Thiolato Protected Copper Sulfide Cluster with the Tentative Composition Cu₇₄S₁₅(2-PET)₄₅

Abstract

Ligand protected copper nanoclusters with precise compositions have attracted considerable attention due to their unique photoluminescent properties. However, the acquisition of structural information, knowledge of the factors affecting the stability, and high quantum yields are prerequisites for assessing their applications in biomedicine as fluorescent contrast agents, biosensors, and probes for cells. Despite all the effort, only finite examples of single crystal structures of CuNCs are reported. Herein, we report the phosphine-free synthesis and structure determination of 2-PET protected CuNCs. The structure analysis established by single crystal X-ray diffraction reveals the formation of binary Cu 74 S 15 (2-PET) 45 sulfide cluster. A similar phenomenon has been observed for several other chalcogenide-bridged copper clusters. The synthesized cluster possesses a rod-like structure, protected with 45 thiol ligands on the surface. Fifteen independent bridged-sulfur atoms couple to the copper atoms inside the core. Calculations for both a neutral and negatively charged cluster showed no major differences in their geometrical structures. Further analysis of frontier MO levels of the closed-shell anion predicts the HOMO−LUMO transition to be intramolecular L7 → L1 charge transfer, where "L7" and "L1" abbreviations refer to the corresponding sulfur layer in the structure. For the neutral cluster, the calculated spin density is delocalized over the two moieties. On the basis of TDDFT+TB calculations, the onset of the measured absorption spectrum could be satisfactorily reproduced.

Copper nanoclusters: designed synthesis, structural diversity, and multiplatform applications

“…Recently our group reported the structure of a Cu74S15(2-PET)45 (2-PET = 2-phenylethanethiol) cluster with similar Cu deficiencies. 195 The reduction of a copper salt with 2-PET ligand was completed with the addition of triethylamine (TEA) as a base. The crystallization of the sample from the saturated solution resulted in the formation of dark reddish orange crystals.…”

“…The entire metallic framework is protected with cyclohexylmonothiocarbonate ligands binding in a bridging mode. Hayton and co-workers recently reported a novel synthetic strategy for the preparation of "atlas-sphere"- 153 and in 2020 by Burgi and co-workers, 195 respectively. Note, the former cluster also contains phosphine ligands in the ligand shell whereas in the last case the Cu74 core contains 15 sulphur atoms incorporated into the metallic framework which is further protected with 45 thiolate (in this case 2-PET: 2-phenylethylthiol) ligands ( Fig.…”

[Cu32(PET)24H8Cl2](PPh4)2: A Copper Hydride Nanocluster with a Bisquare Antiprismatic Core

“…In addition to thiolates, phosphines, halides, dithiocarbamates, sulfides, carboxylates, hydrides, alkynes or their combinations are potential ligands for Cu NCs. 3,[22][23][24][25][26][27][28][29][30] It has long been considered that the protecting ligands deactivate the catalytic activity of metal NCs as well as block the reactants from approaching metal sites. 13,31 Partial or complete ligand removal is suggested for marking appreciable activity by compromising the size and structure of NCs.…”

Aggregation of Surface Structure Induced Photoluminescence Enhancement in Atomically Precise Nanoclusters

“…Metal nanoclusters have served as an emerging class of modular nanomaterials [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and have attracted intensive research interest due to their atomically precise structures [20][21][22][23][24][25][26][27][28][29][30][31][32] and intriguing physical-chemical properties. [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] Among these properties, photoluminescence (PL) is one of the most fascinating, both theoretically and experimentally, due to the plethora of promising PL-based applications.…”