Calorimetric measurements of diluted spin crossover complexes [FexM1−x(btr)2(NCS)2]·H2O with MII=Zn and Ni

Rotaru, Aurelian; Dîrtu, Marinela M.; Enachescu, Cristian; Tanasa, Radu; Linarès, Jorge; Stancu, Alexandru; Garcia, Yann

doi:10.1016/j.poly.2009.04.046

Cited by 40 publications

(49 citation statements)

References 29 publications

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“…[12,13,30,31] An exception is T c 2 ȇ, which increases dramatically between x = 0.89 and 0.76. This is a rare observation, which leads to the quick disappearance of the IP with x = 0.76.…”

Section: Discussionmentioning

confidence: 99%

“…We hypothesize that this is the reason why the crystal structure of the diluted samples (a) to (i) changes at zinc content higher than 0.47, and why mixed single crystals could not be obtained. [26] Dilution studies were achieved on two-step SCO compounds [27] or one-step SCO compound including hysteretic cycles, [17,[28][29][30] but to the best of our knowledge this report is the first metal-dilution study on a two-step SCO Fe II system with two hysteresis loops. For compound 1, cooperativity is mediated mainly by means of intermolecular N-H···S hydrogen-bonding networks.…”

Section: Discussionmentioning

confidence: 99%

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Effect of Metal Dilution on the Thermal Spin Transition of [Fe_xZn_1–x(bapbpy)(NCS)₂]

et al. 2013

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This study reports on the effects of zinc dilution on the structure and magnetic properties of the mononuclear two-step spin-crossover compound [Fe(bapbpy)(NCS) 2 ] (1; bapbpy = N6, N6Ј-di(pyridin-2-yl)-2,2Ј-bipyridine-6,6Ј-diamine). According to powder X-ray diffraction and infrared spectroscopy, the phase of compound 1 is retained in the zincdiluted samples when x Ͼ 0.53. At higher dilutions (i.e., when x Ͻ 0.53), the phase of compound 3 gradually takes

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“…[12,13,30,31] An exception is T c 2 ȇ, which increases dramatically between x = 0.89 and 0.76. This is a rare observation, which leads to the quick disappearance of the IP with x = 0.76.…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Effect of Metal Dilution on the Thermal Spin Transition of [Fe_xZn_1–x(bapbpy)(NCS)₂]

et al. 2013

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“…The heating and cooling rates were fixed at 10 K min −1 . Temperatures and enthalpies were calibrated over the temperature range of interest (298–400 K) using the solid-liquid transitions of pure In (99.99%) [33], and the crystal-crystal transitions of pure cyclopentane (≥99%) [34], over the range 78–298 K. Scanning electron microscopy (SEM) was performed using a Gemini Digital Scanning Microscope 982 with 1 kV accelerating voltage with an aluminum sample holder.…”

Section: Methodsmentioning

confidence: 99%

Spin Transition Sensors Based on β-Amino-Acid 1,2,4-Triazole Derivative

Dîrtu

Schmit

Naik

et al. 2011

IJMS

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A β-aminoacid ester was successfully derivatized to yield to 4H-1,2-4-triazol-4-yl-propionate (βAlatrz) which served as a neutral bidentate ligand in the 1D coordination polymer [Fe(βAlatrz)3](CF3SO3)2·0.5H2O (1·0.5H2O). The temperature dependence of the high-spin molar fraction derived from 57Fe Mossbauer spectroscopy recorded on cooling below room temperature reveals an exceptionally abrupt single step transition between high-spin and low-spin states with a hysteresis loop of width 4 K (Tc↑ = 232 K and Tc↓ = 228 K) in agreement with magnetic susceptibility measurements. The material presents striking reversible thermochromism from white, at room temperature, to pink on quench cooling to liquid nitrogen, and acts as an alert towards temperature variations. The phase transition is of first order, as determined by differential scanning calorimetry, with transition temperatures matching the ones determined by SQUID and Mössbauer spectroscopy. The freshly prepared sample of 1·0.5H2O, dried in air, was subjected to annealing at 390 K, and the obtained white compound [Fe(βAlatrz)3](CF3SO3)2 (1) was found to exhibit a similar spin transition curve however much temperature was increased by (Tc↑ = 252 K and Tc↓ = 248 K). The removal of lattice water molecules from 1·0.5H2O is not accompanied by a change of the morphology and of the space group, and the chain character is preserved. However, an internal pressure effect stabilizing the low-spin state is evidenced.

