Langmuir-Blodgett Films of Spin Transition Iron(II) Metalloorganic Polymers. 1. Iron(II) Complexes of Octadecyl-1,2,4-triazole

Armand, F.; Badoux, C.; Bonville, P.; Ruaudel‐Teixier, A.; Kahn, O.

doi:10.1021/la00009a032

Cited by 65 publications

(48 citation statements)

References 2 publications

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“…[6] Among the spin-crossover Fe II /triazole materials, we have focused on the solid precursor of formula [Fe II (C 18 trz) 3 ]-(ptol) 2 ·2 H 2 O (1, ptol = para-tolylsulfonate; C 18 trz = 4-octadecyl-1,2,4-triazole). This SC material presents two interesting features: it contains ptol anions inducing a spin-crossover around room temperature [7] and it contains triazole ligands functionalized by long alkyl chains which are typically introduced to obtain gelator or mesogenic molecules. [8] Compound 1 can be easily obtained by reaction of aqueous solutions of [Fe(ptol) 2 ]·6 H 2 O with ethanolic solutions of C 18 trz (Scheme 1).…”

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confidence: 99%

Thermoreversible Gels as Magneto‐Optical Switches

et al. 2004

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Polyfunctional gels: Thermoreversible switchable gels with tunable magnetic, optical, and rheological properties are obtained from a modified spin‐crossover polymeric precursor and alkane solvents (see picture). The iron triazole polymer which acts as the gelator, undergoes a spin crossover that is accompanied by a change in the color of the gel. The transfer of spin‐crossover properties from solid materials into gels offers a route to new applications.

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confidence: 99%

Thermoreversible Gels as Magneto‐Optical Switches

et al. 2004

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“…[4] However, the few attempts to build LB multilayers from iron(II) complexes with ligands based on a phenanthroline or a triazole have illustrated the high chemical instability of such compounds at the gas± water interface. [5,6] One possible way to solve this problem is to modify the sub-phase on which the Langmuir film is obtained. [7] Another possible strategy relies on subtle changes in the chemical structure of the iron complex in order to obtain a perfectly stable monolayer at the gas±water interface.…”

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confidence: 99%

“…[5] The majority of the film preparation procedures have utilized the routine thermal polycondensation. On the other hand, fewer reports describe the formation of sol-gel films by photopolymerization [6] or via electrochemical approaches, [7] despite the popularity of these film formation techniques in many other domains of materials science. Examples of the use of electrochemical methods, the topic of this paper, include electrophoretic deposition of colloidal metal hydroxide particles, [7d,7f,7i] the electrodeposition of alkoxysilane modified redox dyes [7h] and the electrooxidation of metals followed by precipitation of the resulting hydroxides.…”

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First Magnetic Observation of a Spin Crossover in a Langmuir-Blodgett Film

et al. 1999

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For particular transition metal complexes, spin crossover processes [1] occurring between a low-spin (LS) and a highspin (HS) state may be triggered by a change in temperature or pressure or by light irradiation. This striking phenomenon may appear either very gradually, as expected from a thermal equilibrium between the two spin states, or with some abruptness when intersite interactions are strong enough.[2] When the cooperativity is important, thermal hysteresis may appear, leading to new bistable materials.[3]These characteristics of the spin crossover depend greatly on the molecular surroundings and on the structure of the material. Therefore, the organization of the complexes is one of the most important factors in modifying and controlling the spin conversion. Thus, the Langmuir±Blodgett (LB) technique may lead to interesting materials because of its ability to pack and orient molecules in a well-defined fashion along a surface. [4] However, the few attempts to build LB multilayers from iron(II) complexes with ligands based on a phenanthroline or a triazole have illustrated the high chemical instability of such compounds at the gas± water interface. [5,6] One possible way to solve this problem is to modify the sub-phase on which the Langmuir film is obtained. [7] Another possible strategy relies on subtle changes in the chemical structure of the iron complex in order to obtain a perfectly stable monolayer at the gas±water interface. Thus, we have synthesized a semi-fluorinated derivative of a spin crossover complex ( Fig. 1) that shows astonishing stability in the Langmuir film, allowing the formation of perfectly defined LB films of such a molecule. Using a recently developed method to perform magnetic measurements on a LB film with a SQUID susceptometer, [8] we were able to follow, for the first time, the spin crossover process in these multilayers. These measurements demonstrate the strong modification of the spin crossover phenomenon induced by the lamellar organization imposed by the LB technique. Following standard procedures, [9] the synthesis of the ligand [10] (denoted L) 4- (13,13,14,14,15,15,16,16,17,17,18,18, 18-tridecafluorooctadecyl)-4¢-methyl-2,2¢-bipyridine was carried out starting from commercially available 4,4¢-dimethyl-2,2¢-bipyridine and 13, 13,14,14,15,15,16,16,17,17,18, 18,18-tridecafluoroheptadecyl-1-bromide.[11] As already described in the literature, [12] the iron(II) complex [13] was obtained using a solution of Fe(NCS) 2 in methanol. The spin crossover process in the final compound was confirmed by magnetic susceptibility measurements (see below). The LB films were prepared by spreading a chloroform solution of the complex onto a 10 ±2 M KNCS aqueous solution. Compression isotherms yield a molecular area of ca. 63 A 2 at the collapse pressure. As already observed for a similar compound, this value is slightly smaller than that evaluated from the crystal structure [14] of Fe(bipy) 2 (NCS) 2 , where bipy stands for 2,2¢-bipyridine. Distortion of the complex due to the packing...

