Molecular multifunctional switching materials attract attention from both scientific and technological points of view due to the possibility of their application in molecular electronics. For example, such materials can be applied as active elements for switching, information storage, signal processing, molecular spintronics, and sensors. An important fact is that molecule-based bistable materials can change their states under the influence of different external stimuli. Spin crossover (SCO) complexes form a group of materials that can change their electronic configuration between the high- (HS) and low-spin (LS) states in response to the change of temperature or pressure, light irradiation, effect of guest molecules or substrates, magnetic field, etc. This effect of molecular bistability is mostly studied for iron(II) complexes. SCO if followed by a strong variation of most of the physical properties of these materials, such as magnetic, optical, electric, mechanical and other properties. Crystal structure of SCO complexes changes as well along the spin transition.
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.
