Effect of the chemical structure of an equatorial ligand on the spin crossover properties of the Fe(III) complex with 4-styrylpyridine axial ligands

Abstract

In order to study the effect of the chemical structure of the equatorial ligand on the spin state of the Fe(iii) ion in complexes with invariable photoisomerizable 4-styrylpyridine axial ligands and different tetradentate Schiff bases, several new Fe(iii) complexes have been first synthesized, characterized, and studied by UV-vis, NMR, and EPR spectroscopies. The general chemical formula of the complexes is [Fe(SB)Sp2]BPh4·MeOH, where Sp is trans-4-styrylpyridine and SB are dianions of Schiff bases: salen, bzacen, and acen [salen = N,N′-ethylenebis(salicylaldimine) 1, acen = N,N′-ethylenebis(acetylacetonylideneimine) 2, and H2bzacen = N,N′-ethylenebis(benzoylacetonylideneimine) 3]. The results of the EPR and NMR measurements of the complexes both in the solid state and in solutions showed that the more methyl groups and less aromatic rings in the equatorial ligand, the more abrupt spin-crossover was observed in the complex. The dependence of the magnetic properties of the complexes on the state of matter and the presence of a solvent (powder, liquid solutions, and vitrified solutions) are noted.

Structural, Magnetic, and Electrochemical Characterization of Iron(III) and Cobalt Complexes with Penta‐N3O2‐dentate Ligands

“…[12][13][14][15] Complexes with Schiff base ligands have the advantages of mostly simple syntheses and chemical modifications are easily possible. [16][17][18][19][20] One example is the series of [M III (L R1,R2 )X] complexes (M: Co or Fe; L: N,N'-bis(2'-hydroxybenzylidene)-1,6diamino-3-azahexane; X: pseudo halide or organic molecule) which was studied extensively in the past (Figure 1). [21][22][23][24][25][26][27] The Co(III) complexes are in low spin (LS) states, [27] whereas some Fe(III) complexes showed temperature induced reversible conversions between LS and high spin (HS) states, called spin crossover (SCO).…”

A rare octacoordinated mononuclear iron(III) spin-crossover compound: synthesis, crystal structure and magnetic properties

“…In comparison to other types of possible molecular switches (Boonprab et al, 2019;Hayami et al, 2001), SCO transition-metal complexes based on Fe II can easily switch between high-spin (HS, S = 2) and low-spin (LS, S = 0) states under external perturbation, such as temperature, physical and chemical pressure, or magnetic or electrical switching (Trzop et al, 2016;Zhang et al, 2017Zhang et al, , 2018Lan et al, 2019;Jin et al, 2019;Ide et al, 2017;Hayami et al, 2001;Pavlik et al, 2020;Kahn & Martinez, 1998;Murphy et al, 2017), and thus show great potential applications in memory devices, sensors, etc. (Turanova et al, 2020;Kahn & Martinez, 1998).…”

Selective functionalization of C(sp3)–H bonds: catalytic chlorination and bromination by IronIII-acacen-halide under ambient condition

“…S3 and S4, ESI†). The UV-vis absorption spectra in acetonitrile indicate that 1 III -Cl and 1 III -Br possess ligand-to-metal charge transfer (LMCT) 10 bands centered at 498 nm ( ε = 2899 M −1 cm −1 ) and 518 nm ( ε = 3023 M −1 cm −1 ), respectively (Fig. S5, ESI†).…”