IONIC SCINTILLATORS

Abstract

The invention relates to a compound having one of the following ionic chemical structures (I), R represents an alkyl or O-alkyl group optionally comprising one or more unsaturations, as a linear or branched chain, of 1 to 30 carbon atoms, optionally substituted; R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 represent, independently of one another, an atom or a group of atoms; (Het)aryl independently represents an aryl or heteroaryl group; and A represents an anion.

##STR00001##

Claims

1. A compound having one of the following ionic chemical structures: ##STR00012## R represents an alkyl group or O-alkyl group, alkyl being defined as a saturated hydrocarbon radical, in a linear or branched chain, having 1 to 30 carbon atoms, possibly substituted; R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, and R12 representing independently from each other an atom or group of atoms; (Het)aryl independently represents an aryl or heteroaryl group; and A.sup.? represents an anion.

2. The compound according to claim 1, characterised in that it has the following chemical structure: ##STR00013## where R, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, and R12 are as defined in claim 1.

3. The compound according to claim 1, characterised in that R represents an alkyl group or O-alkyl group, where alkyl is a saturated hydrocarbon radical, in a linear or branched chain, having 5 to 12 carbon atoms.

4. The compound according to claim 1, characterised in that R represents an alkyl group C.sub.nH.sub.2n+1 or OC.sub.nH.sub.2n+1, where n is a number ranging from 1 to 30.

5. The compound according to claim 1, characterised in that R is selected from among the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl, decyl, dodecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, isopropyl, tert-butyl, 2-ethylhexyl, 2-methylbutyl, 2-methylpentyl, 1-methylpentyl and 3-methylheptyl radicals.

6. The compound according to claim 1, characterised in that R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, and R12 represent independently of one another: H, F, Cl, Br, I, a C.sub.1-C.sub.30 alkyl, a C.sub.3-C.sub.7 cycloalkyl, a C.sub.6-C.sub.10 aryl, heteroaryl, aralkyl, heteroarylalkyl, wherein said alkyl or aryl groups are possibly substituted with 1 to 3 R.sup.20 groups, R.sup.20 being selected from among OR.sup.22, NR.sup.23R.sup.24, NHOH, NO.sub.2, CN, CF.sub.3, a C.sub.1-C.sub.6 alkyl, a C.sub.2-C.sub.6 alkenyl, a C.sub.2-C.sub.6 alkynyl, a C.sub.6-C.sub.10 aryl, an aralkyl, ?O, C(?O)R.sup.22, CO.sub.2R.sup.22, OC(?O)R.sup.22, C(?O)NR.sup.23R.sup.24, OC(?O)NR.sup.23R.sup.24, NR.sup.21C(?S)R.sup.22 or S(O).sub.yR.sup.22; R.sup.22 is, at each occurrence, independently selected from among H, a C.sub.1-C.sub.30 alkyl, a C.sub.6-C.sub.10 aryl and an aralkyl; R.sup.23 and R.sup.24 are, at each occurrence, independently selected from among H, a C.sub.1-C.sub.30, preferably C.sub.5-C.sub.20, alkyl, and a C.sub.6-C.sub.10 aryl, or R.sup.23 and R.sup.24 form with the hydrogen atom to which they are attached a 3- to 7-membered heterocyclic group.

7. The compound according to claim 1, characterised in that R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, and R12 represent independently of one another a hydrogen atom, a halogen atom, a C.sub.1-C.sub.6 alkyl, a C.sub.2-C.sub.6 alkenyl, a C.sub.2-C.sub.6 alkynyl, a C.sub.6-C.sub.10 aryl, a C.sub.6-C.sub.20 aralkyl.

8. The compound according to claim 7, wherein A.sup.? is an anion selected from among halide, P(R.sup.4).sub.6.sup.?, B(R.sup.4).sub.4.sup.?, SCN.sup.?, (R.sup.5SO.sub.2).sub.2N.sup.?, R.sup.5OSO.sub.3, R.sub.5SO.sub.3.sup.?, carborane, carbonate, hydrogencarbonate, alcoholate, carboxylate, amidure, phosphate, SiF.sub.6.sup.?, SbF.sub.6.sup.?, I.sub.3.sup.?, nitrate, halide oxide, silicate, sulphate, sulphonate, cyanide, carbanion, or metallate, wherein: R.sup.4 is, at each occurrence, a group independently selected from among a halogen atom, a C.sub.1-C.sub.6 alkyl group, a C.sub.6-C.sub.10 aryl group, an aralkyl group; R.sup.5 is, at each occurrence, a group independently selected from among C.sub.1-C.sub.20 alkyl, C.sub.1-C.sub.20 haloalkyl, C.sub.6-C.sub.10 aryl, aralkyl.

9. The compound according to claim 1, characterised in that A.sup.? (anion) is selected from among Cl.sup.?, Br.sup.?, I.sup.?, PF.sub.6.sup.?, BF.sub.4.sup.?, (CF.sub.3SO.sub.2).sub.2N.sup.?.

10. The compound according to claim 1, characterised in that A.sup.? (anion) represents PF.sub.6.sup.? or BF.sub.4.sup.?.

11. A fluorophore solid or liquid material, comprising or consisting of a fluorophore compound, said fluorophore compound being defined according to claim 1.

12. The material according to claim 11, characterised in that the material is a transparent plastic material.

13. A use of a compound as defined according to claim 1, for the detection of the gamma, X, neutron, proton radiations.

14. The use according to claim 13, for the discrimination of the proton/gamma, proton/X, neutron/gamma, neutron/X, alpha/gamma, alpha/X radiations.

15. A use of a compound as defined according to claim 1, for the manufacture of a radio-detection, industrial or medical dosimetry instrument.

