Transient Self-Assembled Materials with Controllable Lifespan for Programmable Fluorescence

Transient structures play a wide range of vital roles in biological systems. Different from static structures that form the skeleton of bio-tissues, transient structures only occur at certain spatial and temporal scales to undertake their duties in the life circle. Despite the significant progress in the field of artificial molecular self-assembly studies, it still remains challenging to construct functional transient structures. Herein, the shaping of transient coordinating self-assembled structures and their fluorescence is reported via host-guest interaction that disfavors the assembly. The host-guest interaction between the luminescent ligand and cyclodextrin drastically changes the kinetics of the coordinating self-assembly, enabling the formation of transient structures. Different from the static equilibrium one with typical monomer emission in the UV region, the transient self-assembly forms excimers, leading to visible emission. More intriguingly, the life cycle of the transient structures can be easily modulated by varying the host-guest ratio, ligand-metal ratio, as well as temperature. This makes it possible to create living patterns that mimic the growth of plants at different life stages. It is therefore envisioned that the creation of transient molecular self-assembly will open a new paradigm in the field of molecular self-assembly featuring advanced materials with dynamic functions. Transient coordinating self-assembly can be achieved by introducing alpha-cyclodextrin (alpha-CD) to compete with Zn2+ for the coordination of 4,4'-biphenyldicarboxylic acid (BPDC). The lifespan of the fluorescent transient self-assembled BPDC-Zn structures can be facilely manipulated by varying the ratio of alpha-CD: BPDC and Zn2+: BPDC, thus leading to programmable fluorescence.image

Automated summary

Transient structures play vital roles in biological systems and can be constructed with functional properties through host-guest interaction. Their lifespan can be easily modulated by various factors, allowing for the creation of living patterns resembling plant growth.