Detailed studies of impacts on the new 1D spin transition polymer [Fe(hyetrz) 3 ]I 2 •0.5EtOH have been performed under several controlled contact pressures, showing for high energy values a color change of the compound and allowing a visual detection of the spin transition from high-spin to low-spin states. By performing detailed investigations on freshly impacted samples, using spectroscopic diffuse optical reflectivity, we could follow the variation of the optical spectra as a function of the energy of the impact. The meticulous analysis of the obtained spectra allowed us to establish an absorption peak at 550 nm whose intensity and position well correlate to the energy of the impact. This concept provides a reliable method of measuring the energy of a chock even if the sample does not change its color so much in the visible range. This might be of high importance in several civil security applications, like transportation of artwork or other fragile valuable objects or even in the evaluation of the degree of alteration of a material after a collision.
We have investigated the suitability of using the 1D spin crossover coordination polymer [Fe(4-(2′-hydroxyethyl)-1,2,4-triazole)3]I2·H2O, known to crossover around room temperature, as a pressure sensor via optical detection using various contact pressures up to 250 MPa. A dramatic persistent colour change is observed. The experimental data, obtained by calorimetric and Mössbauer measurements, have been used for a theoretical analysis, in the framework of the Ising-like model, of the thermal and pressure induced spin state switching. The pressure (P)-temperature (T) phase diagram calculated for this compound has been used to obtain the P-T bistability region.
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