of applications related to the food industry or pharmaceutical. In this context, the object of the present invention is to provide a reactive detector and / or oxygen-absorbing compound in which the indicator reagent is irreversibly linked to a solid support, so that it is not liable to be exposed migration phenomena and also obtainable from non-toxic products available commercially. This reactive compound is characterized in that it consists of a metallic derivative / ligand color changing complex depending on the degree of oxidation of the metal and connected to the surface of a solid support by a covalent bond. Given the fact that the active molecules of the reactive compound according to the invention are fixed on a support, thus constituting a hybrid material, these cannot migrate by contact with another substance. According to the invention, the molecular complex is preferably linked to the surface of the support via a derivative of an organic link chain. Such a chain contains on the one hand a first grafting function or function allowing its attachment to the support, and on the other hand a second coordinating function or function adapted to achieve coupling with a molecular entity of condensation associated to form the ligand which allows the complexation of the metal derivative. The attached figure is an illustrative diagram of the configuration of the reactive compound according to the invention and of its color change following a chemical reaction of the metallic derivative which it contains with oxygen. Such a reactive compound is constituted by a complex of metallic derivative 1 / ligand 2 connected to the surface of a support 3 via a derivative of an organic linking chain 4 which in fact constitutes an arm making it possible to fix the functional part 1, 2 of the reactive compound with the support 3. The reactive compound according to the invention therefore consists of an organic molecular complex sensitive to oxygen firmly attached by covalent chemical bonds to the surface of a support which retains its mechanical properties but takes on the color of this complex, this color being modified when it is exposed to an atmosphere containing oxygen. The speed of this color change depends on the temperature as well as the partial oxygen pressure and the humidity of the atmosphere considered. Used alone or in combination with other oxygen absorbers, this reactive compound makes it possible to detect the presence of oxygen and to absorb the oxygen present in an enclosure. According to the invention, the ligand may advantageously include a heteroatomic chain, optionally substituted, containing two conjugated functional groups and in which at least two nitrogen atoms, one of which belongs to a pyridine ring or the like, are separated by two atoms. carbon. According to the invention, a nucleus analogous to a pyridine nucleus can, for example, be a substituted pyridine nucleus or a polycyclic system containing at least one pyridine nucleus. According to a preferred characteristic of the invention, the coordination function of the organic link chain is an amine function, in particular a primary amine function. The molecular entity of condensation can advantageously consist of 2-pyridine carboxaldehyde, 2-pyridine carboxylic acid or its chloride. According to this characteristic, the ligand therefore consists of a compound resulting from the condensation of 2-pyridine carboxaldehyde, or 2-pyridine carboxylic acid or its chloride with the amino function of the organic link chain. Such condensation can indeed lead to the formation of bidentate, tridentate or tetradentate nitrogen ligands capable of complexing many transition metals and their derivatives. Such complexes can, in the presence of oxygen, take on an intense color characteristic of the degree of oxidation of the metal. According to the invention, the metal derivative must be chosen so that within it, the metal is in a low degree of oxidation and is thus capable of reacting with oxygen. By way of example, this metal derivative can advantageously be chosen from the group formed by CuCl, [Cu (CH3CN) 4] [PFβ], AgNO ₃ , and FeSO ₄ . In the metal derivative [Cu (CH3CN) 4] [PFβ] the counter anion

PFβ can be replaced by any other weakly coordinating counter anion such as BF ₄ or CF ₃ OSO ₂ . According to a first variant of the invention, the support is an organic polymer support such as polystyrene beads or of a copolymer based on polystyrene and the grafting function of the organic link chain is an alkene function. By way of example, the reactions below constitute three examples of preparation of ligands L1, L2, L3 from organic chains. commercially available binding ques, and containing on the one hand an alkene function allowing their fixation on an organic polymer support by copolymerization and on the other hand a primary amine function capable of reacting by condensation with 2-pyridine carboxaldehyde or the 2-pyridine carboxylic acid. The molecular complexes obtained after reaction of the ligand with a derivative of a transition metal have an intense metal-ligand absorption band in the visible region. The color of this strip is often characteristic of the degree of oxidation of the metal.

