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 2 ? ? z 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 R1R2N— group in which R1 and R2 represent, each independently of the other, H or an alkyl radical; M is a metal having a 3d4, 3d5, 3d6 or 3d7 configuration, other than Fe; 0?y?1; 0?z?2; 3?w?1500. Applications: thermochromic pigment, data storage, optical limiters, contrast agent.

Abstract: A material is composed of at least one spin transition compound that corresponds to the formula Fe1-mMm(R-Trz)3XbYc (I) in which M is a metal having a 3d4, 3d5, 3d6 or 3d7 configuration, other than Fe; 0?m?1; R-Trz represents a 1,2,4-triazole ligand carrying an R substituent on the nitrogen in the 4 position; R is an alkyl group or an R1R2N— group in which R1 and R2 represent, each independently of the other, H or an alkyl radical; X represents at least one noncoloring monovalent or divalent anion; Y represents at least one anion which has a coloring group; and b and c are chosen so that the electrical neutrality of the compound (I) is adhered to. A process for the preparation of this material and to its use as thermochromic pigment, as support for data storage or as optical limiter.

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 2 ? ? z 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 R1R2N— group in which R1 and R2 represent, each independently of the other, H or an alkyl radical; M is a metal having a 3d4, 3d5, 3d6 or 3d7 configuration, other than Fe; 0?y?1; 0?z?2; 3?w?1500. Applications: thermochromic pigment, data storage, optical limiters, contrast agent.

Abstract: The invention relates to a material composed of at least one spin transition compound. The compound corresponds to the formula Fe1-mMm(R-Trz)3XbYc (I) in which M is a metal having a 3d4, 3d5, 3d6 or 3d7 configuration, other than Fe; 0?m?1; R-Trz represents a 1,2,4-triazole ligand carrying an R substituent on the nitrogen in the 4 position; R is an alkyl group or an R1R2N-group in which R1 and R2 represent, each independently of the other, H or an alkyl radical; X represents at least one noncoloring monovalent or divalent anion; Y represents at least one anion which has a coloring group; and b and c are chosen so that the electrical neutrality of the compound (I) is adhered to. The invention also relates to the process for the preparation of the material and to its use as thermo-chromic pigment, as support for data storage or as optical limiter.

Abstract: The invention relates to a material composed of nanoparticles essentially comprising a spin transition compound. The compound corresponds to the formula [(Fe1-yMyL3)wL3][X2/x(1-z/x?)Y2z/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 R1R2N— group in which R1 and R2 represent, each independently of the other, H or an alkyl radical; M is a metal having a 3d4, 3d5, 3d6 or 3d7 configuration, other than Fe; 0?y?1; 0?z?2; 3?w?1500. Applications: thermochromic pigment, data storage, optical limiters, contrast agent.