Synthesis,Structures And Properties Of Carborane Dithiolate-protected Coinage-metal Clusters-based Materials

Atomically precise coinage-metal nanoclusters（NCs）have received significant interest during the last decade owing to their numerous properties and potential applications in catalysis,imaging,sensing,medicine,and optoelectronics.However,drawbacks like the uncontrollable synthetic process,instability and low room-temperature quantum yields hampered the in-depth study on atomically precise coinage-metal clusters.It remains a great challenge to realize the controlled synthesis and functionalization.Icosahedral carborane with unique electronic structures is usually able to regulate the photophysical properties of their bonded luminescent groups.The large size and spherical geometry make it difficult to cover the core completely in the metal cluster ligand shell,which facilitates the coordination of small solvent molecules.The monodendate pyridine ligands were used to replace these CH₃CN species site-specifically,giving stable solid-state superatomic-nanocluster materials with its core structure intact.Using bidentate N-containing ligands to bridge the superatomic Ag₁₄ building blocks,we constructed an unprecedented hierarchical series of1D-to-3D superatomic silver cluster assembled-materials.A Cu₁₄ nanocluster with partial Cu（0）character was synthesized via self-reduction reaction by employing o-carboranedithiolate ligand.A pair of cluster analogues have been synthesized by bottom-up assembly and complete-metal-exchange-induced the cluster-to-cluster conversion.It provides a model platform for further study differences of the property between copper and silver clusters.This paper includes three parts as follows:1.Based on our previous work,using bidentate N-containing ligands to bridge the superatomic Ag₁₄ building blocks,we constructed an unprecedented hierarchical seriesof1D-to-3Dsuperatomicsilvercluster-assembled-materials{[Ag₁₄（Pyrazine）_6.5（DMAc）（CH₃CN）_0.5]·2DMAc}_n（SCAM-1,1D）,{[Ag₁₄（dpd）₂（CH₃CN）₄]·DMAc}_n（SCAM-2,2D）,{[Ag₁₄（bpy）₄]}_n（SCAM-3,3D）and{[Ag₁₄（dpbz）₄]}_n（SCAM-4,3D）.SCAM-4 is air-stable up to 220 ^oC and exhibits tunable dual emission with wide-range thermochromism.The present study constitutes a major step towards the development of ligand-modulation of the structure,stability,assembly and functionality of superatomic silver nanoclusters.2.o-carboranedithiolate was employed in the ligand shell to protect an atom-precise Cu⁰-containing fcc-Cu₁₄ cluster.The one-pot synthesis involved synchronous Cu²⁺to Cu⁰ by self-reduction of the dithiol ligand and the formation of the copper cluster Cu14-8CH3CN,which has a virtually identical silver structural analog,i.e.,Ag₁₄(C₂B₁₀H₁₀S₂)₆（CH₃CN）₈（hereafter as Ag14-8CH3CN）.Nevertheless,density functional theory（DFT）calculations revealed that the electronic structure of Cu14-8CH3CN differs significantly from the superatom electronic configuration of Ag14-8CH3CN.Moreover,Cu14-8CH3CN shows room-temperature luminescence and good electrocatalytic activities in ethanol oxidation reaction and detection of H₂O₂.This work provides a perspective for preparing Cu⁰-containing clusters via a self-reduction procedure.This pair of unprecedented analogous molecular nanoscale systems offer an ideal platform to investigate the fundamental differences between copper and silver in terms of catalytic activity and optical properties.3.A pair of atom-precise copper/silver-thiolate halide cluster analogues,namely[Cu₁₇/Ag₁₇I₃S(C₂B₁₀H₁₀S₂)₆（CH₃CN）₁₁],（Cu17 and Ag17）,obtained by bottom-up assembly and complete-metal-exchange-induced cluster-to-cluster transformation,respectively.With the radius of the metal atom increased,the optical absorption of nanoclusters was obviously red-shifted,and yet solid-state luminescence was greatly blue-shifted.SCXRD analysis,control experiments and DFT calculations revealed the phenomenon resulted from the inherently distinguishing properties of Cu and Ag,and different Cu???Cu and Ag???Ag interactions.This work constitutes a major step toward the development of cluster-to-cluster conversions and controllable cluster’s properties by metal component.In summary,the site-specific tailoring and assembly strategy with organic ligands not only greatly improved the stability but also regulated the emission properties of the target materials.The modification and assembly strategies of surface ligands of superatoms provided a direct way to understand the surface functionalization-property relationship and produce new functional materials.The rarely reported structural isomers and pseudoisomers of metal clusters that mainly differ in the arrangement of metal atoms and identical analogues that have partially or completely different metal components provide excellent platforms for precise investigation of the subtle structure-property relationships of metal clusters.Extensive work including site-specifically surface modification and assembly of Group 11 and other noble-metal nanoclusters with various functionalized ligands are underway in our lab.