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A new self-assembling system prepared from guanosine and 2-formylbenzeneboronic acid showed a high selectivity to potassium ions and has a fluorescent enhancement effect on berberine, which can be used for serum potassium detection.

Elastic organic single crystals with light-emitting and multi-faceted bending properties are extremely rare. They have potential application in optical materials and have attracted the extensive attention of researchers. In this paper, we reported a structurally simple barbituric derivative DBDT, which was easily crystallized and gained long needle-like crystals (centimeter-scale) in DCM/CH 3 OH (v/v = 2/8). Upon applying or removing the mechanical force, both the ( 100) and ( 040) faces of the needle-like crystal showed reversible bending behaviour, showing the nature of multi-faceted bending. The average hardness (H) and elastic modulus (E) were 0.28 � 0.01 GPa and 4.56 � 0.03 GPa for the (040) plane, respectively. Through the analysis of the single crystal data, it could be seen that the van der waals (CÀ H•••π and CÀ H•••C), Hbond (CÀ H•••O) and π•••π interactions between molecules were responsible for the generation of the crystal elasticity.Interestingly, elastic crystals exhibited optical waveguide characteristics in straight or bent state. The optical loss coefficients measured at 627 nm were 0.7 dBmm À 1 (straight state) and 0.9 dBmm À 1 (bent state), while the optical loss coefficient (α) were 1.5 dBmm À 1 (straight state) and 1.8 dBmm À 1 (bent state) at 567 nm. Notably, the elastic organic molecular crystal based on barbituric derivative could be used as the candidate for flexible optical devices.

A self-assembled G-quadruplex formed by guanosine and borate as the chiral scaffold was used to catalyze the asymmetric Friedel–Crafts reaction in water. Catalysis, depending on the self-assembly of guanosine and borate into a fibrillar structure in the presence of Cu2+ ions, can be modulated by the assembly concentration, temperature, and amount of Cu2+ ions. Detailed spectral experiments proved that the guanosine-based assembly in solution was responsible for the enantioselective catalysis, rather than small-molecule species. Some of the similar G-quartet assemblies were unable to promote the asymmetric reaction, implying unique properties of the current system, including excellent lifetime stability and supramolecular chiral structures. This work provided the first example of the self-assembled G-quadruplex achieving enantioselective catalysis and some perspective to better understand the design of nucleoside-based self-assemblies for an enantioselective reaction. In view of guanosine as a building block, these findings may be applied to discuss the prebiotic chiral catalyst preceded ribozymes.

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