16. A method for preparing a compound of formula (I) as defined according to claim 1, said method comprising: (i) a coupling reaction of an aromatic (Het)Ar group to an imidazole group by creating a covalent bond between an sp.sup.2 carbon atom of the aromatic group and a nitrogen atom of the imidazole group, in the presence of a NaY zeolite including copper (II) and a base; and (ii) a coupling reaction of an R group comprising at least one sp.sup.3 carbon atom to an imidazole group by creating a covalent bond between the sp.sup.3 carbon atom of the R group and a nitrogen atom of the imidazole group.

Description

DESCRIPTION OF THE INVENTION

[0036] The Inventors have discovered a new family of discriminating ionic molecules (or compounds). The synthesis method allows obtaining imidazolium (salts consisting of a luminescent cation and an anion that is active in detection) in two or three steps from commercial products. This synthesis method is universal because a large number of aryls or aromatic groups can be coupled.

[0037] Moreover, the properties of these new molecules are even better with regards to the detection and discrimination of the aforementioned rays than those described in the patent WO 2010/004228.

[0038] The present invention relates to a compound or a material comprising it, said compound having one of the following ionic chemical structures:

##STR00002## [0039] R represents an alkyl or O-alkyl group, alkyl being defined as a saturated hydrocarbon radical, possibly comprising one or more unsaturation(s), in a linear or branched chain, having 1 to 30 carbon atoms, preferably 3 to 18 carbon atoms, possibly substituted; R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, and R12 represent independently of one another an atom or group of atoms; [0040] (Het)Aryl independently represents an aryl or heteroaryl group; and [0041] A represents an anion.

[0042] In particular, the present invention relates to a compound or a material comprising it, said compound having one of the following ionic chemical structures:

##STR00003## [0043] R represents an alkyl or O-alkyl group, alkyl being defined as a linear or branched chain saturated hydrocarbon radical having 1 to 30 carbon atoms, preferably 3 to 18 carbon atoms, possibly substituted; [0044] R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, and R12 represent independently of one another an atom or group of atoms; [0045] (Het)Aryl independently represents an aryl or heteroaryl group; and [0046] A.sup.? represents an anion.

[0047] According to one variant, a compound according to the invention has the following chemical structure:

##STR00004## [0048] where R, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, and R12 are as defined according to the invention.

[0049] According to one variant, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, and R12 represent, independently of one another: [0050] H, [0051] F, Cl, Br, I, [0052] a C.sub.1-C.sub.30 alkyl group, C.sub.3-C.sub.7 cycloalkyls, a C.sub.6-C.sub.10 aryl, a heteroaryl, an aralkyl, an heteroarylalkyl, wherein said alkyl or aryl groups are possibly substituted with 1 to 3 R.sup.20 groups, [0053] R.sup.20 is selected from among OR.sup.22, NR.sup.23R.sup.24, NHOH, NO.sub.2, CN, CF.sub.3, a C.sub.1-C.sub.6 alkyl, a C.sub.2-C.sub.6 alkenyl, a C.sub.2-C.sub.6 alkynyl, a C.sub.6-C.sub.10 aryl, an aralkyl, ?O, C(?O)R.sup.22, CO.sub.2R.sup.22, OC(?O)R.sup.22, C(?O)NR.sup.23R.sup.24, OC(?O)NR.sup.23R.sup.24, NR.sup.21C(?S)R.sup.22 or S(O).sub.yR.sup.22; [0054] R.sup.22 is, at each occurrence, independently selected from among H, a C.sub.1-C.sub.30-alkyl, preferably a C.sub.5-C.sub.20 alkyl, a C.sub.6-C.sub.10 aryl and an aralkyl; [0055] R.sup.23 and R.sup.24 are, at each occurrence, independently selected from among H, a C.sub.1-C.sub.30, preferably C.sub.5-C.sub.20, alkyl and a C.sub.6-C.sub.10 aryl, or R.sup.23 and R.sup.24 form, with the hydrogen atom to which they are attached, a 3- to 7-membered heterocyclic group.

[0056] According to one variant, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, and R12 represent, independently of one another, a hydrogen atom, a halogen atom, a C.sub.1-C.sub.6 alkyl group, a C.sub.2-C.sub.6 alkenyl, a C.sub.2-C.sub.6 alkynyl, a C.sub.6-C.sub.10 aryl, a C.sub.6-C.sub.20 aralkyl.

[0057] According to a variant of the present invention, the alkyl radicals represent saturated hydrocarbon radicals, in a linear or branched chain, having 1 to 30 carbon atoms, preferably 5 to 20 carbon atoms.

[0058] According to one variant, R represents an alkyl or an O-alkyl group, where alkyl is a saturated hydrocarbon radical, possibly comprising one or more unsaturation(s), in a linear or branched chain, having 5 to 12 carbon atoms.

[0059] According to a preferred variant, R represents an alkyl group or O-alkyl group, where alkyl is a saturated hydrocarbon radical, in a linear or branched chain, having 5 to 12 carbon atoms.

[0060] According to one variant, R represents an alkyl group C.sub.nH.sub.2n+1 or OC.sub.nH.sub.2n+1, where n is a number ranging from 1 to 30, and preferably from 5 to 20.

[0061] Preferably, R is selected from among the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl, decyl, dodecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, isopropyl, tert-butyl, 2-ethylhexyl, 2-methylbutyl, 2-methylpentyl, 1-methylpentyl and 3-methylheptyl radicals. Mention may in particular be made of the methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl, decyl, dodecyl, hexadecyl and octadecyl radicals when they are linear.

[0062] Mention may in particular be made of the isopropyl, tert-butyl, 2-ethylhexyl, 2-methylbutyl, 2-methylpentyl, 1-methylpentyl and 3-methylheptyl radicals, when they are branched or substituted with one or more alkyl radical(s).

[0063] Throughout the description of the invention, unless stated otherwise, the following terms should be understood as having the following meanings.

[0064] The term haloalkyl refers to an alkyl radical substituted with one or more halogen atom(s). Haloalkyl radicals include perhaloalkyl radicals and in particular perfluoroalkyl radicals of formula C.sub.nF.sub.2n+1.

