Stable 8-Hydroxyquinolinate-Based Podates as Efficient Sensitizers of Lanthanide Near-Infrared Luminescence

详细信息    查看全文

• 作者：Steve Comby ; Daniel Imbert ; Anne-Sophie Chauvin ; and Jean-Claude G. B&uuml ; nzli
• 刊名：Inorganic Chemistry
• 出版年：2006
• 出版时间：January 23, 2006
• 年：2006
• 卷：45
• 期：2
• 页码：732 - 743
• 全文大小：266K
• 年卷期：v.45,no.2(January 23, 2006)
• ISSN：1520-510X

文摘

New polydentate ligands (e.g., <B>Tsox and TsoxMe) have been synthesized to take advantage of the chelatingeffect of bidentate 8-hydroxyquinolinate subunits connected to a N,N,N',N'-tetraaminopropyl-1,2-ethylenediamineframework and with the aim of sensitizing the NIR luminescence of Nd^III and Yb^III ions. Ten pK_a's have beendetermined and the interaction between the ligands and Ln^III ions in dilute aqueous solution has been probed bothby potentiometric and spectrophotometric titrations. These studies have been mostly performed with the Eu^III ion,which is in the middle of the lanthanide series, and extended to other ions (La^III, Er^III, Lu^IIII). Stable complexes withLn^III ions are formed (pLn in the range of 14-16), the four chromophoric units being coordinated to the metalcenter, exploiting the entropic effect generated by the anchor. The monometallic complexes [Ln(H₂L)]^3- exist asthe major species at physiological pH regardless of the lanthanide used. Lifetime determinations of the Nd(⁴F_3/2)and Yb(²F_5/2) excited levels in both H₂O and D₂O at buffered pH point to the absence of water molecules boundin the inner coordination sphere of the Ln^III. Photophysical properties of the free ligands and of their lanthanidecomplexes have been investigated in buffered aqueous solutions both at room temperature and 77 K. The low-energy triplet state makes energy transfers from the ligand to the metal ions possible; this leads to a sizablesensitization of the Nd^III- or Yb^III-centered luminescence (bscribe/journals/inocaj/45/i02/eqn/ic0515249e10001.gif"> = 0.02% and bscribe/journals/inocaj/45/i02/eqn/ic0515249e10002.gif"> = 0.18%) for Tsox chelates.Methylation of the amide functions removes the quenching mechanism induced by the proximate N-H vibrationsand increases both the lifetimes and quantum yields of the TsoxMe chelates (bscribe/journals/inocaj/45/i02/eqn/ic0515249e10003.gif"> = 0.04% and bscribe/journals/inocaj/45/i02/eqn/ic0515249e10004.gif"> = 0.37%).In fact, TsoxMe yields one of the most luminescent Yb^III compounds known in water, and this ligand appears tobe suitable for the development of NIR probes for bioanalyses.