Preserving the spin transition properties of iron-triazole coordination polymers within silica-based nanocomposites

Abstract

Preserving the spin transition properties of iron-triazole coordination polymers within silica-based nanocomposites †T. Coradin * a and C. Roux* a One dimensional iron(II) coordination polymers formed from 1,2,4-triazole bridging ligands are a unique class of spin-crossover materials (SCO). The integration of those coordination polymers into devices for practical applications remains a major challenge. Using a nanocomposite approach based on the control of coordination polymer interactions with chemically engineered silica particles, we show that we can achieve in situ gelation, while preserving the SCO properties of the solid state. Tuning the interface between the two phases of a composite provides a unique way to synergistically adjust the material's structure and the cooperativity associated with its transition properties. The strategy described here should allow for bridging the gap between soft and crystalline functional inorganic materials.

A flexible polymer–nanoparticle hybrid material containing triazole-based Fe(ii) with spin crossover properties for magneto-optical applications

“…We have shown that the presence of NPs and the subtle balance between the three interacting components is a unique way to control the SCO properties of the gel. 36 In this case, transition temperatures (heating T ↗ and cooling T ↘ ) have been shown to increase with increasing SiO 2 content ( Fig. S1 and S2 †).…”

“…Sulfonate functionalization of the surface proceeded through a previously described two-step procedure. 36 Zeta potential and size distribution are systematically measured using a Malvern Zetasizer Nano ZS90 instrument giving a negative zeta potential of ca. −53 mV in 0.5 M acetic acid ( pH 2.5) and a hydrodynamic diameter of ca.…”

“…Preparation of the Si-SCO composite. As previously described, 36 140 mg of silica NPs (200 nm in diameter) were suspended in 0.75 mL of an ethylene glycol : water mixture (v/v 9 : 1) under sonication for 45 minutes. 27.8 mg of iron sulfate heptahydrate (FeSO 4 •7H 2 O, 0.1 mmol) (Sigma-Aldrich, 99%) were added to the suspension and heated at 50°C for 30 minutes with 20 mg of ascorbic acid.…”

“…The silica-free SCO polymer was prepared in an ethylene glycol : water mixture (v/v 9 : 1) as previously described. 36 To this suspension, 10 mL ethanol was added to induce the formation of a precipitate. The mixture was centrifuged, washed 3 times with 10 mL ethanol and the precipitate was recovered before drying under ambient air.…”

“…[20][21][22][23][24][25][26] Supramolecular gels have also been successfully obtained based on the alkyl functionalization of triazole ligands and/or counter-anions, [27][28][29][30][31][32][33] with few examples using hydrophilic ligands 34,35 or a polyol synthetic route. 36 The latter approach may be of particular interest as it should extend the possibility of obtaining gels from a broad diversity of SCO systems reported in the literature. In particular, we have recently used this polyol route combined with a hybrid approach.…”