Preparation and Radical Oligomerization of anFe(II) Complex without Loss of Spin-Crossover Properties

Two‐Step Spin Transition in a 1D FeII 1,2,4‐Triazole Chain Compound

“…[25][26][27][28][29] This is illustrated, for example, in the mononuclear Fe II complexes [Fe(2-pic) 3 ]Cl 2 ·EtOH (2-pic = 2-picolylamine) [30] and Fe 4,7,10)],i nw hich 5-NO 2 -sal-N(1,4,7,10)i sahexadentate ligand obtained from the condensation of 5-NO 2 -salicylaldehyde with 1,4,7,10-tetraazadecane. In the case of mononuclear complexes,t he intermediate phase at the plateau region results from symmetry breaking and al ong-or short-range ordering of an intermediate spin state (HS-LS).…”

“…[1][2][3] Although the origin of the SCO phenomenon is molecular,i ts cooperative manifestation depends on an efficient coupling between SCO centers in the crystal lattice through covalent and/ors upramolecular interactions. [6][7][8] This family of materials display aw ider ange of thermally-induced SCO behaviors ranging from complete, [9] to incomplete transitions, [10][11][12] gradual, [13][14][15] to abrupt, [16,17] and hysteretic ones, [16][17][18][19][20] the latter being important for potentiala pplications in display devices and sensors. [4,5] In particular, the family of Fe II 1D chains with 4R-1,2,4-triazole has been very much studied.…”

Rapid Cooling Experiments and Use of an Anionic Nuclear Probe to Sense the Spin Transition of the 1D Coordination Polymers [Fe(NH2trz)3]SnF6⋅n H2O (NH2trz=4‐amino‐1,2,4‐triazole)

“…Keywords: cooperative phenomena · coordination polymers · lattice dynamics · Moessbauer spectroscopy · spin transition served for chain compounds with bulky substituents on the 4-position of the triazole. [13][14][15] [FeA C H T U N G T R E N N U N G (Htrz) 2 trz]A C H T U N G T R E N N U N G (BF 4 ) (Htrz = 4H-1,2,4-triazole; trz = 1,2,4-triazolato) [16,17] and [FeA C H T U N G T R E N N U N G (NH 2 trz) 3 ]A C H T U N G T R E N N U N G (NO 3 ) 2 (NH 2 trz = 4-amino-1,2,4-triazole) [18] are important examples of this family of materials because they exhibit a hysteretic ST % 40 [17] and % 35 K, [18,19] wide, respectively. A structural modification from a linear conformation in the low-spin (LS) state to a zigzag one in the high-spin (HS) state was first proposed to account for the absence of long-range ordering in X-ray absorption experiments (EXAFS, wide-angle X-ray scattering (WAXS)) in the HS state for these materials.…”

Triazole‐Based One‐Dimensional Spin‐Crossover Coordination Polymers

“…Those used so far for the preparation of 4‐substituted 1,2,4‐triazoles in SCO‐related studies, depicted in Scheme , are the transamination of N , N ′‐dimethylformamide azine with primary amines,34 the reaction of diformylhydrazine with a primary amine,35 the reaction of an orthoformate with monoformylhydrazine to give an N ‐alkoxymethylene‐ N ′‐formylhydrazine, which is then treated with the primary amine of choice,36 and the functionalisation of the amino group of 4‐amino‐1,2,4‐triazole. Substituents can also introduced on the 4‐position by reaction of a 1‐substituted‐1,2,4‐triazole with an alkylbromide 37. Overall, the number of substituents that have so far been used is still limited (Schemes and ), but their variable types clearly indicate almost any chemical function could be grafted to these polymeric chains, simply by designing a proper substituent/reaction path.…”

“…Processing of these SCO triazole‐based solids into composite materials with more manipulability may be necessary for technological applications; this has first been done by dispersing into a resin or an organic polymeric matrix 51. A polymerisable methacrylate substituent was also introduced and the coordination polymers were thus used as constituent of the organic polymer backbone, although the transitions were then very gradual 37. Other types of phases, such as gels or liquid crystals, seemed to be good alternatives to process the SCO into a technologically useful material, and the triazole‐based coordination polymers have again been at the centre the related research activity.…”