Tkachuk O. Interaction of lanthanoid shift reagents with bifunctional flavones

The interaction of the lanthanide shift reagents with different derivatives of flavones has been studied. This type of interaction causes such kinds of anomalies as line broadening, causing by exchange process; abnormal influence of leading group; the conformation changes; unusual direction of magnetic axis. Those anomalies can be explained by chelating effects. It has been studied with some derivatives of 2-alkoxychalcones, 3-thiazolyl-4-thioxochromones and chromone-2-yl-tiazolyl tosilates. It was shown that the coordination of different LSR could occur in different ways. While Yb(fod)3 is coordinated mainly to one coordination center - with the carbonyl oxygen atom or heterocyclic nitrogen atom, Eu(fod)3 react with the studied substances as with bidentate ligands forming tetrakischelates. The possibility of the chelating is influenced by the sterical hindrance near the coordination centers of the substrate molecule and electronic character of substitutes. The chelating with LSR strongly influences the conformation equilibrium of molecules in the solution.By interaction of Eu(fod)3 and Yb(fod)3 with chromone-2-yl-tiazolyl tosilates isostructural complexes it was formed. This causes lack of chelating effect. The lanthanide ions location is determined by sterical hindrance in chromone and thiazol ring. The chromones ring conformation relative to thiazole ring was found. It was shown the conclusions made on the grounds of induced shift were in consistency with theoretical calculations.