Dual Emission Caused by Ring Inversion Isomerization of a 4-Methyl-2-pyridyl-pyrimidine Copper(I) Complex

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• 作者：Michihiro Nishikawa ; Kuniharu Nomoto ; Shoko Kume ; Keiichi Inoue ; Makoto Sakai ; Masaaki Fujii ; Hiroshi Nishihara
• 刊名：Journal of the American Chemical Society
• 出版年：2010
• 出版时间：July 21, 2010
• 年：2010
• 卷：132
• 期：28
• 页码：9579-9581
• 全文大小：166K
• 年卷期：v.132,no.28(July 21, 2010)
• ISSN：1520-5126

文摘

We developed a new convertible copper(I) complex using 2-pyridyl-4-methylpyrimidine and diphosphine as ligands. This complex exhibited mechanical bistability based on the inversion motion of the pyrimidine ring, leading to dual luminescence behavior. The inversion dynamics was strongly dependent on temperature and solvent. Variable-temperature ¹H NMR spectra revealed that the two isomers interconverted in solution via ring inversion, and the motion was frozen below 200 K. The complex exhibited characteristic CT absorption and emission bands in solution. Emission lifetime measurements demonstrated that the emission could be deconvoluted into two components. The fast and slow components were assigned to the two isomers, the excited states of which were characterized by different structural relaxation process and/or additional solvent coordination properties. The emission properties of the two isomers differed not only in lifetime and wavelength but also in heat sensitivity. The molar ratio of the two isomers varied with the polarity of the solvent via electrostatic interactions with the counteranion. The rate of inversion was affected by solvent, suggesting that inversion was promoted by solvent coordination.