Proton-driven coordination-induced spin state switch (PD-CISSS) of iron(II) complexes

Here we report the completely reversible spin state switch of the naturally diamagnetic tris(bipyridine) iron(II) complex and the spin crossover complex bis(2,6-bis(1H-pyrazol-3-yl) pyridine) iron(II) by the variation of the pH followed by H-1-NMR, UV-Vis spectroscopy, and magnetic and relaxivity measurements in solution and as composite materials encapsulated in a zeolite matrix.