• Spin crossover;
  • Iron;
  • N,O li­gands;
  • Ligand effects;
  • Magnetic properties


Two mononuclear spin-crossover compounds Fe(L1)2 (1) and Fe(L2)2 (2) {HL1 = 2-hydroxy-3-methyl-N′-[1-(pyridine-2-yl)butylidene]benzohydrazide, HL2 = 2-hydroxy-N′-[1-(pyridine-2-yl)butylidene]benzohydrazide} were successfully synthesized. The magnetic measurements of the compounds revealed different thermal magnetic behavior. Compound 1 undergoes a gradual complete thermal spin crossover (SCO) with T1/2[UPWARDS ARROW]/[DOWNWARDS ARROW] = 243/240 K and a hysteresis loop of 3 K. Compound 2 shows a gradual incomplete SCO during the measurable temperature region with T1/2 ≈ 330 K. Through the comparison of the magnetic and structural results for 1 and 2 with previously reported related compounds, the alkyl substitutions of the ligand were considered to affect the ligand-field strength and hydrogen-bonding interactions. In addition, photomagnetism results showed an 87 % photoconversion and 36 K of T(LIESST) (LIESST = light-induced excited spin-state trapping) for compound 1. The results enrich the knowledge on how to control the spin-crossover behavior in the new system.