Diastereomeric Ratio Affecting the Spin Transition Behavior of Three Fe₄L₆ Tetrahedral Cages in Solid and Solution Phases

Spin crossover (SCO) in metal‐organic cages (MOCs) remains underexplored despite their potential for fascinating applications in molecular switches and sensors. The interplay between the structural flexibility of MOCs and spin state switching offers a promising avenue for tuning magnetic properties in a controlled environment. Herein, it is reported on how varying diastereomeric ratios, influenced by magnetically inequivalent protons, alter ligand field strength and result in distinct SCO profiles. Three Fe II 4 L 6 tetrahedral MOCs are synthesized via subcomponent self‐assembly of benzidine, pyridine‐2‐carboxaldehyde, and FeX 2 salt (MOCs 1 – 3 ) having anions tetrafluoroborate, perchlorate, and triflimide, respectively. Different binding motifs of the syn and anti ‐conformations of the diimine ligands coupled with the anion templation render a combination of different diastereomers of the MOCs, altering the structural and magnetic properties of the resulting assemblies. MOCs 1 and 2 exhibit identical and gradual SCO behavior, whereas MOC 3 exhibit SCO above room temperature in the solid state. Variable temperature 1 H NMR and UV‐Visible spectroscopy predict the spin transition temperature to be in the order: T ½ ( 1 ) < T ½ ( 2 ) < T ½ ( 3 ), emphasizing the role of ligand conformation and anion templation on SCO behavior.