Журнал "Макрогетероциклы"

The synthesis of ABBB-type macroheterocyclic compound containing both the 5-amino-2-dodecyl-3-imino-1,2,4-thiadiazoline fragment (fragment A) and three residues of 1,3-diiminoisoindoline (fragment B) is described in this work. The purification of target compound was carried out by column chromatography and by silica gel plate eluting with CH₂Cl₂:MeOH:C₆H₁₄ mixture. The structure of the resultant compound was determined by data of UV-Vis, IR, ¹H and ¹³C NMR spectroscopy, and mass spectrometry. It was shown that the target product possesses unique stability in acid medium and can belong to the class of "molecular chameleons" due to its ability postsynthetic modification of the optical properties of molecule. A bathochromic shift of the absorption maximum at 459–555 nm and emergence of new inflection points at 692 and 721 nm in trifluoroacetic acid and a shift to 716 nm in sulfuric acid were observed in the UV-visible spectrum. Acid-base behavior has been studied by spectrophotometric titration method in two solvent systems: СН₂Cl₂–CF₃COOH and C₂H₅OH–H₂SO₄. The study of protonation in the first solvent system shows an interaction between one molecule of the macroheterocycle with one molecule of the acid. Investigations of the second medium demonstrated the presence of one non-protonated (λ=478 nm) and two protonated (λ=550 nm, λ=716 nm) forms. The most possible position of protonation was determined by quantum chemical calculations at the DFT level.