[0065] The term halogen refers to a chlorine, bromine, iodine or fluorine atom.

[0066] The term cycloalkyl means a mono- or multicyclic non-aromatic ring system having 3 to 10 carbon atoms, preferably 5 to 7 carbon atoms. As example of monocyclic cycloalkyl, mention may in particular be made of cyclopentyl, cyclohexyl, cycloheptyl and the like. As example of a multicyclic cycloalkyl group, mention may in particular be made of 1-decalin, norbornyl, or adamant-(1 or 2)-yl.

[0067] The term alkenyl refers to an aliphatic hydrocarbon group which contains a carbon-carbon double bond and which may be linear or branched having 2 to 6 carbon atoms in the chain. Branched means that one or more lower alkyl group(s), such as methyl, ethyl or propyl, are bonded to a linear alkenyl chain. As example of an alkenyl group, mention may in particular be made of ethenyl, propenyl, n-butenyl, i-butenyl, 3-methylbut-2-enyl or n-pentenyl.

[0068] The term alkynyl refers to an aliphatic hydrocarbon group which contains a carbon-carbon triple bond and which may be linear or branched having 2 to 6 carbon atoms in the chain, preferably 2 to 4 carbon atoms. Branched means that one or more lower alkyl group(s), such as methyl, ethyl or propyl, are bonded to a linear alkynyl chain. As example of alkynyl groups, mention may in particular be made of ethynyl, propynyl, n-butynyl, 2-butynyl, 3-methylbutynyl, and n-pentynyl.

[0069] The term aryl refers to an aromatic monocyclic or multicyclic ring system having 5 to 20 carbon atoms. As example of aryl groups, mention may in particular be made of phenyl, possibly substituted, naphthalene, possibly substituted, fluorene, possibly substituted, methylcarbazole, possibly substituted, and anthracene, possibly substituted, pyrene, possibly substituted, tetracene, possibly substituted, bodipy, thiophene and polythiophene.

[0070] The term substituted refers to a substitution of a hydrogen atom with a halogen atom or with an alkyl, haloalkyl, cycloalkyl, alkenyl, alkynyl, aryl group, a heterocyclic group, such as a heterocycloalkyl, a heteroaryl.

[0071] The term aralkyl refers to an aryl-alkyl-group, in which the aryl and the alkyl are as described in the present document. As example of aralkyl groups, mention may be in particular be made of benzyl, 2-phenethyl and naphthylmethyl.

[0072] The term heterocyclic group refers to a substituted or unsubstituted, mono- or multicyclic carbocyclic group in which the cyclic part comprises at least one heteroatom such as O, N, S or B. The nitrogen and the sulphur may possibly be oxidised, and the nitrogen may possibly be substituted in the aromatic rings. The heterocyclic groups comprise the heteroaryl groups and the heterocycloalkyl groups.

[0073] The term heterocycloalkyl refers to a cycloalkyl group in which one or more ring carbon atom(s) is/are substituted with at least one atom selected from among O, N, or S.

[0074] As example of a heterocycloalkyl group, mention may in particular be made of pyrrolidinyl, pyrrolinyl, imidazolidinyl imidazolinyl, pirazolidinyl, pirazolinyl, pyrazalkinyl, piperidyl, piperazinyl, morpholinyl, thiomorpholinyl, tetrahydrofuranyl, dithiolyl, oxathiolyl, oxadiazolyl, oxathiazolyl, pyranyl, oxazinyl, oxathiazinyl, and oxadiazinyl.

[0075] The term heteroaryl or heteroaromatic refers to a ring system containing from 5 to 10 carbon atoms in which at least one ring carbon is replaced by at least one atom selected from among O, N, S, or B. As example of a heteroaryl group, mention may in particular be made of pyrrolyl, furanyl, thienyl, pirazolyl, imidazolyl, thiazolyl, isothiazolyl, isoxazolyl, oxazolyl, oxathiolyl, oxadiazolyl, triazolyl, oxatriazolyl, furazanyl, tetrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, indolyl, isoindolyl, indazolyl, benzofuranyl, isobenzofuranyl, purinyl, quinazolinyl, quinolyl, isoquinolyl, benzoimidazolyl, benzothiazolyl, benzothiophenyl, thianaphthenyl, benzoxazolyl, benzisoxazolyl, cinnolinyl, phthalazinyl, naphthyridinyl, and quinoxalinyl. Also covered by the definition of heteroaryl groups, the fused ring systems including in particular the ring systems in which the aromatic ring is fused with a heterocycloalkyl ring. As examples of such fused ring systems, mention may in particular be made of phthalamide, phthalic anhydride, indoline, isoindoline, and tetrahydroisoquinoline.

[0076] The term heteroarylalkyl refers to an aryl-heteroaryl-group, in which the heteroaryl and the alkyl are as described in the present document.

[0077] The term (Het)Ar or (Het)Aryl or (Het)Aromatic refers to both an aryl and an heteroaryl group.

[0078] The terms alkylene, cycloalkylene, heterocycloalkylene, arylene, heteroarylene respectively refer to divalent alkyl, cycloalkyl, heterocycloalkyl aryl and heteroaryl groups, these groups being as defined hereinabove.

[0079] The term metallate refers to an anionic complex containing a metal, in particular a transition metal complexed by several ligands, for example a chalcogen such as oxygen or a cyanide group. Preferably, the metallate anion is a cyanometallate or oxometalate group.

[0080] The term carborane refers to an anionic molecule consisting of boron, carbon and hydrogen atoms and carrying a negative charge. As example, mention may be made of CB.sub.11H.sub.12.

