Supramolecular networks derived from hexacyanoferrates and nitrogen heterocyclic cations

Abstract

Eight novel supramolecular framworks (bpyH2)2[Fe(CN)6]•2H2O (1), (bpyH2)(H3O)[Fe(CN)6] (2), (bpeH2)(H3O)[Fe(CN)5(CNH)]•H2O (3), (bpeH2)(H5O2)[Fe(CN)6]•2H2O (4), (dabcoH2)(H3O)[Fe(CN)6]•2H2O (5), (ampyH2)2[Fe(CN)6]•2H2O (6), (tptzH3)2[Fe(CN)4(CNH)2]3•10H2O (7), and (tptzH3)[Fe(CN)6]•3H2O (8) (where bpy =4,4'bipyridine, bpe = 1,2-bis(4-pyridyl)ethylene, dabco = 1,4-diazabicyclo[2.2.2]octane, ampy = 4-aminomethylpyridine, tptz = tris(4-pyridyl)triazine) have been synthesized by the reaction of the nitrogen heterocycle with ferrocyanide or ferricyanide salts, under mild conditions. The supramolecular structures are constructed mainly by cooperative hydrogen bonding between the inorganic anions, the organic cations and oxoniums or lattice water molecules. There are some characteristic features that can separate the compounds in groups. Those are a) increase of H-bonding ability by formation of supramolecular complexes, b) formation of hydro-and dihydro-hexacyanoferrates and c) the participation of the cationic heterocycle as constituent of the structure or as a guest. The structures are additionally discussed in terms of topology.

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

“…These changes could be easily observed by the naked eye. Trying to obtain SCXRD-quality crystals, we used stable hexacyanoferric(II) acid (H 4 [Fe(CN) 6 ]) as a source of HCF since numerous crystalline structures of organic hexacyanoferrates, including the pyridinium-type cations, have been prepared and described [20][21][22][23][24]. Many such complexes contain protonated cyanoferrate(II) platforms, and therefore, regardless of the charge of the organic cation, they have different molecular formulas, determined by the different charge of the cyanoferrate(II).…”

Cubic Three-Dimensional Networks of the Cyanometalate [Fe(CN)6]3– with the Ditopic Halogen Bond Donor Diiodoacetylene C2I2

“…Because of their higher nucleophilicity in comparison with purely organic molecules, inorganic coordination compounds are increasingly used as halogen bond acceptors. − Particularly useful are cyanometalates [M­(CN) x ] z − due to their highly variable topologies and their strongly coordinating properties . While a few examples of cyanometalates as halogen bond acceptors have been reported, − their ability to form strong hydrogen bonds (and also network structures) has to be taken into account. − Consequently, the crystal engineering of networks involving both hydrogen and halogen bonding is especially challenging . Furthermore, their tendency for significant deviations from linear halogen bonds (CN···I ≠ 180°) reduces the structural predictability of such interactions .…”