High-Nuclear Organometallic Copper(I)-Alkynide Clusters: Thermochromic Near-Infrared Luminescence and Solution Stability

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• 作者：Hong-Yan Zhuo ; Dr. Hai-Feng Su ; Zhao-Zhen Cao ; Wei Liu ; Prof. Shu-Ao Wang ; Lei Feng ; Dr. Gui-Lin Zhuang ; Dr. Shui-Chao Lin ; Prof. Mohamedally Kurmoo ; Prof. Chen-Ho Tung ; Dr. Di Sun and Prof. Lan-Sun Zheng
• 刊名：Chemistry - A European Journal
• 出版年：2016
• 出版时间：December 5, 2016
• 年：2016
• 卷：22
• 期：49
• 页码：17619-17626
• 全文大小：2139K
• ISSN：1521-3765

文摘

Cu(CF₃COO)₂ reacts with tert-butylacetylene (tBuC≡CH) in methanol in the presence of metallic copper powder to give two air-stable clusters, [Cu^I₁₅(tBuC≡C)₁₀(CF₃COO)₅]⋅tBuC≡CH (1) and [Cu^I₁₆(tBuC≡C)₁₂(CF₃COO)₄(CH₃OH)₂] (2). The assembly process involves in situ comproportionation reaction between Cu²⁺ and Cu⁰ and the formation of two different clusters is controlled by reactants concentration. The clusters consist of Cu₁₅ and Cu₁₆ cores co-stabilized by strong by σ- and π-bonded tert-butylethynide and CF₃COO⁻ (together with methanol molecule in 2). Their stabilities in solution were confirmed using electrospray ionization mass spectrometry in which the cluster core remains intact for 1 in chloroform and acetone, and for 2 in acetonitrile. Strong thermochromic luminescence in the near infrared (NIR) region was observed in the solid-state. Of particular interest, the emission maximum of 1 is red-shifted from 710 nm at 298 K to 793 nm at 93 K, along with a 17-fold fluorescence enhancement. In contrast, 2 exhibits red shift from 298 to 123 K followed by blue shift from 123 to 93 K. The emission wavelength was correlated with the structural parameters using variable-temperature X-ray single-crystal analyses. The rich cuprophilic interaction plays a significant role in the formation of ³LMCT (tBuC≡C→Cu_x) excited state mixed with cluster-centered (³CC) characters, which can be considerably influenced by temperature, leading to thermochromic luminescence. The present work provides 1) a new synthetic protocol for the high-nuclear Cu^I–alkynyl clusters; 2) a comprehensive insight into the mechanism of thermochromic luminescence; 3) unusual emissive materials with the characters of NIR and thermochromic luminescence simultaneously.