Supramolecular networks derived from hexacyanoferrates and nitrogen heterocyclic cations

Abstract

Eight novel supramolecular frameworks (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.