[0081] The term halide oxide refers to oxides of formula HalO.sub.x.sup.? where Hal represents Br, Cl or I and x is an integer from 1 to 4. As example, mention may be made of ClO.sub.4.sup.?, IO.sub.3.sup.?. The term carbanion refers to a compound comprising a carbon atom carrying a negative charge. As example, mention may be made of (CF.sub.3SO.sub.2).sub.3C.sup.?.

[0082] According to one variant, A.sup.? is an anion selected from among a halide, P(R.sup.4).sub.6.sup.?, B(R.sup.4).sub.4.sup.?, SCN.sup.?, (R.sup.5SO.sub.2).sub.2N.sup.?, R.sup.5OSO.sub.3, R.sup.5SO.sub.3.sup.?, carborane, carbonate, hydrogencarbonate, alcoholate, carboxylate, amidure, phosphate, SiF.sub.6.sup.?, SbF.sub.6.sup.?, I.sub.3.sup.?, nitrate, halide oxide, silicate, sulphate, sulphonate, cyanide, carbanion, or metallate, wherein: [0083] R.sup.4 is, at each occurrence, a group independently selected from among a halogen atom, a C.sub.1-C.sub.6 alkyl group, a C.sub.6-C.sub.10 aryl group, an aralkyl group; [0084] R.sup.5 is, at each occurrence, a group independently selected from among a C.sub.1-C.sub.20 alkyl, a C.sub.1-C.sub.20 haloalkyl, a C.sub.6-C.sub.10 aryl, an aralkyl.

[0085] According to one variant, A.sup.? (anion) is selected from among Cl.sup.?, Br.sup.?, I.sup.?, PF.sub.6.sup.?, BF.sub.4.sup.?, (CF.sub.3SO.sub.2).sub.2N.sup.?.

[0086] According to one variant, A.sup.? (anion) represents PF.sub.6.sup.? or BF.sub.4.sup.?.

[0087] According to a particular embodiment, the compound according to the present invention has the following ionic structure associating a luminescent cation with an anion that is active in the slow neutron detection:

##STR00005##

[0088] Preferably, the fluorophore compound is a compound as defined according to the invention, R comprising all of the variants and embodiments, and combinations thereof.

[0089] According to one embodiment, the compound according to the invention is solid under the conditions of use, and in particular at 20? C. and 101 325 Pa. Advantageously, the compound according to the invention is solid up to 200? C. at 101 325 Pa.

[0090] Advantageously, the invention relates to a luminescent ionic compound, preferably solid, allowing detecting both low and high energies neutrons by discriminating them from gammas.

[0091] According to a second aspect, the invention relates to a solid or liquid fluorophore material, comprising or consisting of a fluorophore compound, said fluorophore compound being defined according to the invention.

[0092] Advantageously, the material according to the invention is a transparent plastic material.

[0093] According to another aspect, the invention relates to the use of these molecules for their fluorophore properties.

[0094] Advantageously, the invention relates to the use of a compound or of a material as defined according to the invention for the detection of gamma, X, neutron, proton radiations.

[0095] Advantageously, the invention relates to the use of a compound or of a material as defined according to the invention for the discrimination of proton/gamma, proton/X, neutron/gamma, neutron/X, alpha/gamma, alpha/X radiations.

[0096] Advantageously, the invention relates to the use of a compound or of a material as defined according to the invention for the manufacture of a radio-detection, industrial or medical dosimetry instrument.

[0097] Advantageously, the invention relates to a compound and a material with a high detection efficiency and neutron detection regardless of their energy and a very good discrimination between neutrons and gammas.

[0098] Advantageously, the invention relates to a new generation compound and material having a better neutron/gamma discrimination merit factor, a high intrinsic detection efficiency, a strong luminescence in the solid state and a better thermal stability (advantageously up to 200? C.) compared to the fluorene-type material (100? C.) described by the application WO 2014/147078.

[0099] As far as the Inventors know, none of the existing competing products allows detecting both fast and slow neutrons in a satisfactory manner. Their intrinsic detection efficiency is also lower than that of the compounds according to the present invention, as well as the emitted light.

[0100] Advantageously, the invention relates to a compound and a material having a high chemical, thermal stability, without vapour pressure and allowing using it under vacuum.

[0101] Advantageously, the invention relates to a solid compound and material allowing using it in sensitive locations.

[0102] Advantageously, the invention relates to a compound the synthesis of which can be industrialised at least on the kilogram scale.

[0103] Advantageously, the invention relates to a compound in the form of crystals, and in particular single crystals, for example having a centimetric size or more.

[0104] The present invention may be implemented for the detection of neutrons both in the military and civil fields, some applications being common to both. A list of possible applications is given hereafter: [0105] 1) radiation monitoring on workplaces and in the environment [0106] 2) fissile material monitoring in nuclear wastes [0107] 3) detection of fissile materials in suspicious packages [0108] 4) nuclear diagraphy [0109] 5) R&D for nuclear energy [0110] 6) cosmic radiation study, cosmic ray monitoring in aircrafts [0111] 7) neutron radiography [0112] 8) physics fundamental research

[0113] Advantageously, the invention relates to a compound and a material for the manufacture of a scintillator containing only organic molecules synthesised from easily accessible raw materials.

[0114] Advantageously, the invention relates to a compound and a material offering the possibility of miniaturising the devices and making them portable.

[0115] Furthermore, advantageously, the invention relates to a compound and a material allowing for a reduction in the costs to a few tens of euros per gram compared to about 15 k the gram for .sup.3He.

[0116] The needs for low-energy neutrons (slow neutrons) are covered essentially by .sup.3He gaseous detectors, the marketing of which will be no longer possible in few years given the rarefaction of .sup.3He on Earth. These devices detect only low-energy neutrons.

[0117] According to another aspect, the present invention also relates to a synthesis method allowing preparing compounds according to the invention.

