Mosaicity and structural fatigability of a gradual spin-crossover single crystal

The present Letter introduces a novel approach to test the efficiency of spin crossover materials with regard to structural fatigability. By measuring single-crystal mosaicity, structural fatigability is evidenced in a gradual SCO iron compound. The non fatigability of the analogue non-SCO zinc compound demonstrates the role of SCO in such observation. The mosaicity strongly increases during the first cycles. It is therefore clearly shown that fatigability can affect non-cooperative SCO systems. Magnetic properties appear however not altered by the observed structural fatigability which is thus related to mechanical aspects of SCO

Spin crossover materials evaporated under clean high vacuum and ultra-high vacuum conditions: from thin films to single molecules

We report clean evaporation under ultra-high vacuum conditions of two spin crossover materials, yielding either microcrystallites or homogeneous thin films. Magnetic and photomagnetic studies show that thermal and light-induced spin crossover properties are preserved. Preliminary STM imaging of sub-monolayers indicates that the deposited molecules remain intact on the surface

observation of a phase transition of a single sub-micrometer spin transition particle

we developed a DIC microscope to measure the termo and photocommutation of a single particle. first commutations are reporter

Thermal spin crossover behaviour of two-dimensional Hofmann-type coordination polymers incorporating photoactive ligands

Two spin crossover (SCO)-active 2D Hofmann-type framework materials, [Fe(3-PAP)2Pd(CN)4] (A) and [Fe(4-PAP)2Pd(CN)4] (B) containing the photoactive azo-benzene-type ligands 3-phenylazo-pyridine (3-PAP) and 4-phenylazo-pyridine (4-PAP) were prepared. These materials form non-porous Hofmann-type structures whereby 2D [FeIIPd(CN)4] grids are separated by 3- or 4-PAP ligands. The iron(ii) sites of both materials (A and B) undergo abrupt and hysteretic spin transitions with characteristic transition temperatures T1/2↓,↑: 178, 190 K (ΔT: 12 K) and T1/2↓,↑: 233, 250 K (ΔT: 17 K), respectively. Photo-magnetic characterisations reveal light-induced excited spin state trapping (LIESST) activity in both A and B with characteristic T(LIESST) values of 45 and 40 K. Although both free ligands show trans- to-cis isomerisation in solution under UV-irradiation, as evidenced via absorption spectroscopy, such photo-activity was not observed in the ligands or complexes A and B in the solid state. Structural analysis of a further non-SCO active isomer to B, [Fe(4-PAP)2Pd(CN)4]·1/2(4-PAP) (B·(4-PAP)), which contains free ligand in the pore space is reported

observation of a phase transition of a single sub-micrometer spin transition particle

we developed a DIC microscope to measure the termo and photocommutation of a single particle. first commutations are reporter

Discrete FeII spin-crossover complexes of 2,2'-dipyridylamino- substituted s-triazine ligands with phenoxo, cyanophenoxo and dibenzylamino functionalities

Four 2,2′-dipyridylamino-s-triazine-substituted ligands, each of which incorporate different aromatic substituents (phenoxo, 4-CN-phenoxo and benzylamino) with different degrees of bulk and flexibility, have been formed and incorporated into a number of mononuclear FeII complexes of type trans-[FeII(L)2(NCX)2]·solvent (in which X = S, Se and BH3). These ligands were designed to promote π–π stacking between complexes. The complexes reported have been comprehensively characterised using single-crystal diffraction techniques in combination with magnetic susceptibility measurements. Light-induced excited spin-state trapping (LIESST) measurements have been performed on selected complexes. Light irradiation has shown the occurrence of a reversible photoswitching process at low temperature

observation of a phase transition of a single sub-micrometer spin transition particle

we developed a DIC microscope to measure the termo and photocommutation of a single particle. first commutations are reporter

observation of a phase transition of a single sub-micrometer spin transition particle

we developed a DIC microscope to measure the termo and photocommutation of a single particle. first commutations are reporter

Solvate-dependent spin crossover and exchange in cobalt(II) oxazolidine nitroxide chelates

Two oxazolidine nitroxide complexes of cobalt(II), [Co(II)(L(*))2](B(C6F5)4)2*CH2Cl2 (1) and [Co(II)(L(*))2](B(C6F5)4)2*2Et2O (2), where, L(*) is the tridentate chelator 4,4-dimethyl-2,2-bis(2-pyridyl)oxazolidine N-oxide, have been investigated by crystallographic, magnetic, reflectivity, and theoretical (DFT) methods. This work follows on from a related study on [Co(II)(L(*))2](NO3)2 (3), a multifunctional complex that simultaneously displays magnetic exchange, spin crossover, and single molecule magnetic features. Changing the anion and the nature of solvation in the present crystalline species leads to significant differences, not only between 1 and 2 but also in comparison to 3. Structural data at 123 and 273 K, in combination with magnetic data, show that at lower temperatures 1 displays low-spin Co(II)-to-radical exchange with differences in fitted J values in comparison to DFT (broken symmetry) calculated J values ascribed to the sensitive influence of a tilt angle (θ) formed between the Co(dz(2)) and the trans-oriented O atoms of the NO radical moieties in L(*). Spin crossover in 1 is evident at higher temperatures, probably influenced by the solvate molecules and crystal packing arrangement. Complex 2 remains in the high-spin Co(II) state between 2 and 350 K and undergoes antiferromagnetic exchange between Co-radical and radical-radical centers, but it is difficult to quantify. Calculations of the magnetic orbitals, eigenvalue plots, and the spin densities at the Co and radical sites in 1 and 2 have yielded satisfying details on the mechanism of metal-radical and radical-radical exchange, the radical spins being in π*NO orbitals