Preparation And Optical Properties Of Metal Clusters Protected By Dithiolate M-Carborane Ligand

Metal nanoclusters with atom-precise structures have become a new class of nanomaterials due to their diverse structures and rich physical and chemical properties,promising a very broad application prospect in the fields of luminescence,chirality,magnetism,catalysis,electrochemistry,chemical sensing and biomedicine.Due to their strong affinity with metals,thiol ligands have been widely used as protective ligands for metal nanoclusters.Carborane possesses high symmetry,high stability,and three-dimensional aromaticity,and the carboranethiols show a weak reducibility,which make the perfect protective-agents for metal nanoclusters.Therefore,the use of carboranethiol ligands can not only enrich the structure of metal nanoclusters,but also adjust their electronic structure and properties.Based on this consideration,in this thesis we designed and synthesized 1,7-dimercapto-1,7-closo-carborane to construct silver,copper and silver-copper alloy nanoclusters with novel structures and unique luminescent properties.The main work are as follows:1.We synthesized the 1,7-dimercapto-1,7-closo-carborane ligand,and with which a 18e superatomic silver nanocluster[Ag40(C2B10H10S2)12(PPh3)8]2-(1)with near-infrared luminescence properties was obtained.Compound 1 was prepared by a facile one-pot method with silver nitrate,triphenylphosphine and 1,7dimercapto-1,7-closo-carborane in the presence of sodium borohydride.Single crystal X-ray diffraction shows that the molecular structure of compound 1 could be viewed as a Ag12 core protected by a Ag28S24P8 shell.[Ag12(C2B10H10S2)6(PPh3)8](2)was obtained by a similar synthesis but without sodium borohydride.Structure analysis reveals that compound 2 adopts a cage-like structure formed by connecting two Ag6S6P4 units with four carboranylthiol ligands.Interestingly,when the dosage of sodium borohydride was increased to 8 mg,crystals with black complex 1 covered by colorless complex 2 were obtained.Single crystal X-ray analysis only reveals the existence of complex 2,probably due to the low content of the scattered Ag40 nanoclusters.Nevertheless,UV-vis absorption and FT-IR spectra confirmed the co-existence of complexes 1 and 2.This work enriches the research models of silver nanoclusters,and is of great significance to study the relationship between its structure and properties.2.Copper(Ⅰ)cluster[Cu5(C2B10H10S2)6(PPh3)2][Cu(CH3CN)2(PPh3)2](3)and silver(Ⅰ)cluster[Ag5(C2B10H10S2)6(PPh3)2][Ag(PPh3)3](5)were synthesized by a one-pot method using 1,7-dimercapto-1,7-closo-carborane ligand in the presence of sodium borohydride.By doping with Ag atoms,we also successfully obtained a copper-silver alloy cluster[AgxCu5-x(C2B10H10S2)6(PPh3)2][Cu(CH3CN)2(PPh3)2](4).The single crystal X-ray diffraction analysis shows that the three compounds share a similar M5 structure but with different counter cations.We also explored the differences in the optical properties of these compounds,and found that their luminescence properties were completely different at room temperature.Compound 3 only emits orange-red light in solution at room temperature,and is non-emissive in the solid state.Compound 4 shows intense orange-red luminescence in both solid state and solution state,while compound 5 is non-emissive in both solid state and solution state.