Abstract
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.