Fluoroaluminates of purine and DNA bases, adenine, guanine: [Hpur]2·(AlF5), [Hade]3·(AlF6)·6.5H2O, [Hguan]3·(Al3F12)

New purinium, adeninium and guaninium fluoroaluminates, [Hpur]2·(AlF5), [Hade]3·(AlF6)·6.5H2O and [Hguan]3·(Al3F12), are synthesized by microwave heating assisted hydrothermal synthesis at 120 °C or 190 °C. The crystallisation is difficult; all crystals of [Hpur]2·(AlF5) and [Hade]3·(AlF6)·6.5H2O are very small while only a microcrystalline powder of [Hguan]3·(Al3F12) is obtained. The structures are determined from crystal ([Hpur]2·(AlF5) and [Hade]3·(AlF6)·6.5H2O) or powder ([Hguan]3·(Al3F12)) X-ray diffraction data. In [Hpur]2·(AlF5), trans-chains of corner sharing octahedra lie along the c axis of the tetragonal cell (a = 18.997(2) Å, c = 3.6980(4) Å, P4/n, Z = 4). In [Hade]3·(AlF6)·6.5H2O, the octahedral AlF6 units lie in (010) planes with water molecules. In [Hguan]3·(Al3F12), trimers of corner sharing octahedra are associated by opposite vertices along the c axis of the trigonal cell (a = 14.254(1) Å, c = 3.629(1) Å, P3, Z = 1). The purine, adenine and guanine amines are monoprotonated and lie between the preceding chains or layers. Hydrogen bonds between fluoride ions and amine groups of organic cations or, eventually, water molecules ensure the stability of the structures, together with N–H⋯O intermolecular bonds between guaninium cations in [Hguan]3·(Al3F12). The N(7)H-amino and N(9)H-amino tautomeric forms of [Hade]+ are simultaneously found in [Hade]3·(AlF6)·6.5H2O.

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