Tuning The Structure Of Inorganic Coordination Networks In Au(?)-Thiolate 2D Self-assemblies With Organic Ligands

Two-dimensional(2D)materials have shown great electronic,magnetic,photonic,catalytic performances due to their 2D quantum confinement and large specific surface area.2D self-assembled materials via non-covalent interactions have great advantages in flexibility,stimuli-responsiveness and environment acclimation.Compared with the covalent 2D materials,the research on 2D self-assembled materials is still at start.On the preparation of 2D self-assembled materials,they are mainly fabricated with the assistance of template and interface to help the 2D assembly.The template-free self-assembly is very challenging.On the development of the properties and functions of 2D self-assembled materials,their assembled structures,geometrical morphologies,photoelectric properties and stabilities have well tunability due to the non-covalent interactions.But it is still a challenge to tune the structures and properties of the 2D self-assemblies from molecular/atomic level,because when the intermolecular/interatomic interactions are the main driving forces for self-assembly,the stability of the self-assemblies can be affected by the changing of the strength of these weak interactions.Au(I)-thiolate coordination polymers can act as an excellent building block to prepare.They can assemble into 2D materials through the hierarchical assembly process.Similar with bio-macromolecules,there are multi-type weak interactions and these weak interactions can adjust their strength to adapt the change of others without resulting in the damage of Au(I)-S coordination networks.So we choose Au(I)-thiolate 2D assemblies as a model to tune their structures and properties from atomic level by adjusting their weak interactions.Firstly,due to the environment-sensitive of non-covalent interactions,we tune the structure of 2D Au(I)-MPA lamellar assemblies by changing the solvent environment.We prepare two pseudopolymorphs of Au(I)-MPA 2D assemblies in two solvents of water and ethylene glycol(EG)and resolve their unit cell parameters.The two assemblies have distinct optical property,morphology and thermal stability.The solvent-depended pseudopolymorphism is caused by their different ratio of counter ions of H~+and Na~+and the internal structural parameters.The two assemblies cannot inter-convert to each other before decomposition temperature,demonstrating high structural preservation owning to the collective interactions inside the structures.This work provides a proper model to understand how environments decide the acclimated structure.The solvent-depended pseudopolymorphism of 2D Au(I)-MPA assemblies indicates that the external organic ligands can adjust the internal Au(I)-S inorganic coordination networks of the assemblies.But there are only two stable pseudopolymorphs and it cannot tune the Au(I)-S inorganic coordination networks continuously.Due to the high defect-tolerance of two-dimensional materials,we provide a double-ligands co-assembly method to continuously tune the Au(I)-S inorganic coordination networks.A series of thiol ligands with similar sizes to MPA co-assemble with MPA to prepare the homogeneous Au(I)-nMPA-co-SR 2D co-assemblies.The geometrical morphology,the orbital levels and the bandgap of the Au(I)–S inorganic network,the chemical reactivity of the co-assemblies can also be adjusted through the content of co-ligand.This is the first work to give the detailed energy diagrams through the experimental data and demonstrates the first example of continuously tuning the electron band structure of a new type of inorganic–organic composite semiconductors by low-temperature water-phase co-assembly.This cannot be achieved from either inorganic or organic semiconductors.Then,inspired by the natural twisted 2D?-sheet structure,we use large sized GSH to co-assemble with MPA to create a rugged surface and prepare the 2D Au(I)-MPA-co-GSH single-layer self-assemblies with uniform size distribution and regular oblique triangular shape.The packing model of Au(I)-MPA-co-GSH single-layer assemblies is deduced from their high-resolution AFM and electron diffraction.By monitoring the assembly process,the large sized doping ligand of GSH not only mediates the dynamic assembly process through the ligands-exchange,but also prevents the regular inter-layer stacking interactions.Besides,the Au(I)-MPA-co-GSH single-layer assemblies have well colloidal and thermal stability,a wide range of pH stability,low cell toxicity and unique 2D planar chirality.The unique 2D planar chirality is resulted from the preferential conformations of closely packing ligands fixed by the Au(I)-S inorganic coordination networks and the changing of the Au(I)-S inorganic coordination networks can also result in the changing of the CD signals.In conclusion,because the weak interactions in free-standing Au(I)-thiolate 2D assemblies are cooperative and restricted each other,the Au(I)-S inorganic coordination networks of free-standing Au(I)-thiolate 2D assemblies are tuned by adjusting the interactions of organic ligands through solvent-environment and co-assembly.This work provide a new method to prepare and tune the free-standing2D assemblies.Au(I)-thiolate coordination polymers have a broad range of applications in anti-rheumatism drugs,nanoparticle synthesis,luminophor and sensing,the pseudopolymorph study will also open a new way on their structural modulation.Besides,from our work,we can deeply understand how weak interactions effect each other to realize the structural stability and stimuli-responsive in life system.