Supramolecular Solid Complexes between Bis-pyridinium-4-oxime and Distinctive Cyanoiron Platforms

The structural features and optical properties of supramolecular cyanoiron salts containing bis-pyridinium-4-oxime Toxogonin (TOXO) as an electron acceptor are presented. The properties of the new TOXO-based cyanoiron materials were probed by employing two cyanoiron platforms: hexacyanoferrate(II), [Fe(CN) ] (HCF); and nitroprusside, [Fe(CN) (NO)] (NP). Two water-insoluble inter-ionic donor-acceptor phases were characterized: the as-prepared microcrystalline reddish-brown (TOXO) [Fe(CN) ]·8H O ( ) with a medium-responsive, hydrochromic character; and the dark violet crystalline (TOXO) [Fe(CN) ]·3.5H O ( ). Complex , upon external stimulation, transforms to the violet anhydrous phase (TOXO) [Fe(CN) ] ( ), which upon water uptake transforms back to . Using the NP platform resulted in the water-insoluble crystalline salt TOXO[Fe(CN) (NO)]·2H O ( ). The structures of and , solved by single-crystal X-ray diffraction, along with a comparative spectroscopic (UV-vis-NIR diffuse reflectance, IR, solid-state MAS-NMR, Mössbauer), thermal, powder X-ray diffraction, and microscopic analysis (SEM, TEM) of the isolated materials, provided insight for the supramolecular binding, electron-accepting, and H-bonding capabilities of TOXO in the self-assembly of these functionalized materials.