Switchable molecule-based materials for micro- and nanoscale actuating applications: Achievements and prospects

Crystallinity and Microstructural Versatility in the Spin‐Crossover Polymeric Material [Fe(Htrz)2(trz)](BF4)

“…[13] It has also been shown that the crystal structure remains the same for particle sizes in the range of 10 nm to 1.3 μm. [13] Crystallographic studies on the physical scale of particles, to be specific, the coherent domain size, are still very rare in the SCO field, even though microstructural features are sometimes suspected of being a potential key point for under-nity of the material by doubling the coherent domain size, which may open a route to regenerating this system after the reported mechanical fatigue it undergoes after suffering numerous SCO cycles. In addition, the correlation between the length of the coherent domain and the SCO temperature shows that the longer the domains, that is, the longer the iron chains, the higher the SCO temperatures.…”

“…This is of importance because the width of the cylinder corresponds to interchain interactions, which are also known to account for the cooperativity of this material. [10,13] To sum up, the cylindrical morphology is largely predominant and may be considered a reproducible feature, but the diversity of lengths, notably, shows the versatility of the microstructures of the [Fe(Htrz) 2 (trz)](BF 4 ) powders.…”

“…[4][5][6][7][8][9][10] Its potential interest has been quoted in fields as diverse as X-chromic pigments, mechanical actuators, and optical sensors. [11][12][13] Note that this material can show various forms, not all clearly identified, [10] but the present work deals with the most popular form, which shows the most stable hysteresis and is now clearly identified as [Fe(Htrz) 2 (trz)](BF 4 ). The structural investigation of [Fe(Htrz) 2 (trz)](BF 4 ) was limited until the recent determination of its crystal structure by means of X-ray diffraction.…”

The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

“…However, SCO in different compounds also leads to changes in color; fluorescence; conductivity (in the bulk or at the single molecule level); and/or dielectric constant [15]. It can also lead to a measurable mechanical response in a solid sample [21]. SCO materials can be fabricated at the nanoscale, retaining their switching functionality at least partially in the 10 1 -10 2 nm size regime [22].…”

Structures and spin states of crystalline [Fe(NCS)2L2] and [FeL3]2+complexes (L = an annelated 1,10-phenanthroline derivative)

“…[1][2][3] A spin-transition causes measurable changes to the physical properties of a molecular solid, including its colour, 4 magnetic moment, 4 conductivity, 5 dielectric constant 6 and particle size and shape. 7 Moreover, in addition to their own intrinsic functionality, spin-transition molecules can be auxiliary switching centers 8 in multifunctional fluorescent, 9 semiconducting 10 and magnetic materials. 11 The spin-transition phenomenon also functions in soft materials 12 and at the nanoscale, 13 and the relationship between particle size and switching functionality is now quite well understood.…”