[0118] In particular, the invention relates to a method for preparing a compound comprising an imidazolium group bonded directly to an aromatic group by a covalent bond between a nitrogen atom of the imidazolium group and a carbon atom of said aromatic group, said method comprising a reaction of coupling an aromatic group to an imidazole group by creating a covalent bond between an sp.sup.2 carbon atom of the aromatic group and a nitrogen atom of the imidazole group, in the presence of a NaY zeolite including copper (II) and a base, preferably by Ullmann-type coupling.

[0119] According to a particular embodiment, the invention relates to the preparation of a compound of formula (I) according to the invention, said method comprising: [0120] (i) a reaction of coupling a (Het)Ar aromatic group to an imidazole group by creating a covalent bond between an sp.sup.2 carbon atom of the aromatic group and a nitrogen atom of the imidazole group, in the presence of a NaY zeolite including copper (II) and a base, preferably by Ullmann-type coupling; and [0121] (ii) a reaction of coupling an R group comprising at least one sp.sup.3 carbon atom with an imidazole group by creating a covalent bond between the carbon atom sp.sup.3 of the R group and a nitrogen atom of the imidazole group, preferably by nucleophilic substitution, preferably using a halogenated reactive R group.

[0122] According to one variant, step (i) corresponds to the following reaction:

##STR00006##

where X is a halogen atom, preferably the reaction being carried out in the presence of microwave radiations.

[0123] Typically, according to the invention, the RX group represents the structure:

##STR00007##

[0124] The catalyst is simple to prepare: the NaY zeolite is placed in the presence of copper sulphate dissolved in water and stirred for 24 hours. The zeolite impregnated with copper (II) is recovered by filtration, dried in the oven (100? C.) and then calcined at 550? C. for 4 hours. Reference may in particular be made to the publication by M. L. Kantam, B. P. C. Rao, B. M. Choudrary, R. S. Reddy, Synlett, 2006, 14, 2195-2198. doi: 10.1055/s-2006-949615.

[0125] During the Ullmann coupling (J. Hassan, M. Sevignon, C. Gozzi, E. Schulz, M. Lemaire, Aryl-Aryl Bond Formation One Century after the Discovery of the Ullmann Reaction, Chemical Reviews, vol. 102, 2002, p. 1359-1470), the reagents are heated, for example, in a tube sealed for 72 hours at 180? C. using a sand bath. To recover the reaction crude, all it needs is to carry it on in an organic solvent such as dichloromethane and to filter in order to remove the zeolite and the base (potassium carbonate). The imidazole derivative thus obtained is purified, for example, by column chromatography.

[0126] Although it does not use a solvent or an inert atmosphere, it is necessary to heat the reaction mixture necessary for coupling of the imidazole and the aryl, for example by heating to a temperature of 180? C. for 72 hours.

[0127] Advantageously, the reaction is carried out in the presence of microwave radiations. By this method, the Inventors have been able to reduce the reaction time quite substantially. It is possible to reduce a reaction time from 72 hours (in a sealed tube heated with a sand bath) to less than 3 hours and that being so for identical yields.

[0128] Microwaves are electromagnetic waves that have a wavelength comprised between 30 cm (1 GHz) and 1 mm (300 GHz).

[0129] Preferably, the base is selected from among a potassium or cesium carbonate, a potassium phosphate, a cesium phosphate, LiOH, NaOH, or KOH.

[0130] Advantageously, the method according to the present invention does not require any solvent. According to the prior art, the synthesis methods require the use of a solvent (dimethylformamide, dimethyl sulfoxide, toluene, etc.), which is avoided in the present invention.

[0131] The present invention allows avoiding the use of amine ligands (carbene, phenanthroline, I-proline, etc.).

[0132] This method allows avoiding the use of solvents, of an inert atmosphere and of expensive ligands, and allows preparing the compounds of the invention in only two or three steps. Moreover, the method according to the invention allows using commercially-available molecules.

[0133] Quite advantageously, the use of microwave radiations during the Ullmann-type coupling allows significantly reducing the reaction time. Thus, the reaction time can switch from 72 to less than 3 hours.

[0134] The first synthesis step consists in carrying out the Ullmann-type coupling, between an imidazole, i.e. a molecule comprising an imidazole group, and a molecule bearing a halogenated aromatic group, i.e. bearing a halogen atom on a carbon atom, a halogen atom which will be replaced by imidazole.

[0135] The second step consists in making the imidazole thus obtained react with an RX molecule to create a covalent bond between the imidazole and an sp.sup.3 carbon atom of this molecule.

[0136] According to one variant, this second step consists in carrying out an N-alkylation, i.e. making the imidazole react with an alkyl radical to create an N-alkyl bond between the alkyl radical and the nitrogen atom of the imidazole (nitrogen atom bearing no aromatic group grafted by Ullmann coupling).

[0137] A possible third step consists in exchanging the halide anion in order to obtain a fluorophore compound. This third step may be carried out in a biphasic medium.

[0138] It is possible to use the potassium, lithium, or sodium salt of the desired anion.

[0139] Possibly, said method may also comprise the step consisting in isolating the obtained product.

[0140] The method of the invention is particularly interesting as it can be extrapolated on an industrial scale because of the small number of synthesis steps, of the used reagents, which are commercial, as well as the equipment for the reactions, which can be used on a larger scale for industrial reactions.

[0141] In particular, the invention covers devices comprising the compounds of the invention, suitable for use in nuclear power plants, hospitals, airports, or similar locations.

[0142] The compounds of the invention having no measurable vapour tension can be used under vacuum.

[0143] The specific applications of the compounds of the invention depend on the considered molecule and vary according to the nature of the anion, of the cation (initial imidazole) and of the aromatic group, which must in particular serve as a fluorophore.

[0144] One could consider that the use of compounds of the invention allows lowering the detection threshold and the sensitivity of existing installations in the fields such as nuclear safety (radioprotection, proliferation of nuclear wastes or weapons, nuclear reactor) and fundamental research.