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“…One of the approaches is the modification of triazole ligands by substituting the long alkyl groups. Substituting the triazole complexes with long alkyl groups (octadecyl [13], 3-dodecyloxy propyl [14]) was reported. Another modification of the triazole ligand is the construction of the dendrimer by substituting it with the dendrons of a benzyl ether-type unit [14][15][16][17].…”

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confidence: 99%

Control of Spin-Crossover Phenomena in One-Dimensional Triazole-Coordinated Iron(II) Complexes by Means of Functional Counter Ions

et al. 2017

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Abstract:The spin-crossover (SCO) phenomenon between a high-spin and a low-spin state has attracted much attention in the field of materials science. Among the various kinds of SCO complexes, the triazole-bridged iron(II) polymeric chain system, [Fe(II)(R-trz) 3 ]X 2 ·xH 2 O (where trz is triazole and X is the anion), exhibiting the SCO phenomenon with thermal hysteresis around room temperature, has been extensively studied from the viewpoint of molecular memory and molecular devices. In connection with this system, we have controlled the SCO phenomenon according to the characteristic properties of counter ions. In the case of X being C n H 2n+1 SO 3 − , the spin transition temperature (T 1/2 ) increases with increasing the length (n) of the alkyl chain of the counter ion and saturates above n = 5, which is attributed to the increase in the intermolecular interaction of the alkyl chains of C n H 2n+1 SO 3 − , called the fastener effect. The hysteresis width of T 1/2 decreases with increasing n, showing the even-odd, also known as parity, effect. In the cases where X is toluenesulfonate (tos: CH 3 C 6 H 4 SO 3 − ) and aminobenzenesulfonate (abs: NH 2 C 6 H 4 SO 3 − ), T 1/2 and its hysteresis width vary drastically with the structural isomerism (ortho-, metha-, and para-substitution) of counter ions, which implies the possibility of photoinduced spin transition by means of the photoisomerization of counter ions. From this strategy, we have synthesized [Fe(II)(NH 2 -trz) 3 ](SP150) 2 ·2H 2 O (SP150 = N-alkylsulfonated spiropyran) and investigated the SCO phenomenon. Moreover, we have developed [Fe(II)(R-trz) 3 ]@Nafion films exhibiting spin transition around room temperature, where the Nafion membrane behaves as a counter anion as well as a transparent substrate, and investigated the photogenerated high-spin state below 35 K. The lifetime of the photogenerated high-spin state strongly depends on the intensity of irradiated light.

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Langmuir-Blodgett Films of Spin Transition Iron(II) Metalloorganic Polymers. 1. Iron(II) Complexes of Octadecyl-1,2,4-triazole

Cited by 65 publications

References 2 publications

Thermoreversible Gels as Magneto‐Optical Switches

Thermoreversible Gels as Magneto‐Optical Switches

First Magnetic Observation of a Spin Crossover in a Langmuir-Blodgett Film

Control of Spin-Crossover Phenomena in One-Dimensional Triazole-Coordinated Iron(II) Complexes by Means of Functional Counter Ions

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