Hexakis (Propargyl-1H-tetrazole) iron(II) X2 [X = BF4, ClO4]—spin switchable complexes with functionalization potential and the myth of the explosive SCO compound

Abstract

Spin crossover complexes with ligands suitable for further functionalization could allow for an easy access to multifunctional switchable materials. Within this context, we recently characterized the Fe(II) SCO complexes of propargyl-1H-tetrazole. Although the design of the ligand seems similar to the one of the well-known propyl-1H-tetrazole, the spin transition behavior is notably different. Both compounds reported herein feature a gradual spin transition with a T1/2 shifted to lower temperatures, compared to the more flexible propyl-ligand. Due to the potential instable structure of these compounds, especially of the perchlorate complex, we also investigated our compounds with regard to their sensitivity against thermal and mechanical stress. These experiments led to the conclusion that the proper handling includes no enhanced risk of explosive decomposition.