Allosteric Manipulation of Photoexcited State Relaxation in a Series of Ru II (bpy) 2 (bipyridine−crown ethers)

A series of ruthenium( II ) crown ether complexes containing 4‐, 5‐, or 6‐oxygen crowns tethered to a bipyridine at the 3,3′ position were prepared and examined for their ability to act as luminescent sensors. The complexes [(bpy) 2 Ru(2,2′‐bipyridine‐3,3′‐16‐crown‐4)](PF 6 ) 2 and [(bpy) 2 Ru(2,2′‐bipyridine‐3,3′‐19‐crown‐5)](PF 6 ) 2 were characterized by X‐ray crystallography. The 4‐oxygen crown crystallizes in the P $\bar 1$ space group. The 5‐oxygen crown crystallizes in the P $\bar 1$ space group. In both complexes, the inter‐pyridine ring angle in the tethered bipyridine is twisted substantially away from 0°. Coordination of a heavy metal ion such as Pb 2+ by the crown ether, and the geometric changes that result, were examined by UV/Vis, luminescence and NMR spectroscopy. The results show that there is a weak allosteric interaction between the Pb 2+ ion and the Ru complexes, and that this interaction alters the luminescent behavior of the Ru complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)