[0145] To characterise this product and verify its purity, conventional analyses methods such as nuclear magnetic resonance (NMR), infrared (IR), ultraviolet/visible (UV/visible) spectroscopy and analyses have been carried out.

[0146] These techniques have been used to characterise the synthesised compounds.

[0147] Advantageously, the compounds of the invention may be used pure, i.e. in the form of a material consisting essentially of at least one compound of the invention. Advantageously, a high concentration allows increasing as much the radiation detection efficiency. The previously-described compounds (NE213 or BC501) do not enable the use of high concentrations because their radiation detection power decreases starting from a given concentration. Thus, in this respect, the invention is a major improvement. The invention also covers the use of the compounds of the invention in a diluted form, as a filler in polymer matrices, as components of composite materials. The concentration of the compounds of the invention may be from 1 to 80% by weight in a polymer or in a solvent.

Example

Example 1Procedure for the Synthesis of NPOP-imidazole (2-(4-(1H-imidazol-1-yl)phenyl)-5-phenyloxazole) by Ullmann Type Coupling

[0148] 2-(4-bromophenyl)-5-phenyloxazole (POPBr) (71.5 g, 238 mmol), imidazole (24.32 g, 357.3 mmol), potassium carbonate (65.84 g, 476.4 mmol) and NaY zeolite doped with copper at 8% are ground together using a mortar. The obtained powder is introduced into a 800 ml Teflon microwave reactor equipped with a magnetic stirring blade. The medium is heated up to 210? C. for 3 h. After cooling, the obtained solid is ground into fine powder and then extracted with dichloromethane. Filtration on Celite allows obtaining the product, which is then purified by conventional laboratory techniques. The NPOP-imidazole is obtained in the form of a white powder (64.1 g, 223.1 mmol, 93%).

##STR00008##

[0149] .sup.1H NMR (500 MHz, Chloroform-d): ?=8.21 (AA, .sup.3J.sub.H9-H10=8.7 Hz, 2H, H.sub.9), 7.94 (s, 1H, H.sub.12), 7.72 (d, .sup.3J.sub.H3-H2=8.0 Hz, 2H, H.sub.3), 7.50 (BB, .sup.3J.sub.H10-H9=8.7 Hz, 2H, H.sub.10), 7.46 (s, 1H, H6), 7.45 (t, .sup.3J.sub.H2-(H3+1)=7.8 Hz, 2H, H.sub.2), 7.34 (tt, .sup.3J.sub.H1-H2=7.4 Hz, .sup.4J.sub.H1-H2=1.3 Hz, 1H, H.sub.1), 7.35 (s large, 1H, H.sub.13), 7.24 (s large, 1H, H.sub.14).

[0150] .sup.13C NMR (125 MHz, Chloroform-d): ?=160.12 (C.sub.7), 151.91 (C.sub.5), 138.72 (C.sub.8), 135.60 (large, C.sub.lm), 131.09 (C.sub.lm), 129.19 (C.sub.10), 128.92 (C.sub.1), 128.06 (C.sub.9), 127.92 (C.sub.4), 126.69 (C.sub.11), 124.45 (C.sub.3), 123.82 (C.sub.6), 121.57 (C.sub.2), 118.07 (br, C.sub.lm).

[0151] IR: ?.sub.max/cm.sup.?1=3107 (wide, ?.sub.CH aromatic), 1614, 1504, 1303, 1054, 951, 833, 767, 725, 691, 651, 492.

[0152] UV-Vis (MeCN): ?.sub.max=316 nm, ?.sub.max=38.000 L.Math.mol.sup.?1.Math.cm.sup.?1.

[0153] Element analysis for (C.sub.18H.sub.13N.sub.3O.sub.1). Calculated: C, 75.25; H, 4.56; N, 14.63. Found: C, 75.30; H, 4.58; N, 14.82.

Example 2Procedure for the Synthesis of NPOPN-hexylimidazolium bromide (3-hexyl-1-(4-(5-phenyloxazol-2-yl)phenyl)-1H-imidazol-3-ium bromide

[0154] NPOP-imidazole (40 g, 139 mmol) is suspended in acetonitrile (40 ml) and n-bromohexane (60 ml, 418 mmol) in an autoclave. The medium is stirred at 120? C. for 48 h; then, after cooling, the reaction medium is poured onto diethyl ether (500 ml). The product is recovered by filtration, and is washed again with 3 portions of 100 ml of diethyl ether. To achieve an optimum purity, the product is purified according to conventional laboratory techniques. The product is obtained in the form of a white powder (60.152 g, 133 mmol, 95%).

##STR00009##

[0155] .sup.1H NMR (500 MHz, Chloroform-d): ?=11.04 (t, .sup.3J.sub.H12-(H13+14)=1.8 Hz, 1H, H.sub.12), 8.16 (AA, .sup.3J.sub.H9-H10=8.8 Hz, 2H, H.sub.9), 8.07 (t, .sup.3J.sub.H13-(H12+14)=1.8 Hz, 1H, H.sub.13), 8.00 (BB, .sup.3J.sub.H10-H9=8.8 Hz, 2H, H.sub.10), 7.73 (t, .sup.3J.sub.H14-(H12+13)=1.8 Hz, 1H, H.sub.14), 7.60 (d, .sup.3J.sub.H3-H2=8.3 Hz, 2H, H.sub.3), 7.37 (t, .sup.3J.sub.H2-(H3+1)=7.8 Hz, 2H, H.sub.2), 7.36 (s, 1H, H.sub.6), 7.29 (tt, .sup.3J.sub.H1-H2=7.4 Hz, .sup.4J.sub.H1-H2=1.2 Hz, 1H, H.sub.1), 4.53 (t, .sup.3J.sub.H15-H16=7.3 Hz, 2H, H.sub.15), 1.97 (m, 2H, H.sub.16), 1.37 (m, 2H, H.sub.17), 1.37 (m, 4H, H.sub.18+19), 0.81 (t, 3H, .sup.3J.sub.H20-H19=7.1 Hz H.sub.20).

