Synthesis, Structures, Photophysical Properities Of Silver Chalcogenide Nanoclusters Based On Naphthalen-2-yl-methanethiol Ligand

Metal clusters are becoming important materials of current research in different fields of nanoscience. Their tiny size, consisting of tens to hundreds of atoms, brings new fascinating properties due to the quantum confinement effect. Hence, they display new optical, electrical and chemical properties leading to particularly attractive applications in biological labeling, optical sensing, catalysis and electrocatalysis. Wherein, Au/Ag nanoclusters have been proved to be excellent flurophores for chemical sensing and bioimaging. Usually, these Au/Ag nanoclusters need to be protected with templates or capping agents such as aryl, aliphatic, and thiols to prevent their aggregating. Thiolate capped/stabilized Au or Ag clusters have been a focus of intensive research owing to the strong interaction between thiols and Au or Ag. So far, a series of metal-rich silver chalcogenide clusters with well-defined structures have been obtained. Building silver chalcogenide nanoclusters with appealing structures and unique properties by selecting suitable ligands is the main part of our research.In this article, our work includes three parts as follows:1、We devised a new thiolate ligand naphthalen-2-yl-methanethiol, by which we synthesized Ag12(SCH2C10H7)6(CF3CO2)6(CH3CN)6(1) cluster with diameters in the nanometer range. Its structure and properties have been characterized.The luminescent and thermochromic properties of the nanocluster 1 have been investigated in detail. More interesting is that this nanocluster with single-crystal structure exhibits dual emission, originating from the excimer-like luminescence component, in which an electronically excited state of an aromatic fluorophore is stabilized by interaction with a second aromatic unit in an ‘excited state complex’, and the central Ag-S cluster respectively. The dual emission behavior shows different variation tendency with temperature. When cooling from 298 to 77 K under 370 nm excitation, the HE emission bands of the nanocluster were still kept at 570 nm with the stepwise increase of intensity. Meanwhile the LE emission bands were gradually red shifted from 660 nm to longer wavelength and reached 690 nm at 77 K, accompanying the decrease first and then increase in intensity, resulting in thermochromism spanning from red to brighter yellow. To the best of our knowledge, this is the first report to address the thiloate ligand adjusting emission of silver thiolate nanocluster.2 、 We report the syntheses and crystal structures of Ag14(SCH2C10H7)6(CF3CO2)8(DMAc)6(2), Ag30(SCH2C10H7)18(Cr O4)2(DMAc)2(CF3CO2)8(3) and {[Ag12(SCH2C10H7)6(CF3CO2)4(CH3CN)6][Cr2O7]}n(4). Their structures and properties have been characterized. Evaporate of the reaction solution of the C10H7CH2 SH and CF3 COOAg in ethanol-DMAc(v : v = 1 : 1) produced pale yellow crystals of 2. Cluster 2 emits yellow light in the solid state at 77 K and is not emissive at room temperature. Instead, with the addition of K2Cr2O7, cluster 3 was obtained with a peanut-shaped cage-like structure that was doubly templated by two Cr O42- ions, and an intense broad absorption band was found in the range of 200–600 nm. Under the same conditions, by changing solvent we got compound 4, which shows a chain-like intercluster structure. This suggests that the solvent to template induced the formation of high-nuclearity clusters plays an important role. Our presented work is an important milestone in the field of the high-nuclearity cluster, as it fills in the blanks of the silver chalcogenide clusters.3 、 We report the syntheses and crystal structures of Ag12(SCH2C10H7)6(CF3CO2)6(C5H5N)6(5), Ag12(SCH2C10H7)6(CF3CO2)6(C5H5N)6(6), Ag12(SCH2C10H7)6(CF3CO2)4(OH)2(C12N2H8)6(7), Ag12(SCH2C10H7)6(CF3CO2)6(C9NH7)6(8), Ag12(SCH2C10H7)6(CF3CO2)6(C9H6NOH)6(9) and Ag12(SCH2C10H7)6(CF3CO2)6(C11N3H9)6(10). These compounds were synthesized by the reaction of C10H7CH2 SH, ancillary nitrogen ligand, and CF3 COOAg at room temperature. Their structures have been characterized by single crystal X-ray diffraction. Under the condition of different auxiliary nitrogen ligands, we got a series of silver chalcogenide nanoclusters with novel structures, and every silver chalcogenide nanocluster has a Ag12 cluster skeleton. In the field of silver chalcogenide nanoclusters with auxiliary nitrogen ligands, the work is of great significance.