Síntese e utilização de compostos heterocíclicos da classe 1,3,4-Tiadiazólio como sondas fluorescentes

Abstract

Mesoionic compounds are heterocycles whose not classical structures have been considered of interest, specially because of their potential biological activity. Heterocyclic compounds of 1,3,4-thiadiazolium-2-phenilamine system, the mesoionic compounds precursors were synthetized with well known fluorescent groups bound to the C-5 of the heterocycle, using the anhydroacylation of the 1,4-diphenylthiosemicarbazide. The products obtained were 5-X-4-phenil-l,3,4-thiadiazolium-2-phenilamine where X = benzyl, naphtyl, a-acetylnaphtyl, a-acetilpirenyl and cinamoil, MICO-1, MICO-2, MICO-3, MICO-4 and MICO-5, respectively. MICO-2, MICO-3 and MICO-4 compounds were not described in the literature. Ali of these compounds, including MICO-1 and MICO-5 were characterized by spectroscopy using infrared, ultraviolet and RMN 1H and 13C techniques. An structural isomer of MICO-1, the 1,4,5-triphenyl-1,3,4-triazolium-2-thio (MICO-6) was obtained by the reflux of the corresponding thiadiazolium in pyridine, characterized by the same spectroscopic techniques. The UVNIS emission spectra of these compounds showed significative fluorescênce only for the 1,3,4-thiadiazolium system derivatives. Corresponding mesoionics to each of the conjugated acids, BMICO-1, BMICO-2, BMICO-3, BMICO-4, BMICO-5 and BMICO-6, were prepared by the adition of NaOH to acetonitrile solution containing these acids. Free bases were not isolated, and their characterization were done by UV/VIS spectroscopy. Fluorescence emission spectra of calf thymus ADN were obtained in the presence or absence of these twelve compounds. Data showed a significative interaction of the compounds and the biomolecule.