Benzoid-quinoid tautomerism of azomethines and their structural analogs: LIV. Dibenzo(benzo)-18-crown-6-containing Imines of 5-hydroxy-2,3-tetramethylene- and 5-Hydroxy-2,3-diphenylbenzo[<Emphasis Type="Italic">b</Emphasis>]furan-4-carbaldehydes

Dibenzo(benzo)-18-crown-6-containing N-arylimines of 5-hydroxy-2,3-tetramethylene- and 5-hydroxy-2,3-diphenylbenzob]-furan-4-carbaldehydes were synthesized and their spectral luminescence properties were investigated. In solutions of 6-bromo- and 6-nitro-substituted compounds a tautomeric equilibrium exists between the benzoid and quinoid forms. In the course of complexing of crown-ether-imines of 5-hydroxy-6-nitro-2,3-diphenylbenzob]furan-4-carbaldehyde and 5-hydroxy-6-nitro-2,3-tetramethylenebenzob]furan-4-carbaldehyde with cations of alkali and alkaline earth metals the content of the quinoid form was found to decrease. This phenomenon was accompanied by essential changes in the absorption and fluorescence spectra characteristic of chemosensor systems with an intramolecular charge transfer (ICT).