High-spin bis[(S or R)-N-1-(Ar)ethyl-salicylaldiminato-κ2N,O]-Λ/Δ-iron(II): Combined studies of syntheses, spectroscopy, diastereoselection, electrochemistry, paramagnetic, thermal, PXRD and DFT/TDDFT

Abstract The enantiopure Schiff bases (S or R)-N-1-(Ar)ethyl-salicylaldimine (S or R-HL) react with the iron(II) chloride to give high-spin bis[(S or R)-N-1-(Ar)ethyl-salicylaldiminato-κ2N,O]-Λ/Δ-iron(II) {Ar = C6H5 (FeSL1 or FeRL1), p-OMeC6H4 (FeSL2 or FeRL2) and p-BrC6H4 (FeSL3 or FeRL3)}. ECD spectra show expected mirror-image relationship for the enantiomeric pairs and confirm the enantiopurity of the complexes in methanol. The electronic spectra calculated by DFT/TDDFT fit well to the experimental spectra. Comparisons of experimental ECD spectra for FeRL2 (or FeSL2) with those of the calculated spectra for Λ-FeRL2/Δ-FeRL2 (or Δ-FeSL2/Λ-FeSL2) exhibit diastereoselection and induced chirality (Λ vs. Δ) at-metal centre by R- or S-ligand and prefer formation of Δ-FeRL2 (or Λ-FeSL2) in solution. CV results demonstrate three redox peaks associated to the FeI/0, FeII/I and FeIII/II couples, respectively in acetonitrile. Thermal analyses by DSC suggest an irreversible phase transformation from solid to isotropic-liquid phase. VT magnetic measurements show relatively high magnetic moment values (i.e., μeff. = 4.6–5.0 μB), correspond to the tetrahedral high-spin iron(II)-Schiff base complexes in methanol. Fair matching between experimental and simulated PXRD patterns indicates the ligands and complexes having well define crystalline nature with various degrees of crystallinity.