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. 2022 Feb 11;27(4):1213.
doi: 10.3390/molecules27041213.

Synthesis and Characterization of [Fe(Htrz)2(trz)](BF4)] Nanocubes

Alexis A Blanco  1 , Daniel J Adams  2 , Jason D Azoulay  2 , Leonard Spinu  1 , John B Wiley  1
Affiliations

Synthesis and Characterization of [Fe(Htrz)2(trz)](BF4)] Nanocubes

Alexis A Blanco et al. Molecules. .

Erratum in

Abstract

Compounds that exhibit spin-crossover (SCO) type behavior have been extensively investigated due to their ability to act as molecular switches. Depending on the coordinating ligand, in this case 1H-1,2,4-triazole, and the crystallite size of the SCO compound produced, the energy requirement for the spin state transition can vary. Here, SCO [Fe(Htrz)2(trz)](BF4)] nanoparticles were synthesized using modified reverse micelle methods. Reaction conditions and reagent ratios are strictly controlled to produce nanocubes of 40-50 nm in size. Decreases in energy requirements are seen in both thermal and magnetic transitions for the smaller sized crystallites, where, compared to bulk materials, a decrease of as much as 20 °C can be seen in low to high spin state transitions.

Keywords: SQUID; Tergitol NP9; nanoparticles; reverse micelle; size study; spin crossover; thermal hysteresis; transmission electron microscope.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Left, triazole ligand with nitrogens at the 1, 2, and 4 positions. Right, triazole complex showing the N1, N2 triazole triple bridge that supports the 1D coordination chains of the structure. (R is used to simplify image, and represents bridging nitrogen (4) as shown in the 1,2,4-triazole ligand on the left.)
Figure 2
Figure 2
[Fe(Htrz)2(trz)](BF4)] nanocubes synthesized using the optimal method developed by adaptation of a known reverse micelle approach. (A,B) are from the same sample and separate cubic particles can be seen, along with some agglomerated particles. (C) is the particle’s distribution for the average diameter of the nanoparticles obtained in (A,B).
Figure 3
Figure 3
TEM images of particles that were obtained when precursors were separated within different vials and stirred for 5 min, Reaction 5. Both (A,C) are samples that were conducted with the same reaction conditions. (B,D) are average lengths and widths, respectively.
Figure 4
Figure 4
Observed XRD pattern for [Fe(Htrz)2(trz)](BF4)] (top, blue) versus the simulated low spin reference pattern (bottom, orange). Broad diffraction peaks are observed, consistent with the nanoparticle nature of the sample. Reference pattern calculated from published data [14].
Figure 5
Figure 5
TGA and DSC data obtained for [Fe(Htrz)2(trz)](BF4)] as it was thermally cycled 3 times in an inert atmosphere. (A) DSC data on the phase changes as the sample is heated from room temperature to 160 °C for a total of 3 cycles. (B) TGA data on the weight changes that correspond to the 3 thermal cycles (marked 1, 2, and 3 next to heating and cooling transition temperatures). Thermal hysteresis can be seen in (A) between the exothermic (high to low spin state transition) and endothermic events (low to high spin transitions).
Figure 6
Figure 6
TGA and DSC data on [Fe(Htrz)2(trz)](BF4)] bulk samples that did not have any Tergitol NP9 present in the synthesis. (A) DSC data show higher temperatures for the transition from low spin to high spin when compared to nanoparticles in all three thermal cycles. (B) Weight loss for the bulk sample shows that less weight is lost in the three thermal cycles when compared to the nanoparticles.
Figure 7
Figure 7
SQUID data obtained for [Fe(Htrz)2(trz)](BF4)] nanocubes using Tergitol-NP surfactant. Sample was held under a constant magnetic field of 1000 Oe. Initial transition from low to high spin state can be seen starting at 355 K. High to low spin transition occurred at 345 K which then stabilized at 335 K.
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