Near-Infrared Luminescence of Nine-Coordinate Neodymium Complexes with Benzimidazole-Substituted 8-Hydroxyquinolines

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• 作者：Nail M. Shavaleev ; Rosario Scopelliti ; Fré ; dé ; ric Gumy ; Jean-Claude G. Bü ; nzli
• 刊名：Inorganic Chemistry
• 出版年：2008
• 出版时间：October 6, 2008
• 年：2008
• 卷：47
• 期：19
• 页码：9055-9068
• 全文大小：396K
• 年卷期：v.47,no.19(October 6, 2008)
• ISSN：1520-510X

文摘

A new class of benzimidazole-substituted 8-hydroxyquinoline ligands has been prepared that contain a monoanionic tridentate N,N,O-coordinating unit. These ligands form charge-neutral lanthanide complexes of the type [Ln(L-R)₃]·nH₂O or [Ln₂(L2)₃]·nH₂O (n = 1−3) with early lanthanides from La^III to Gd^III inclusive. Crystallographic characterization was carried out for 11 complexes with 6 different ligands. In all of these structures, the lanthanide ion was found to be nine-coordinated by three ligands arranged in an “up−up−down” fashion around the metal center. The coordination environment can be described as a tricapped trigonal prism, with N atoms of quinoline rings occupying capping positions. Upon deprotonation of the ligand and complex formation, a new absorption band appears in the visible range of the spectrum with a maximum in the range of 466−483 nm and molar absorption coefficient of (7.2 − 18) × 10³ M⁻¹ cm⁻¹. Its origin is likely to be an intraligand phenolate-to-pyridyl charge transfer transition centered on the 8-hydroxyquinolate chromophore. Upon excitation in ligand absorption bands, new Nd^III complexes display characteristic metal-centered luminescence in the near-infrared region from 850 to 1450 nm with quantum yields and lifetimes in solid state at room temperature as high as 0.34% and 1.2 μs, respectively.