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Nouveaux matériaux commutables à base de ligands polyazotés : extension aux systèmes polyfonctionnels

Abstract : This work is dedicated to the design and magnetostructural studies of new Fe(II) spin crossover (SCO) systems, in particular those involving the functionalized macrocycle and the 4-R-1,2,4-triazole triazole ligands.The principal objective concerns the study of the substitution and solvent effects on the SCO characteristics. In the first step, we have studied the solvent and the counter-ion effects, on the SCO behavior, in the series [Fe(L2)](X).nH2O (L2 = 1,8-bis(2’-pyridylméthyl)-1,4,8,11-tétraaza-cyclotétradécane, X = 2(tcm)- = 2[C(CN)3]-, n = 2 (1) ; X = [Ni(CN)4]2-, n = 1 (2) ; X = (BF4)-, n = 1 (3)), based on the macrocycles ligands. We have clearly shown in this study that the strong cooperative effects are mediated by the water solvent molecules and the counter-ions involved in the hydrogen bonding in the crystal packing. In the second step, the use of the 4-R-1,2,4-triazole fuctionalized triazole ligands led us to two original switchable systems: (i) the first one concerns the trinnuclear complex of formulae Fe3(furmetrz)6(tcnsme)6] (furmetrz = 4-(furan-2-ylmethyl)-1,2,4-triazole; (tcnsme)- = 1,1,3,3-tetracyano-2- thiométhylpropenide), for which the magnetic study reveals a two-step SCO transition and a LIESST effects with a T(LIESST) of 58 K. Examination of the intermolecular interactions in this complex and other parent trinuclear systems exhibiting complete one-step spin transition, revealed that the presence of the two-step behavior is clearly favored by strong inter-trimer interactions along the trimer axis; (ii) the second system the design and syntheses of to several series of polyfunctional materials exhibiting SCO and luminescent behaviors. In this new way, the most significant result concerns an original discrete Fe(II) complex of formulae [Fe(naphtrz)6](tcnsme)2.4CH3CN (naphtrz = N-(1,2,4-triazol-4-yl)-1,8-naphthalimide), for which the magnetic and photoluminescent studies showed that this material exhibits synergetic SCO and luminescent behaviors. This proves the possibility to control the luminescent properties through simple external perturbations such as temperature, pressure, light irradiation,… In addition, beyond the fundamental aspect, this work open new innovative perspectives for the use of such original materials as sensors or standards of temperature.
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Bouabdellah Benaicha. Nouveaux matériaux commutables à base de ligands polyazotés : extension aux systèmes polyfonctionnels. Autre. Université de Bretagne occidentale - Brest, 2017. Français. ⟨NNT : 2017BRES0073⟩. ⟨tel-02003578⟩

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