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Solid-state chemistry and polymorphism of the nucleobase adenine

The nucleobase adenine plays a vital role in the chemistry of life and is becoming increasingly interesting as a building block in the synthesis of functional solid materials. In this comprehensive study, it is shown that adenine is often found as a mixture of two 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 as well as experimentally. Studies revealed that polymorph with Z' = 2 (known) is 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.

solid-state, polymorphism, adenine

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