NEW HYBRID XANTHENE-PYRYLIUM DYES: SYNTHESIS AND SPECTRAL PROPERTIES

In this work we studied the interaction of N'-(4-formyl-2,3-dihydro-1H-xanthen-9-yl)-N,N-dimethylimidoformamide with 2,6-di-tert-butyl-4-methylpyrylium perchlorate and 2-methyl-4,6-diphenylpyrylium tetrafluoroborate in acetic anhydride under various conditions. Thus, when carrying out the reaction with 2,6-di-tert-butyl-4-methylpyrylium perchlorate at 100 °C for 6 h, the corresponding dye is formed with the amidine group replaced by acetyl. In the case of carrying out the reaction with 2-methyl-4,6-diphenylpyrylium tetrafluoroborate at room temperature for 1 h, the dye is formed with the amidine fragment preserved. The absorption spectra of the obtained dyes were recorded in various solvents and the extinction coefficients were calculated. The absorption maximum of 4-{(E)-2-[9-(acetylamino)-2,3-dihydro-1H-xanthen-4-yl]vinyl}-2,6-di-tert-butylpyrylium perchlorate in toluene and chloroform is approximately 675 nm, whereas in water it is hypsochromically shifted to 605 nm. The absorption coefficient of this dye in chloroform is observed to be the highest, with a value that is 5-7 times higher than that in water or toluene. A modification in the polarity of the solvent exerts minimal influence on the absorption maximum of 2-[(E)-2-(9-{[(1E)-(dimethylamino)methylene]amino}-2,3-dihydro-1H-xanthen-4-yl)vinyl]-4,6-diphenylpyrylium tetrafluoroborate, which is situated at approximately 715 nm.