Spin States Of 1d Iron(Ii) Coordination Polymers With Redox Active Ttf(Py)(2) As Bridging Ligand

In this manuscript, we report the solvent-dependent synthesis of 1D coordination polymers derived from two planar N2O2-coordinate iron(II) complexes FeL1 and FeL2, which incorporate TTF(py)(2) as a bridging bis-monodentate ligand. The obtained 1D polymers were characterized through elemental analysis, Mossbauer spectroscopy, single crystal structure analysis for 2a center dot 2 DMF, magnetic susceptibility measurements, X-ray powder diffraction, cyclic voltammetry and diffuse reflectance spectroscopy, supplemented by DFT computation. The results revealed additive electronic properties of the sub-units FeL and TTF(py)(2) with only minor mutual influence. Intriguingly however, the solvent-of-synthesis is found to be a steering factor of the magnetic spin crossover properties of the resulting materials, yielding divergent behavior if obtained from DMF, MeCN or EtOH. This becomes strikingly evident for the magnetic properties of the DMF-derived polymer which is found trapped in the low-spin state in the single crystal 2a center dot 2 DMF, but shows a gradual spin crossover if all solvent is removed.