A 2D Layered Spin Crossover Complex Constructed by NH···Cl^- Hydrogen Bonds: [Fe^IIH₃L^Me]Cl·I₃ (H₃L^Me = Tris[2-(((2-methylimidazoyl-4-yl)methylidene)amino)ethyl]amine

A 2D layered spin crossover complex, [FeIIH3LMe]Cl·I3, has been synthesized from the reaction of FeIIICl3, a tripod ligand (H3LMe = tris[2-(((2-methylimidazoyl-4-yl)methylidene)amino)ethyl]amine), and NaI in methanol. The compound showed an abrupt spin transition between the HS (S = 2) and LS (S = 0) states at T1/2 = 110 K without hysteresis. The crystal structures of the HS and LS states were determined at 180 and 90 K. A 2D layered structure is composed of NH···Cl- hydrogen bonds between the Cl- ion and three neighboring imidazole groups of [FeIIH3LMe]2+. The green light irradiation at 5 K induced the LIESST effect, and the thermal relaxation process from the HS to LS state showed a sigmoid curve at T > 55 K.