Temperature and pressure effects on the spin state of ferric ions in the [Fe(sal2-trien)][Ni(dmit)2] spin crossover complex

Abstract

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Thermo- and piezochromic properties of [Fe(hyptrz)]A2·H2O spin crossover 1D coordination polymer: Towards spin crossover based temperature and pressure sensors

“…Regarding this issue, very few attempts have been noticed to record the (p-T) phase diagram by using various detection techniques such as optical reflectivity [19][20][21][29][30][31], magnetic techniques [15][16][17][18][32][33][34], X-ray and neutron diffraction [35][36][37][38][39]. This lack of data could be explained by the difficulty to obtain small variations in the applied pressure in both loading and unloading processes, at variable temperatures.…”

Effects of Internal and External Pressure on the [Fe(PM-PEA)2(NCS)2] Spin-Crossover Compound (with PM-PEA = N-(2′-pyridylmethylene)-4-(phenylethynyl)aniline)

“…, where the application of 50 MPa induced a very large increase of the hysteresis width together with signs for an irreversible feature of these modifications [17]. Even though never clearly evidenced; other signs of irreversible effects of pressure were suspected in previous studies of SCO materials [10,19,48].…”

“…From the experimental point of view, many counter-examples have been reported so far [15]. For example, non-expected hysteresis broadening [16] as well as irreversible behaviors were reported for some compounds [10,17]. Even in a family of very similar complexes, a variety of high pressure behaviors can be observed.…”

Piezo‐ and Photo‐Crystallography Applied to Spin‐Crossover Materials

“…37 Elsewhere, since the reference case of [Fe(phen) 2 (NCS) 2 ], 6 expectation (v) has been confirmed in numerous investigations ( Fig. 20.1) 19,24,[38][39][40][41] but nonlinear behaviour has been reported as well in complexes that nonetheless clearly fulfil expectations (i)-(iii). 16,37 In the same manner, while the reversibility of pressure effects, expectation (vii), is often reported, 42, 43 some nonreversible effects have also been observed.…”

“…16,37 In the same manner, while the reversibility of pressure effects, expectation (vii), is often reported, 42, 43 some nonreversible effects have also been observed. 24,28 All attempts to rationalize the behaviour of SCO materials under pressure using comparative analysis of data finally came to the conclusion that the large diversity of situations is almost unpredictable. For instance, analysis of X-ray absorption spectra of eight iron mononuclear or polymeric complexes showed that about half of the investigated materials fulfilled the above expectations, but the other half showed clear differences, notably on (v).…”