Nanoparticle of a Spin Transition Compound

Abstract

The invention relates to a material composed of nanoparticles essentially comprising a spin transition compound. The compound corresponds to the formula [(Fe 1-y M y L 3 ) w L 3 ][X 2/x(1-z/x′) Y 2z/x′ ] w in which L represents a 1,2,4-triazole ligand carrying an R substituent on the nitrogen in the 4 position; X is an anion having the valency x, 1≦x≦2; Y is an anion other than X having the valency x′, 1≦x′≦2; R is an alkyl group or an R 1 R 2 N— group in which R 1 and R 2 represent, each independently of the other, H or an alkyl radical; M is a metal having a 3d 4 , 3d 5 , 3d 6 or 3d 7 configuration, other than Fe; 0≦y≦1; 0≦z≦2; 3≦w≦1500. Applications: thermochromic pigment, data storage, optical limiters, contrast agent.

1 . A material composed of nanometric particles comprising a compound corresponding to the formula:
   [(Fe 1-y M y L 3 ) w L 3 ][X 2/x(1-z/x′) Y 2z/x′ ] w      
     in which:
 L represents a 1,2,4-triazole ligand carrying an R substituent on the nitrogen in the 4 position; 
 X is an anion having the valency x, 1≦x≦2; 
 Y is an anion other than X having the valency x′, 1≦x′≦2; 
 R is an alkyl group or an R 1 R 2 N— group in which R 1  and R 2  represent, each independently of the other, H or an alkyl radical; 
 M is a metal having a 3d 4 , 3d 5 , 3d 6  or 3d 7  configuration, other than Fe; 
 0≦y≦1; 
 0≦z≦2; 
 3≦w≦1500. 
 
   
   
       2 . The material as claimed in  claim 1 , wherein the particles have a mean diameter between 1 nm and 500 nm. 
   
   
       3 . The material as claimed in  claim 1 , wherein R is an alkyl group having from 1 to 8 carbon atoms, or R is an R 1 R 2 N— group in which R 1  and R 2  represent, independently of one another, H or an alkyl group having from 1 to 8 carbon atoms. 
   
   
       4 . (canceled) 
   
   
       5 . The material as claimed in  claim 1 , wherein each of the anions X and Y represents, independently of the other, a monovalent anion selected from the group consisting of BF 4   − , ClO 4   − , Br − , Cl −  and NO 3   −  or a divalent anion selected from the group consisting of SO 4   2−  and CO 3   2− . 
   
   
       6 . The material as claimed in  claim 1 , corresponding to the formula Fe(L) 3 (X 2/x ) 2  or to the formula Fe 1-y M y (L) 3 (X 2/x ) 2 . 
   
   
       7 . (canceled) 
   
   
       8 . The material as claimed in  claim 1 , wherein M represents Zn, Mn, Ni or Co. 
   
   
       9 . The material as claimed in  claim 1 , wherein the complex nanoparticles are coated with a silica film. 
   
   
       10 . A process for the preparation of a material as claimed in  claim 1 , wherein a solution of Fe(II) salt and optionally of a precursor of the metal M in a solvent or a mixture of solvents is mixed with a solution of ligand L in a solvent or a mixture of solvents. 
   
   
       11 . The process as claimed in  claim 10 , comprises comprising the following stages:
 a) preparation of an emulsion of the water-in-oil type by addition, with vigorous stirring, of a composition of oil possessing surfactant properties type to an aqueous solution of at least one iron salt comprising ascorbic acid;   b) preparation of an emulsion of the water-in-oil type by addition, with vigorous stirring, of a composition of oil possessing surfactant properties type to an aqueous solution of a ligand;   c) mixing the two emulsions, followed by further vigorous stirring, for a time of 1 to 10 min;   d) precipitation of the nanoparticles by addition of a solvent which does not modify the structure of the nanoparticles but which denatures the emulsion;   e) extraction of the precipitate by several “washing with said solvent/centrifuging” cycles, followed by evaporation of said solvent.   
   
   
       12 . The process as claimed in  claim 11 , wherein the composition of the oil possessing surfactant properties type is a composition obtained by addition of a surfactant to an oil or a single product having both surfactant properties and oil properties. 
   
   
       13 . The process as claimed in  claim 10 , comprising the following stages:
 a. preparation of a microemulsion of the water-in-oil type by addition of an aqueous solution of at least one iron salt to a solution of a surfactant in an oil (n-heptane, for example) and subjecting to ultrasound until a clear solution is obtained;   b. preparation of a microemulsion of the water-in-oil type by addition of an aqueous solution of ligand to a solution of a surfactant in an oil and subjecting to ultrasound until a clear solution is obtained;   c. mixing the two microemulsions and treating the mixture with ultrasound until a clear solution is obtained;   d. precipitation of the nanoparticles by addition of a solvent which does not modify the structure of the nanoparticles but which denatures the emulsion.   
   
   
       14 . The process as claimed in  claim 11  for the preparation of a material composed of nanoparticles of a compound
   [(Fe 1-y M y L 3 ) w L 3 ][X 2/x(1-z/x′) Y 2z/x′ ] w      
     in which y≠0 and z=0, wherein an aqueous solution of M salt is prepared and added to the aqueous solution of Fe salt, before bringing into contact with the “surfactant+oil” mixture. 
   
   
       15 . The process as claimed in  claim 11  for the preparation of a material composed of nanoparticles of a compound
   [(Fe 1-y M y L 3 ) w L 3 ][X 2/x(1-z/x′) Y 2z/x′ ] w      
     in which z≠0 and y=0, wherein an aqueous solution comprising an Fe salt of one of the anions and an Fe salt of the other anion is prepared, before bringing into contact with the “surfactant+oil” mixture. 
   
   
       16 . The process as claimed in  claim 11  for the preparation of a material composed of nanoparticles of a compound
   [(Fe 1-y M y L 3 ) w L 3 ][X 2/x(1-z/x′) Y 2z/x′ ] w      
     in which y≠0 and z≠0, wherein a solution comprising at least one iron salt of one of the anions and at least one M salt of the other anion is prepared. 
   
   
       17 . The process as claimed in  claim 11  for the preparation of a material composed of nanoparticles of a compound
   [(Fe 1-y M y L 3 ) w L 3 ][X 2/x(1-z/x′) Y 2z/x′ ] w      
     in which the nanoparticles are coated with silica, wherein a silyl derivative is added to the reaction medium before stage d). 
   
   
       18 . The process as claimed in  claim 17 , wherein the silyl derivative is tetraethoxysilane, (n-octadecyl)triethoxysilane or (n-octyl)triethoxysilane. 
   
   
       19 . The use of a material as claimed in  claim 1  as thermochromic pigment, as support for data storage, as optical limiters, or as optical gate. 
   
   
       20 . (canceled) 
   
   
       21 . (canceled) 
   
   
       22 . (canceled) 
   
   
       23 . A contrast agent for the detection of cancer cells, comprising a material as claimed in  claim 1 .