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) 6 ] 4- (HCF); and nitroprusside, [Fe(CN) 5 (NO)] 2- (NP). Two water-insoluble inter-ionic donor-acceptor phases were characterized: the as-prepared microcrystalline reddish-brown (TOXO) 2 [Fe(CN) 6 ]·8H 2 O ( 1a ) with a medium-responsive, hydrochromic character; and the dark violet crystalline (TOXO) 2 [Fe(CN) 6 ]·3.5H 2 O ( 1cr ). Complex 1a , upon external stimulation, transforms to the violet anhydrous phase (TOXO) 2 [Fe(CN) 6 ] ( 1b ), which upon water uptake transforms back to 1a . Using the NP platform resulted in the water-insoluble crystalline salt TOXO[Fe(CN) 5 (NO)]·2H 2 O ( 2 ). The structures of 1cr and 2 , 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.