[0156] .sup.13C NMR (125 MHz, Chloroform-d): ?=159.11 (C.sub.7), 152.22 (C.sub.5), 135.95 (C.sub.12), 135.38 (C.sub.8), 129.12 (C.sub.2), 128.98 (C.sub.1), 128.94 (C.sub.4), 128.20 (C.sub.9), 127.47 (C.sub.11), 124.39 (C.sub.3), 123.86 (C.sub.6), 123.43 (C.sub.14), 122.26 (C.sub.10), 120.90 (C.sub.13).

[0157] IR: ?.sub.max/cm.sup.?1=3523 (wide, ?.sub.OH); 3079 (?.sub.CH aromatic); 2960, 2929, 2856 (?.sub.CH aliphatic); 1551, 1498, 1206, 1135, 1059, 952, 842, 769, 737, 694, 623, 532, 493.

[0158] UV-Vis (MeCN): ?.sub.max=321 nm, ?.sub.max=33.200 L.Math.mol.sup.?1.Math.cm.sup.?1.

[0159] Element analysis (C.sub.24H.sub.26BrN.sub.3O.sub.1). Calculated: C, 63.72; H, 5.79; N, 9.29. Found: C, 62.76; H, 5.71; N, 9.29. The element analysis corresponds to the product containing 0.5 H.sub.2O molecule per molecule, which is consistent with the presence of ?.sub.OH vibrations in the infrared spectrum (Calculated: C, 62.48; H, 5.90; N, 9.11).

Example 3Procedure for the Synthesis of NPOPN-hexylimidazolium tetrafluoroborate (3-hexyl-1-(4-(5-phenyloxazol-2-yl)phenyl)-1H-imidazol-3-ium tetrafluoro borate

[0160] NPOPN-hexylimidazolium bromide (23.7 g, 52.4 mmol) is dissolved at 50? C. in 350 ml of ethanol. Sodium tetrafluoroborate (8.63 g, 78.6 mmol) is dissolved in 50 ml of water and this solution is added to the imidazolium salt solution. The medium becomes slightly turbid and is stirred at room temperature for 1 h. Afterwards, water (1.5 L) is added in order to make the product precipitate, which is then recovered by filtration. The obtained white powder is dissolved in 500 ml of a 10% dichloromethane/methanol solution, then the obtained solution is dried over magnesium sulphate. The liquid is filtered, evaporated and then the obtained solid is purified according to conventional laboratory techniques in order to remove the remaining imidazolium bromide. NPOPN-hexylimidazolium tetrafluoroborate is obtained in the form of a microcrystalline white powder (22.737 g, 49.5 mmol, 94%).

##STR00010##

[0161] .sup.1H NMR (500 MHz, DMSO-d.sub.6): ?=9.91 (t, .sup.3J.sub.H12-(H13+14)=1.7 Hz, 1H, H.sub.12), 8.42 (t, .sup.3J.sub.H13-(H12+14)=1.8 Hz, 1H, H.sub.13), 8.37 (AA, .sup.3J.sub.H9-H10=8.8 Hz, 2H, H.sub.9), 8.07 (t, .sup.3J.sub.H14-(H12+13)=1.7 Hz, 1H, H.sub.14), 7.98 (BB, .sup.3J.sub.H10-H9=8.8 Hz, 2H, H.sub.10), 7.92 (s, 1H, H.sub.6), 7.90 (d, .sup.3J.sub.H3-H2=8.0 Hz, 2H, H.sub.3), 7.52 (t, .sup.3J.sub.H2-(H3+1)=7.7 Hz, 2H, H.sub.2), 7.42 (tt, .sup.3J.sub.H1-H2=7.3 Hz, .sup.4J.sub.H1-H2=1.3 Hz, 1H, H.sub.1), 4.46 (t, .sup.3J.sub.H15-H16=7.3 Hz, 2H, H.sub.15), 1.91 (m, 2H, H.sub.16), 1.32 (m, 6H, H.sub.17-19), 0.88 (t, 3H, .sup.3J.sub.H20-H19=7.1 Hz H.sub.20).

[0162] .sup.13C NMR (125 MHz, DMSO-d.sub.6): ?=158.91 (C.sub.7), 151.4 (C.sub.5), 135.96 (C.sub.8), 135.47 (C.sub.12), 129.10 (C.sub.2), 128.87 (C.sub.1), 127.60 (C.sub.4), 127.55 (C.sub.9), 127.14 (C.sub.11), 124.51 (C.sub.6), 124.21 (C.sub.3), 123.44 (C.sub.14), 122.39 (C.sub.10), 129.92 (C.sub.13).

[0163] IR: ?.sub.max/cm.sup.?1=3148, 3101 (?.sub.CH aromatic); 2957, 2928, 2859 (?.sub.CH aliphatic); 1556, 1499, 1212, 1135; 1068 (wide, very intense, ?.sub.BF); 951, 840, 773, 737, 695, 625, 521, 494.

[0164] UV-Vis (MeCN): ?.sub.max=321 nm, ?.sub.max=33.100 L.Math.mol.sup.?1 cm.sup.?1.

[0165] Element analysis (C.sub.24H.sub.26BF.sub.4N.sub.3O.sub.1). Calculated: C, 63.76; H, 5.71; N, 9.15. Found: C, 62.78; H, 5.76; N, 9.21.

[0166] This compound is stable at 200? C.

[0167] This compound is highly luminescent (70%)

[0168] Measurements have been performed by irradiating the new materials with a fast neutron and gamma emitter AmBe source. The sample is placed on a photomultiplier PHOTONIS XP4512B which produces an electrical signal processed by digital electronics (FASTER developed in the Caen Corpuscular Laboratory (LPC)). Two integration gates allow matching the total and slow charges of the signal: a 300 ns gate covers the entire signal and a gate delayed by 50 ns and stopping at the same time as the total gate covers the slow component of the signal.

