Rare‐Earth Nitroquinolinates: Visible‐Light‐Sensitizable Near‐Infrared Emitters in Aqueous Solution

Water‐soluble, stable, and easily synthesizable 1:4 complexes of rare‐earth ions with 8‐hydroxy‐5‐nitroquinolinate ligands have been prepared. These complexes can be sensitized by visible light with wavelengths up to 480 nm and show near‐infrared emission in aqueous solution. The incorporation of a nitro group in the quinoline moiety shifts its absorption bands to longer wavelengths and also increases its molar absorptivity by a factor of 2.5, thereby significantly enhancing its light‐harvesting power. The presence of the nitro group also increases the solubility of the resulting complexes, making them water‐soluble. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)