New spin-crossover iron(III) complexes with large hysteresis effects and time dependence of their magnetism

Abstract

The new complexes [ FeL' ,] CIO, (H L' = tridentate Schiff base formed by 1 : 1 condensation of o-aminophenol and pyridine-2-carbaldehyde) and [FeL2,] NCS (H L2 = tridentate Schiff base formed by 1 : 1 condensation of 8-aminoquinoline and salicylaldehyde) were synthesized. The spincrossover behaviour between S = : and : which is dependent on temperature was observed for the solid complexes using variable-temperature 57Fe Mossbauer spectral and magnetic measurements.Both compounds show a pronounced hysteresis effect in the high spin + low spin transition. For [ FeL' ,] CIO,, sharp and strong Mossbauer absorptions were observed over the temperature range examined and the effective vibrating mass, Meff., was evaluated using the high-temperature approximation of the Debye model. The value for the low-spin isomer was larger than that for the high-spin isomer. The complex [ FeL2,J NCS when freshly recrystallized below 280 K is predominantly in a low-spin state. However, the magnetism at room temperature increases with time, spin-crossover behaviour is exhibited, and the magnetism is dependent on temperature, with a pronounced hysteresis loop of about 70 K at 286 K 10 d after preparation.

Photo‐Induced Spin Transition of Iron(III) Compounds with π–π Intermolecular Interactions

“…These differences are in the range of [37,[44][45][46] The bond length differences for iron(II) SCO compounds are also shown in Table 3. The values of Dr FeÀN are in the range of 0.18-0.27 ; those of Dr Fe-N for 2 ]Y systems (0.19 and 0.18 ) are in the range of those for iron(II) SCO compounds.…”

“…Selected bond lengths are listed in Table 2 and are consistent with those for typical HS ironA C H T U N G T R E N N U N G (III) compounds. [37,[44][45][46] Figure 4 shows that when 4·CH 2 Cl 2 is in the LS state, it crystallizes in the triclinic P1 space group. The structure of 4·CH 2 Cl 2 is also similar to that of 5·CH 2 Cl 2 .…”

“…The bond lengths of FeÀO1, FeÀO2, FeÀN1, FeÀN2, FeÀN3, and FeÀN4 for 2·H 2 O are given in Table 1 and are consistent with those typical for HS ironA C H T U N G T R E N N U N G (III) compounds. [37,[44][45][46] On the other hand, 2 ]Y systems (Y = NCS, NCSe). The structure of 5·CH 2 Cl 2 (LS) was revealed previously.…”

Temperature and pressure effects on the spin state of ferric ions in the [Fe(sal2-trien)][Ni(dmit)2] spin crossover complex

“…Combining SC and electrical conductivity was the aim of Dorbes et al [11] [12]. Analogously, similar properties have been studied on the salts of the [Fe(qsal) 2 ] + and Fe(R-salEen)] + complex cations as well [13][14][15][16][17][18][19].…”

Spin-Singlet Transition in the Magnetic Hybrid Compound from a Spin-Crossover Fe(III) Cation and π-Radical Anion

“…The spectrum at 293 K consisted of mainly a broad asymmetric quadrupole doublet with isomer shift (IS) of 0.307(16) mm·s −1 and quadrupole splitting (QS) of 0.91(2) mm·s −1 . As compared with the [Fe(qsal) 2 ] complexes in the literature [29,[38][39][40], the IS value is very similar to those of the HS [Fe(qsal) 2 ] species, whereas the QS value is larger than those of the HS species. This large QS value may arise from the distortion of a coordination octahedron.…”