Spin-crossover behavior of neutral iron(iii) complexes with salicylaldehyde thio-, seleno- and semicarbazone ligands: experiment and theoretical analysis

Abstract

A novel neutral complex [FeIII(Hsemsal)(semsal)]·3H2O was synthesized and its magnetic properties, and crystal and electronic structures were studied.

First crystal structure of an Fe(iii) anionic complex based on a pyruvic acid thiosemicarbazone ligand with Li+: synthesis, features of magnetic behavior and theoretical analysis

“…Previously, a similar conclusion was made for the salicylaldehyde thio-, seleno-and semicarbazone ligands in this study. 56 As mentioned above (see magnetic part), the lithium cation with iron(III) anionic spin crossovers (Li[Fe(thsa) 2 ]•2H 2 O and Li [Fe(5Br-thsa) 2 ]•H 2 O) leads to the shift in the T 1/2 -parameter in the high-temperature region, i.e. the stabilization of the LS state.…”

High-Temperature Spin Crossover in FeIII N4O2 Complexes Incorporating an [R-sal2323] Backbone

“…The literature in SCO is dominated by Fe II compounds, which is due in part to its easily distinguished spin states, ,, although Fe III also has been well-studied. ,,, Recent studies have highlighted magnetostructural dependence arising from the delicate interplay of substituent, anion and solvent selection on the exhibition and behavior of SCO in Fe III mononuclear complexes. − Practically, Fe III is a good candidate for use in devices, because it is not susceptible to oxidation, and its 3d 5 electron configuration gives rise to a strong magnetic signal in the HS state ( S = 5/2), with a comparatively weak signal in LS ( S = 1/2) . Coordination spheres that have been shown to favor SCO in Fe III compounds include N 2 O 2 S 2 , N 3 O 2 S, N 5 O , and N 6 , although the most commonly reported example is N 4 O 2 . ,, One ligand archetype which affords this coordination environment is the H 2 Salen family, which has been shown to enable SCO in Fe III and other metals. ,− Studies have investigated the effect of the tetraamine backbone length on the spin state. , Common variations of the tetraamine backbone include the following: sal 2 222, sal 2 232, and sal 2 323 (Figure ). Various Fe III complexes of sal 2 222, sal 2 232, and sal 2 323 have been shown to exhibit SCO behavior, with the latter most often residing in LS up to ambient temperatures, with a few examples of SCO above room temperature. ,,, …”

“…17 Coordination spheres that have been shown to favor SCO in Fe III compounds include N 2 O 2 S 2 , 26 N 3 O 2 S, 27 N 5 O 18,28 and N 6 , 29 although the most commonly reported example is N 4 O 2 . 7,17,30 One ligand archetype which affords this coordination environment is the H 2 Salen family, which has been shown to enable SCO in Fe III and other metals. 18,30−35 Studies have investigated the effect of the tetraamine backbone length on the spin state.…”

Push and Pull Effect of Methoxy and Nitro Groups Modifies the Spin-State Switching Temperature in Fe(III) Complexes

“…Indeed, SCO and spin transition behavior have been studied in transition-metal complexes where the metal ion has an electronic configuration from d 4 to d 9 . Most Fe­(II) SCO complexes contain a N 6 surrounding with a moderate ligand field environment while with Fe­(III) SCO complexes contain mainly N 4 O 2 , N 2 O 4 , or N 2 O 2 S 2 surroundings with moderate or slightly weaker ligand field environments compared to Fe­(II) systems . While many Fe­(II) complexes are not air-stable, the corresponding Fe­(III) complexes are typically air-stable and therefore are of great interest .…”

“… 6 Most Fe(II) SCO complexes contain a N 6 surrounding with a moderate ligand field environment 7 while with Fe(III) SCO complexes contain mainly N 4 O 2 , N 2 O 4 , or N 2 O 2 S 2 surroundings with moderate or slightly weaker ligand field environments compared to Fe(II) systems. 8 While many Fe(II) complexes are not air-stable, the corresponding Fe(III) complexes are typically air-stable and therefore are of great interest. 9 Among the many ligand systems that have been employed to study SCO in Fe(III) complexes, SalEen ( Scheme 1 a) stands out.…”