Polymorph control of anhydrous guanine

Prof. Dr. Yurong Ma

School of Chemistry and Chemical Engineering
Beijing Institute of Technology, Beijing, China

07.02.2019 13:30 ML 630

Amorphous guanine was proposed to be the mineralization precursor of biological anhydrous guanine β phase in vesica of the Koi fish scales1. Guanine is the most widespread organic crystal existing in organisms to produce structural colors. Guanine monohydrate and two anhydrous guanine phases (AG), and , are three well known crystalline phases of guanine. The excellent optical performances of guanine crystals are mainly attributed to the crystalline AG β micro-platelets exposed (100) plane and high refractive index (1.83) 2. Herein, single crystalline AG β phase nanoplatelets were synthesized via transformation from amorphous guanine phase in the laboratory by using macromolecules as additives. AG in pure phase can also be obtained by changing the reaction conditions. A novel crystal phase of anhydrous guanine consisting of N9-G purine ring was obtained by dehydration of guanine monohydrate (GM) at 111 °C, termed as dehydrated-GM, which is the first reported tautomeric polymorph of AG (N7-G purine ring). The Dehydrated-GM has very good water harvest ability (8 wt%) with a fast rate ( in 30 min) even at relatively low room humidity (below 20 %) and low temperature (40 °C). We realized the synthesis of three polymorphs of anhydrous guanine AG AG  and dehydrated-GM in this work.