Periodic Reporting for period 2 - SPINSWITCH (Multifunctional Spin Crossover Materials)
Reporting period: 2019-01-01 to 2021-12-31
A lot of work in the SCO research that has been done during the last 20 years is directed towards materials which can find some technological applications. The most outstanding examples of SCO application include contrast agents for tomography, thermal displays, routes towards information storage through dielectric bistability, photo-commutation of spin state, microactuators, etc.
Current SCO investigations are devoted to the development of controllable molecular systems, where (i) SCO of the materials can be routed by its another easily accessible property (sorption-desorption, phase behavior etc.) and/or where on contrary (ii) SCO controls some other functions of the material (mechanical, electric, optical, fluorescent properties, etc.). An interesting aspect is the use of SCO units as active elements of sensing materials that can switch in response to change in ambient conditions (pressure, temperature, humidity, chemical guests etc.). In some finely designed systems, the specific parts of SCO molecule can function as a receiver for the external stimuli which makes it an essential element of the multifunctional switching complex. This type of sensitivity allows precise control of the SCO parameters (temperature, abruptness, completeness), which is difficult to be achieved by other methods.
SPINSWITCH has several main goals: Investigation of new multifunctional materials, composites, hybrid mixtures where a controllable macroscopic event controls SCO properties; new metal-organic SCO Hofmann clathrates with sorption-desorption functionality; pressure effect study for prototyping pressure sensors; nanostructuration of SCO materials.
The work performed within the project as well included full physico-chemical characterization of new compounds and nanomaterials. Different types of experiments (SQUID magnetometry, single crystal and powder x-ray diffraction, Mössbauer, Raman, IR, UV-vis spectroscopies, optical microscopy and many other techniques) were performed in order to fully characterize physico-chemical parameters of new SCO compounds and materials. Complexes with pyridazines, naphtyridine, isothiocarbohydrazide, series of complexes with isomerizable ligands and those carrying long alkyl chains, new SCO cyanometallic, triazolic and triazolylborate nanoparticles and films were investigated.
The measurements of SCO compounds under pressure and elaboration of SCO pressure sensors were performed. We obtained data regarding SCO characteristics for the nanoparticles of iron-gold complex under pressure. Additionally, pressure effects on the electrical properties of bulk and nanosized samples of iron-gold complex were monitored. Pressure effects were also studied for Fe(II) triazolic nanoparticles and two polymorphs of one Fe(III) SCO complex. Besides, effects of pressure on the Fe(II) triazolic nanoparticles and electric properties of SCO thin films were investigated.
New multifunctional compounds are of particular interest for academic and industrial partners working in the growing field of molecular materials. These materials can find application in a new generation of molecule-based devices. We have developed compounds with unique characteristics of spin crossover and achieved extraordinary effects of the pressure on different SCO materials. Until the end of the project we plan to extend the set of new SCO materials for potential application and to propose a SCO pressure sensor.