[0169] FIG. 1 shows, for the compound of Example 3, the correlations between the total charge Q.sub.tot and the ratio Q.sub.lent/Q.sub.tot obtained by irradiation of the AmBe source:

[0170] FIG. 1a): an excellent discrimination between neutrons and gammas is obtained.

[0171] FIG. 1b): a polyethylene layer with a thickness of 10 cm placed in front of the detector allows slowing down the neutrons coming from the source. These, thermalised, will interact with the .sup.10B and produce alphas. Not all neutrons are thermalised and a small fast neutron component subsists.

[0172] The peak observed in the gamma component (Q.sub.tot?60000 cx) of FIG. 1a) corresponds to the photopic resulting from the alpha disintegration of the .sup.241Am to an excited state of the .sup.237Np, the return of which to the fundamental releases a gamma ray of 59.54 keV. This shows the very low energy threshold of this compound which allows detecting fast neutrons in an energy area (E<1 MeV) generally difficult to access by existing detectors.

[0173] A major feature of the neutron detectors is their discrimination between neutrons and gammas, determined by the figure of merit (FOM, Figure of merit). The compound shown in FIG. 1 has a FOM?2, a very satisfactory value for separating the neutrons from the gammas.

Example 4Comparison of the Performances of a Material According to the Invention with a Fluorene-Based Material

[0174] The performances of the material obtained in Example 3 hereinabove have been compared with those of a 1(9H-fluoren-2-yl)-3-hexyl-1H-imidazol-3-ium tetrafluoro borate material, so-called fluorene-type compound of formula:

##STR00011##

[0175] The compound of Example 3 differs from the fluorene-type compound by the substitution of the fluorene group with a 4-(5-phenyloxazol-2-yl)phenyl group, in particular by the substitution of the condensed cyclopentane of the fluorene-type compound with an oxazole group.

a) Irradiation with a UV (Ultraviolet) Radiation

[0176] The two samples are irradiated simultaneously by a UV light. It is observed that the material according to the invention is much more luminescent than the fluorene-type compound.

b) Irradiation with an AmBe Radiation

[0177] Measurements have been carried out by irradiating the two materials with a fast neutron and gamma emitter AmBe source. The sample is placed on a photomultiplier PHOTONIS XP4512B which produces an electrical signal processed by digital electronics (FASTER developed in the Caen Corpuscular Laboratory (LPC)). Two integration gates allow matching the total and slow charges of the signal: a 300 ns gate covers the entire signal and a gate delayed by 50 ns and stopping at the same time as the total gate covers the slow component of the signal.

[0178] FIG. 2 shows, for the fluorene-type compound, the correlations between the total charge Qtot and the ratio Qlent/Qtot obtained by irradiation of the AmBe source.

[0179] FIG. 3 shows for the compound of Example 3 the correlations between the total charge Qtot and the ratio Qlent/Qtot obtained by irradiation of the AmBe source.

[0180] FIGS. 2b) and 3b) have been obtained by placing a polyethylene layer having a thickness of 10 cm in front of the detector in order to slow down the neutrons coming from the source. These, thermalised, will interact with the 10B and produce alpha. Not all neutrons are thermalised and a small fast neutron component subsists.

[0181] By comparing FIGS. 2a) and 3a), it is observed that the discriminating power of the compound of Example 3 is substantially improved, compared to the fluorene-type material. In addition, the gain in luminescence yield associated with the compound of the invention is multiplied by 2, compared to the fluorene compound.

[0182] In addition, in the context of the compound of the invention, the .sup.237Np photopic resulting from the ? decrease of .sup.241Am is clearly visible, which demonstrates the possibility of obtaining lower detection thresholds and therefore also addressing the fast neutrons of lower energy.

[0183] By comparing FIGS. 2b) and 3b), it is observed in the case of the material of the invention that the ? component produced by the .sup.10B(n, ?).sup.7Li* reaction is substantially better separated from the background noise and from the ? component, with respect to the fluorene compound.

Example 5Luminescence Quantum Yield of a Material According to the Invention

[0184] The quantum yield of the material obtained in Example 1 hereinabove has been measured according to the following protocol:

[0185] The luminescence quantum yield measurements have been carried out from the material in the solid state, in the form of a polycrystalline powder. The measurements have been carried out using an integrating sphere system coupled to a multichannel photonic analyser (Hamamatsu Quantaurus).

[0186] The time-resolved measurements have been performed using the time-correlated single photon counting (TCSPC) electronics PicoHarp300 or multi-channel scaling (MCS) electronics NanoHarp 250 of the PicoQuant FluoTime 300 (PicoQuant GmbH, Germany), equipped with a laser pulse driver PDL 820. A pulsed laser diode LDH-P-C-375 (?=375 nm, FWHM pulse <70 ps, repetition rate 200 kHz-40 MHz) has been used to excite the sample and mounted directly on the sample chamber at 90?. The photons have been collected by a photomultiplier detector (PMT) with single photon counting PMA-C-192.

[0187] The data have been acquired using the commercial software EasyTau (PicoQuant GmbH, Germany), whereas the analysis of the data has been performed using the commercial software FluoFit (PicoQuant GmbH, Germany).

[0188] The luminescence quantum yield measured from the compound obtained in Example 1 is equal to 67?2.5%, with a lifetime of 2 ns (excitation=290 nm, emission=407, 10 MHz).

[0189] The luminescence quantum yield of the compound of Example 3 according to the invention is about two times higher than the luminescence quantum yield associated with the fluorene-type compound. Thus, the fast neutron detection thresholds are significantly lowered in the context of the compound of Example 3, compared to the fluorene-type compound. Similarly, the alpha component resulting from the detection of slow neutrons can be distinguished more clearly from the background noise in the context of the compound of Example 3, compared to the fluorene-type compound.