Furthermore, functional polystyrene beads having one or more primary amine functions and / or one or more secondary amine functions which are commercially available can constitute an easy-to-use support. According to a second variant of the invention, the support is an inorganic support such as beads from an inorganic glass and the grafting function of the organic linking chain is a trialkoxysilane function, in particular trimethoxysilane. The support is preferably constituted by an activated metal oxide such as Tiθ2, ZrO ₂ , or preferably Siθ2 or AI2O3 which correspond to inexpensive oxides, completely free of toxicity and also available commercially under a wide range of quality. Such a support can advantageously be in the form of vitreous beads which may have different particle sizes θ for example 60 <θ <200 μm or 200 <θ <500 μm. According to this variant of the invention, the organic linking chain can be advantageously chosen from the group formed by 3-aminopropyltrimethoxysilane, N- [3- (trimethoxysilyl) - propoyl] ethylene-diarnine and 3- (2- ( 2-ammo) ethylammo] propyl-trimethoxy-silane The invention also relates to a process for the preparation of a reactive compound of the above-mentioned type linked to the surface of an inorganic support. process is characterized in that it comprises the following stages:

- activation of the support by soaking in an acid solution, washing and air drying,

- grafting of the organic link chain on the activated support by soaking in ethanol at room temperature,

- in situ synthesis of the ligand by adding the molecular entity of condensation to the organic chain previously grafted onto the support, activated or not, at room temperature and in ethanol medium, and

- coordination of the metal derivative on the ligand or metallation by soaking in an ethanol solution at room temperature under an inert atmosphere. It should be noted that the steps of grafting the organic chain of binding onto the activated support and of in situ synthesis of the ligand are in fact inseparable and can be carried out in one direction or the other, which means that the activated support can be introduced into the reaction medium before or after the molecular entity of condensation. The process according to the invention has the advantage of being able to be carried out in air, with the exception of the last metallation step which requires an inert atmosphere, although the reactive compound finally obtained is intended for react with oxygen. In the exemplary embodiment in which the support consists of silica beads and the organic chain by 3-aminopropyl trimethoxysilane, the grafting of the organic link chain on the activated support and the in situ synthesis of the ligand can be schematized as below :

The process according to the invention thus makes it possible to obtain an Si-1 chain grafted onto the support, then, after addition of 2-pyridinecarboxaldehyde and stirring using an ultrasonic bath (sonication), an Si compound -2 consisting of the ligand grafted on the support activated by a derivative of the organic chain. In the case of a metallic derivative MLn, the final metallation step can be shown diagrammatically as below.

The compounds Si-3 and Si-4 represented below correspond to other examples of structures of grafted complexes in accordance with the invention obtained from organic chains constituted by N- [3- (trim.ethoxysilyl) propoyl] ethylenediamine or 3- [2- (2-amino) ethylammo] propyl-trimethoxysilane.

