engleski

Solid-State Chemistry and Polymorphism of the Nucleobase Adenine

The nucleobase adenine plays a pivotal role in the chemistry of life but is also becoming increasingly interesting as a building block in the synthesis of functional solid materials. Although commercially available as a solid, adenine’s solid-state chemistry has so far been neglected. In this comprehensive study it is shown that adenine is most often marketed as a mixture of two polymorphs, one previously known and a new polymorph. Both polymorphs exhibit layered structures with different hydrogen-bonding patterns within layers. The crystal structure of the new polymorph was elucidated using synchrotron powder X- ray diffraction. Polymorph occurrence conditions, interconversion, and the difference in their thermodynamic stability were established theoretically and experimentally revealing the polymorph with Z' = 2 (known) as stable relative to the polymorph with Z' = 1 (new). The adenine layers in both polymorphs are connected by weak interactions likely resulting in stacking faults which are manifested in anisotropic line broadening of their powder diffraction patterns. Analysis of a few commercial samples of adenine revealed them all to be a polymorph mixture, which could be inconvenient in experiments where properties of the solid material could be relevant.

adenine ; polymorphism ; solid-state ; powder diffraction ; thermodynamics

nije evidentirano