Deciphering Spin-State Equilibrium in [Fe2L3] Helicates: A Comparative Study in Solid and Solution State

A series of metallosupramolecular ferrous [Fe2L3] helicates have been synthesized from in-situ prepared flexible bis-bidentate imidazolyl ligand and characterized using single crystal XRD using synchrotron radiation. With variation in the temperature, both the complexes M1 and M2 exhibit Spin-State Switching, which is confirmed from magnetic susceptibility measurements in the solid state and from variable temperature Evans 1H-NMR in the solution state. Further investigations have been conducted to get insights into the spin state equilibri-um from the variable temperature NMR method. Additionally, the switching process is very much dependent on the short interactions within the system, hence sensitive to solvent loss at higher temperatures