A new guaninate hydrate K+ · C5H4N5O − · H2O: crystal structure from 100 to 300   K in a comparison with 2Na+ · C5H3N5O2 − · 7H2O

A new guanine salt hydrate, K+ · C5H4N5O − · H2O, was obtained and characterized by single-crystal X-ray diffraction in the temperature range 100   K – 300   K and compared with that of the previously documented sodium salt hydrate (2Na+ · C5H3N5O2 − · 7H2O) [Gur& Shimon (2015). Acta Cryst. E71, 281 – 283; Gaydamaka et al. (2019). CrystEngComm, 21, 4484 – 4492]. Both sodium and potassium salt hydrates have channels. However, the structure of the channels, the cation coordination, the protonation (and, respectively, the charge) of the guanine anions, as well as the role of water molecules in the crystal structure are different for the two salt hydrates. In the crystal structures of the potassium salt, the guanine anions are linked via hydrogen bonds into quartets that form open cylindrical channels in a honeycomb framework. Water molecules `line the walls' of the channels, whereas the potassium cations fill the intra-channel space. This contrasts with the structure of the sodium salt hydrate in which guanine anions form channels with water molecules filling in the channel space together with sodium cations coordinating them. The 1D anionic assembly generated through numerous hydrogen bonds and cation interactions with guanine anions and water molecules is energetically the most distinctive part of the structure of the potassium salt hydrate. In the case of the guanine sodium salt, the structure contains purely inorganic polymeric fragments – sodium cations ...
Source: Acta Crystallographica Section B - Category: Chemistry Authors: Tags: guanine single-crystal X-ray diffraction nucleobase tautomers anisotropy of thermal expansion structure – properties relations crystal salt hydrates role of water in forming a crystal structure channel structures intermolecular int Source Type: research