Ligand field tuned spin crossover for an iron(II)-di(diamine) system

• Two new complexes from 4,5-dimethy-2-(pyridine-2-yl)imidazole and NCX have been presented.
• Influences of NCX on spin-crossover have been investigated.
• The vibrational and absorption spectra of these two complexes have been quantificationally visualized.

Investigation of spin-crossover in iron(II)-di(diamine) system, based on ligands L1, 4,5-dimethy-2-(pyridine-2-yl)imidazole, has been presented in this paper. The methyl group at the adjacent sites of the donor atoms in ligand L1 can generate the crossover situation for the iron(II) tris(diimine) system. While for the iron(II)-di(diamine) system with L1, the results are complicated: complex 1 {Fe(L1)2(SCN)2} displays paramagnetic behavior while 2 {Fe(L1)2(SeCN)2} is in crossover situation. The difference was attributed to the various ligand field strength of SCN− and SeCN−, which also resulted to the blue-shift of IR and Raman spectra, as well as red-shift and decrease in molar absorptivity of UV–Vis absorption spectrum.

Investigation of spin-crossover in iron(II)-di(diamine) system, based on ligands L1, 4,5-dimethy-2-(pyridine-2-yl)imidazole, has been presented. The methyl group at the adjacent sites of the donor atoms in ligand L1 can generate the crossover situation for the iron(II) di(diimine) system. For complex 1 {Fe(L1)2(SCN)2}, it displays paramagnetic behavior, while for 2 {Fe(L1)2(SeCN)2}, it is in complete crossover situation. The difference was attributed to the various ligand field strength of SCN− and SeCN−.Figure optionsDownload as PowerPoint slide