The different steps of the process according to the invention will be illustrated in more detail by the following examples. Example 1: Activation of the support. 50 g (0.238 mol) of ammonium persulfate are gradually introduced into a Erlenmeyer flask containing one liter of 10 N sulfuric acid, with magnetic stirring. This solution once cooled to 20 ° C is poured into a beaker containing 250 g of silica. After homogenization the silica is left to soak for one hour. After filtration through a bϋchner, the silica is rinsed 5 times with 100 ml of water and then 5 times with 100 ml of distilled water. The silica thus activated is dried under vacuum at 20 ° C for 30 minutes minimum, then at 120 ° C in an oven for 3 hours. Example 2: Grafting reaction: preparation of Si-2. In a beaker, 3-ammopropyltrimethoxysilane (186.5 μl, 1 mmol) is dissolved in an excess of ethanol (30 ml), then 1 g of activated fine silica is introduced directly into the reaction medium. The solution is left to stand at 20 ° C for one hour. An equivalent of 2-pyridine carboxaldehyde (96.5 μl, 1 mmol) is then added to the solution and the reaction mixture is stirred using an ultrasound bath for 30 minutes. Finally, the support is recovered by filtration on a bϋchner and rinsed with ethanol (3 times 20 ml) then with ether (3 times 20 ml). The grafted silica is left to dry under vacuum for 15 minutes at 20 ° C. Grafting rate: 0.82 mmol / g. Example 3: Grafting reaction: preparation of Si-2. In a beaker, 2-pyridine carboxaldehyde (96.5 μl, 1 mmol) is dissolved in ethanol (30 ml), then an equivalent of 3-ammo-5-pyriάL ^ etrimethoxysilane (136.5 μl, (1 mmol) is added to the solution and the reaction mixture is left under stirring for 30 minutes. The support is then introduced directly into the dream environment. Two techniques were then used: => Either the mixture is left to stand for 18 hours at 20 ° C (soaking method). => Either the mixture ^" is stirred using an ultrasonic bath for 30 minutes at 20 ° C. After grafting, the support is filtered, rinsed with ethanol (3 times 20 ml) and then with ether (3 times 20 ml). It is finally dried in the open air for 30 minutes. It should be noted that the initially white beads take after grafting, a yellowish hue, characteristic of imine, appears. Grafting rate: 0.79 mmol / g Example 4: Metallation reaction of Si-2. In a Schlenk tube, at 20 ° C, the grafted ligand (1 g) is suspended in deaerated ethanol (30 ml), then CuCl (99 mg, 1 mmol) is introduced under a stream of argon. The mixture is maintained for 15 minutes with magnetic stirring. After filtration and washing with ethanol (3 times 10 ml), the support is isolated and dried under vacuum (2 h 30 min, 20 ° C) then conditioned under an inert atmosphere. Metallation rate: 0.76 mmol / g Example 5: Metallation reaction of Si-2. In a Schlenk tube, at 20 ° C, the grafted ligand (0.200 g) is suspended in deaerated ethanol (10 ml), then [Cu (CH3CN) ₄ ] [PFβ] (0.074 g, 0.2 mmole) is introduced under a stream of argon. The mixture is maintained for 15 minutes with magnetic stirring. After filtration and washing with ethanol (3 times 10 ml), the support is isolated and dried under vacuum (2 h 30 min, 20 ° C) then conditioned under an inert atmosphere. Metallation rate: 0.80 mmol / g Example 6: Metallation reaction of Si-2. In a Schlenk tube, at 20 ° C, the grafted ligand (0.200 g) is suspended in a deaerated water / ethanol mixture (50:50, 20 ml), then FeSOt (0.056 g, 0.2 mmol) is introduced under a stream of argon. The mixture is maintained for 15 minutes with magnetic stirring. After filtration and washing with ethanol (3 times 20 ml), the support is isolated and dried under vacuum (2 h 30 min, 20 ° C) then conditioned under an inert atmosphere. Metallation rate: not determined. Example 7: Metallation reaction of Si-2. In a Schlenk tube, at 20 ° C, the grafted ligand (0.200 g) is suspended in deaerated ethanol (20 ml), then AgNθ3 (0.339 g, 0.2 mmol) is introduced under a stream of argon . The mixture is maintained for 15 minutes with magnetic stirring. After filtration and washing with ethanol (3 times 20 ml), the support is isolated and dried under vacuum (2 h 30 min, 20 ° C) then conditioned under an inert atmosphere. Metallation rate: not determined ^{"~ ~""~'~} Example 8: Grafting reaction: preparation of Si-3. In a beaker, at room temperature, 1.85 ml of N- (3- (trimethylsilyl) -propyl ) ethylenediarxιine is dissolved in an excess of ethanol (approximately 150 ml) then 10 g of activated silica with the mixture is left to stand for an hour. 1 ml of 2-pyridinecarboxaldehyde is added to the solution and the reaction mixture is stirred using an ultrasonic bath for 30 minutes. Finally the support is isolated by filtration on Bϋchner and rinsed with ethanol (3 times 20 ml), then with ether (3 times 20 ml). The grafted silica is dried under vacuum for 15 minutes at 20 ° C. Grafting rate: 0.65 mmol / g. Example 9: Grafting reaction: preparation of Si-4. In a beaker, at 20 ° C., 1.85 ml of 3- [2- (2- amiαoethylammo) ethylaιnino] propyltrirnethoxysilane, 150 ml of ethanol and 10 g of activated silica are successively introduced. The mixture is left to stand for one hour. Then, 1 ml of 2-pyridine-carboxaldehyde is added to the solution and the reaction mixture is stirred using an ultrasonic bath for 30 minutes. Finally, the support is recovered by filtration on Bϋchner and rinsed with ethanol (3 times 20 ml), then with ether (3 times 20 ml). The grafted silica is dried under vacuum for 15 minutes at 20 ° C. Grafting rate: 0.60 mmol / g. Example 10: Metallation reaction of Si-3. In a Schlenck tube, at 20 ° C, the grafted ligand (1 g) is suspended in deaerated ethanol (30 ml), then CuCl (0.100 g) is introduced under a stream of argon. The mixture is kept for 15 minutes under _-. magnetic agitation. After filtration and washing with ethanol (3 times 10 ml), the support is isolated and then dried under vacuum (2 h 30 min, 20 ° C). Metallation rate: 0.80 mmol / g. Example 11: Metallation reaction of Si-3. In a Schlenck tube, at 20 ° C, the grafted ligand (1 g) is suspended in deaerated acetone (10 ml), then 0.373 g of [Cu (CH3CN) ₄ ] [PF6] is introduced under current argon. The mixture is maintained for 15 minutes with magnetic stirring. After filtration and washing with ethanol (3 times 10 ml), the support is isolated and dried under vacuum (2 h 30 min, 20 ° C). Metallation rate: 0.68 mmol / g. Example 12: Metallation reaction of Si-4. In a Schlenck tube, at 20 ° C, the grafted ligand (1 g) is suspended in deaerated ethanol (30 ml), then CuCl (0.100 g) is introduced under a stream of argon. The mixture ^" is maintained for 15 minutes without ^" magnetic stirring. After filtration and washing with ethanol (3 times 10 ml), the support is isolated and dried under vacuum (2 h 30 min, 20 ° C) then conditioned under an inert atmosphere. Metallation rate: 0.80 mmol / g. Example 13: Metallation reaction of Si-4. In a Schlenck tube, at 20 ° C, the grafted ligand (1 g) is suspended in deaerated acetone (10 ml), then 0.373 g of [Cu (CH3CN) ₄ ] [PFβ] are introduced under current argon. The mixture is maintained for 15 minutes with magnetic stirring. After filtration and washing with ethanol (3 times 10 ml), the support is isolated and dried under vacuum (2 h 30 min, 20 ° C). Metallation rate: 0.70 mmol / g.

