Armed-azacrown ethers having dual binding sites in a side arm: Complexing abilities and crystal structure of two alkali-metal complexes

New armed-monoaza-12-crown-4 and armed-monoaza-15-crown-5 ethers having dua l phenolic OH and pyridine nitrogen binding sites in a side arm were prepar ed by the Mannich reaction of N-methoxymethyl-monoazacrown ethers with 3-hy droxypyridine. Complexation studies of these new hydroxypyridine-armed liga nds were carried out by liquid membrane transport,H-1 nmr titration experim ents, thermodynamic values (log K, DeltaH and T DeltaS), and X-ray crystall ography of two alkali-metal complexes. These results indicate that the oxyg en atom of the phenolic OH group and pyridine nitrogen atom of the side arm are involved in complexation under basic and neutral conditions, respectiv ely.