Spin transition in a magnetic Langmuir-Blodgett film

Ruaudel‐Teixier, A.; Barraud, A.; Coronel, P.; Kahn, O.

doi:10.1016/0040-6090(88)90052-1

Cited by 39 publications

(18 citation statements)

References 8 publications

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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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“…A wide variety of film formation procedures have been developed, based on the direct usage of the metal alkoxide, the pre-hydrolyzed monomer [4] or colloidal metal hydroxides. [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.…”

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“…This separation is made possible because the rate of hydrolysis is fast under acidic conditions, while that of the condensation is enhanced in alkaline solutions. [5,9,10,11] According to the methodology we developed, a local increase of the pH near an electrode surface is induced by applying a constant negative potential to the electrode surface. The increase of hydroxyl ions, which act as a catalyst in the condensation process, results in the controllable sol-gel film deposition.…”

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

et al. 1999

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“…This included the discovery of several new examples of SCO compounds [3,[9][10][11], the explanation of different types of SCO profiles [4,12] and the modification of SCO compounds to increase cooperativity and to direct their application into materials science [13]. Scientists have developed SCO networks [14][15][16], frameworks [17][18][19], gels [20][21][22], liquid crystals [23][24][25], nanoparticles and nanocrystals [26][27][28][29], nanowires [30], thin films [31][32][33] and have also applied patterning techniques to fabricate SCO devices [34]. Among complexes displaying SCO, [Fe(salEen) 2 ] + derivatives (salEen = N-ethyl-N-(2-aminoethyl)salicylaldiminate) are known to undergo thermal SCO sensitive to unit cell contents and supramolecular packing in the crystal [35].…”

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Solution and solid state properties of Fe(III) complexes bearing N-ethyl-N-(2-aminoethyl)salicylaldiminate ligands

Martinho

Vicente

Realista

et al. 2014

Journal of Organometallic Chemistry

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“…3 Iron(II) complexes of N 4 -substituted-3,5-di(2-pyridyl)-4H-1,2,4-triazoles (Rdpt, Fig. 1 [10][11][12][13][14][15] an attractive feature that allows us to take our first tentative steps towards the long term goal of inclusion of SCO complexes into functional devices. C 16 dpt was made according to our general procedure.…”

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