The present invention also relates to a detector and / or oxygen absorber device containing a reactive compound of the above-mentioned type. Such a device can have various configurations without departing from the scope of the invention and can, for example, consist of printing ink in which the reactive compound is incorporated; one can thus obtain oxychrornic inks which change color in contact with oxygen. Such inks are likely to find applications in particular in the field of marketing or education. This device can also take the form of absorbers and / or indicators of the presence of oxygen in which the reactive compound can be bonded to a support by an adhesive, or an adhesive with controlled melting temperature (holt melt) or still dispersed in a polymer and then extruded, or else integrated in a sachet, in porous systems or between films permeable to oxygen so as to be in the form of a label. This device can also be in the form of packaging sheets which change color when they are brought into contact with an atmosphere containing oxygen gas.

Claims

CLAIMS 1 °) Reactive compound detector and / or oxygen absorber, characterized in that it is constituted by a metallic derivative molecular complex (l) / ligand (2) changing color according to the degree of oxidation of the metal and connected to the surface of a solid support (3) by a covalent bond. 2) reactive compound according to claim 1, characterized in that the molecular complex is linked to the surface of the support by means of a derivative (4) of an organic link chain containing on the one hand a first function or function grafting allowing its attachment to the support, and on the other hand a second function or coordination function suitable for coupling with a molecular entity of condensation associated to form the ligand which allows the complexing of the metal derivative. 3 °) reactive compound according to claim 2, characterized in that the ligand comprises a heteroatomic chain optionally substituted containing two conjugated imine functional groups andin which at least two nitrogen atoms, one of which belongs to a pyridine ring or the like are separated by two carbon atoms. 4 °) Reactive compound according to claim 3, characterized in that the coordination function of the organic link chain is an amino function. > 5 °) Reactive compound according to any one of claims 3 and 4, characterized in that the molecular entity of condensation consists of 2-pyridine carboxaldehyde, or 2-pyridine carboxylic acid or its chloride. 6 °) reactive compound according to any one of claims 1 to 5, characterized in that the metal derivative is chosen from the group formed by CuCl, [Cu (CH ₃ CN) ₄ ] [PF ₆ ], AgNOs, and FeSO ₄ . 7 °) Reactive compound according to any one of claims 1 to 6, characterized in that the support is an organic polymer support such as polystyrene beads or of a copolymer based on polystyrene and the grafting function of the chain organic bonding is an alkene function. 8 °) Reactive compound according to claim 7, characterized in that the beads constituting the support are functional polystyrene beads having one or more primary amine functions and / or one or more secondary amine functions. 9 °) Reactive compound according to any one of claims 1 to 6, characterized in that the support is an inorganic support such as beads of an inorganic glass and the grafting function of the organic linking chain is a trialkoxysilane function in particular trimethoxysilane. 10 °) Reactive compound according to claim 9, characterized in that the organic chain is chosen from the group formed by 3-amino-propyltrimethoxysilane, N- [3- (1riιnethoxysilyl) propoyl] ethylenedediaιnine and 3- [2- (2 amino) ethylamino] propyl-triméthθ3cysilane. 11 °) Reactive compound according to any one of claims 9 and 10, characterized in that the support consists of an activated metal oxide such as Tiθ2, ZrO ₂ , or preferably Siθ2 or AI2O3. 12 °) Process for the preparation of a reactive compound according to any one of Claims 9 to 11, in which the support is an inorganic support, characterized in that it comprises the following steps: - activation of the support by soaking in a ^" solution à cidê, ^" washes then air drying, - grafting of the organic chain on the activated support by soaking in ethanol at room temperature, in situ synthesis of the ligand by addition of the molecular entity of condensation to the organic chain previously grafted onto the support activated or not at room temperature and in ethanol medium, and - coordination of the metal derivative on the ligand by soaking in an ethanol solution at room temperature under an inert atmosphere. 13 °) Detector and / or oxygen absorber device, characterized in that it contains a reactive compound according to any one of claims 1 to 12.