Synthesis and Properties of a Thermochromic Spin Crossover Fe^II Complex: An Undergraduate Coordination Chemistry Laboratory Experiment

Anne Vallée (1) , Cyrille Train (2, 3) , Cécile Roux (1)

1 LCMCP - Laboratoire de Chimie de la Matière Condensée de Paris
2 LNCMI-G - Laboratoire national des champs magnétiques intenses - Grenoble
3 IUF - Institut universitaire de France

In this third-year undergraduate experiment, a coordination complex [Fe(NH2trz)3]Br2·H2O (NH2trz is 4-amino-1,2,4-triazole, C2H4N4) was synthesized and characterized by IR and UV–visible spectroscopies. This compound exhibits a spectacular reversible purple-white thermochromic transition upon heating–cooling with a large hysteresis centered at room temperature. The thermochromic transition is related to the spin crossover (SCO) from the low-spin state (LS, purple, S = 0, diamagnetic) to the high-spin state (HS, white, S = 2, paramagnetic). During this experiment, students discovered synthetic methods, such as anion metathesis and Ostwald ripening, and physical properties, such as magnetic properties, thermochromism, and bistability phenomenon, altogether leading to possible applications in optical-data storage and display.

Mots clés: Upper-Division Undergraduate; Inorganic Chemistry; Laboratory Instructions; Hands-On Learning/Manipulative; Coordination Compounds; Crystal Field/Ligand Field Theory; IR Spectroscopy; UV-Vis Spectroscopy

Domaines: Chimie

Anne Vallée, Cyrille Train, Cécile Roux. Synthesis and Properties of a Thermochromic Spin Crossover Fe^II Complex: An Undergraduate Coordination Chemistry Laboratory Experiment. Journal of Chemical Education, 2013, 90 (8), pp.1071-1076. ⟨10.1021/ed4000487⟩. ⟨hal-01137447⟩