夹心三明治结构的二十五核银硫簇合物[Ag25(SC6H4Pri)18 (dppp)6](CF3SO3)7·CH3CN：结构表征及光学性能

在本研究中，使用(ⁱPrC₆H₄SAg)_n作为合成银硫纳米簇合物的前驱体。当存在辅助的双膦配体1, 3-双(二苯基膦)丙烷(dppp)及可溶性银盐(CF₃SO₃Ag)，在超声合成条件下，获得了一例二十五核银硫簇合物Ag₂₅，并借助X射线单晶衍射技术确定相应的分子结构。该银硫簇合物具有夹心三明治的骨架结构：分别由两个结构相似的圆柱体共享一个七核纯银簇所构成的金属簇平面。固态紫外可见漫反射光谱测试表明该簇合物的能级带隙为2.5 eV，属于半导体材料的范畴。固态发光测试显示，该簇合物在室温下发射绿光。

[Ag25(SC6H4Pri)18(dppp)6](CF3SO3)7·CH3CN (HSC6H4Pri = 4-t-isopropylthiophenol,and dppp = 1, 3-bis(diphenyphosphino)propane) Cluster Containing a Sandwich-like Skeleton: Structural Characterization and Optical Properties

Crystalline silver cluster compounds are highly interesting owing to their intriguing structure and potential technological application in luminescence, semiconductivity, and as precursors for nonlinear optical materials. Typically, the synthesis of silver clusters involves the use of protecting ligands such as thiolates, phosphines, and alkynes, which have been found to be critical for cluster size and shape tuning. Among these nanoclusters, pentacosanuclear silver clusters (Ag₂₅) have only been reported with either thiolate ligands or phosphine ligands, while those bearing mixed protecting ligands are rather rare. In the course of our exploration of novel silver clusters, a new silver thiolate precursor (ⁱPrC₆H₄SAg)_n was used to construct nanosized silver clusters. In the presence of 1, 3-bis(diphenyphosphino)propane (dppp) and CF₃SO₃Ag, the pentacosanuclear silver cluster [Ag₂₅(SC₆H₄Prⁱ)₁₈(dppp)₆](CF₃SO₃)₇·CH₃CN (designated as Ag₂₅, HSC₆H₄Prⁱ = 4-t-isopropylthiophenol) ligated both by thiolate and phosphine ligands was obtained under ultrasonic reaction conditions. Yellow block crystals were isolated from the solution, whose molecular structure was elucidated by single-crystal X-ray analysis. The skeleton of the Ag₂₅ cluster comprises a sandwich-like motif containing two structurally very similar cylinders sharing a metal-cluster plane. The core of each cylinder presents the overall shape of a twisted hexagonal cylinder made of two connected Ag₃S₃ units, with six sulfur atoms and six silver atoms alternating on a puckered drum-like surface. The metal-cluster plane contains one type of pure-Ag tetragons showing significant Ag…Ag argentophilic interactions. The optical properties of Ag₂₅ were investigated in the solid state. A band gap of ~2.5 eV was estimated for Ag₂₅ from the optical absorption spectrum, suggesting this cluster to be a potential wide-gap semiconductor. This Ag₂₅ cluster was also found to emit green luminescence at λ = 505 nm and room temperature.