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“…Powder X-ray diffraction patterns were recorded on aS iemens D5000 counter diffractometer working with Cu Ka radiation and operating at room temperature. 99 %), [82] over the range 78-298 K. SEM was performed using aG emini Digital Scanning Microscope 982 with 1kV accelerating voltage with an aluminium sample. 57 Fe Mçssbauer spectra were recorded in transmission geometry over the temperature range (78-300 K) with ac onventional Mçssbauer spectrometer equipped with a 57 Co(Rh) radioactive source operating at room temperature.…”

Section: Physical Measurementsmentioning

confidence: 99%

Two‐Step Spin Transition in a 1D Fe^II 1,2,4‐Triazole Chain Compound

Dîrtu

Schmit

Naik

et al. 2015

Chemistry A European J

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A thermochromic 1D spin crossover coordination (SCO) polymer [Fe(βAlatrz)3](BF4)2⋅2 H2O (1⋅2 H2O), whose precursor βAlatrz, (1,2,4-triazol-4-yl-propionate) has been tailored from a β-amino acid ester is investigated in detail by a set of superconducting quantum interference device (SQUID), (57)Fe Mössbauer, differential scanning calorimetry, infrared, and Raman measurements. An hysteretic abrupt two-step spin crossover (T1/2(↓) = 230 K and T1/2(↑) = 235 K, and T1/2(↓) = 172 K and T1/2(↑) = 188 K, respectively) is registered for the first time for a 1,2,4-triazole-based Fe(II) 1D coordination polymer. The two-step SCO configuration is observed in a 1:2 ratio of low-spin/high-spin in the intermediate phase for a 1D chain. The origin of the stepwise transition was attributed to a distribution of chains of different lengths in 1⋅2 H2O after First Order Reversal Curves (FORC) analyses. A detailed DFT analysis allowed us to propose the normal mode assignment of the Raman peaks in the low-spin and high-spin states of 1⋅2 H2O. Vibrational spectra of 1⋅2 H2O reveal that the BF4(-) anions and water molecules play no significant role on the vibrational properties of the [Fe(βAlatrz)3](2+) polymeric chains, although non-coordinated water molecules have a dramatic influence on the emergence of a step in the spin transition curve. The dehydrated material [Fe(βAlatrz)3](BF4)2 (1) reveals indeed a significantly different magnetic behavior with a one-step SCO which was also investigated.

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Calorimetric measurements of diluted spin crossover complexes [FexM1−x(btr)2(NCS)2]·H2O with MII=Zn and Ni

Cited by 40 publications

References 29 publications

Effect of Metal Dilution on the Thermal Spin Transition of [Fe_xZn_1–x(bapbpy)(NCS)₂]

Effect of Metal Dilution on the Thermal Spin Transition of [Fe_xZn_1–x(bapbpy)(NCS)₂]

Spin Transition Sensors Based on β-Amino-Acid 1,2,4-Triazole Derivative

Two‐Step Spin Transition in a 1D Fe^II 1,2,4‐Triazole Chain Compound

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Calorimetric measurements of diluted spin crossover complexes [FexM1−x(btr)2(NCS)2]·H2O with MII=Zn and Ni

Cited by 40 publications

References 29 publications

Effect of Metal Dilution on the Thermal Spin Transition of [FexZn1–x(bapbpy)(NCS)2]

Effect of Metal Dilution on the Thermal Spin Transition of [FexZn1–x(bapbpy)(NCS)2]

Spin Transition Sensors Based on β-Amino-Acid 1,2,4-Triazole Derivative

Two‐Step Spin Transition in a 1D FeII 1,2,4‐Triazole Chain Compound

Contact Info

Product

Resources

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Effect of Metal Dilution on the Thermal Spin Transition of [Fe_xZn_1–x(bapbpy)(NCS)₂]

Effect of Metal Dilution on the Thermal Spin Transition of [Fe_xZn_1–x(bapbpy)(NCS)₂]

Two‐Step Spin Transition in a 1D Fe^II 1,2,4‐Triazole Chain Compound