Estudo de um sensor cromogênico aniônico fundamentado na competição entre uma merocianina e um ânion pelo calix[4]pirrol

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

This work has studied the assembly of a chromogenic sensor that uses as receptor calyx[4]pyrrole (CP), which is capable to recognize fluoride with high efficience, and two solvatochromic dyes, Brookers merocyanine (MB) and Reichardts dye (CR), as signalizing unity. The solutions of MB in acetonitrile, a low polarity medium, exhibit violet color. It was observed that the dye interacts with CP through hydrogen bonding (HB), generating a CP-MB complex, which modified the color in the solution to orange. The binding constant of the complex was determined, being equal to (5.660.34)103 dm3 mol-1. It was verified that the binding of MB with CP strongly diminishes with the addition of low amounts of water, which is a solvent that strongly interacts with those species by means of HB, making difficult the complexation of the phenolate group in the dye with the -NH pyrrole groups in the receptor site. The studies performed with CR have demonstrated that the addition of CP to the dye solution has very small effect on the UV/Vis spectrum of the dye, showing that if some CPCR is formed in acetonitrile, it should occur at very reduced concentrations, even in very large CP concentrations. Association of CP with many anions was also studied, using the UV/Vis technique and MB as signalizing unity. It was verified a change in the solution color from orange to violet when fluoride was added to CP-MB complex. Chloride and dihydrogenphosphate anions were responsible by a little change in the color of the solutions in comparison with fluoride. The solutions of CP containing MB have been made pale yellow in the presence of hydrogensulfate due to the fact that the anion protonates the dye, removing it from the receptor site. Thus, this system was capable to detect hydrogensulfate between all other utilized anions. No alterations in color or in the UV/Vis spectrum were observed when bromide, iodide and nitrate were added to the mixture of CP with MB in acetonitrile

ASSUNTO(S)

merocianina de brooker ensaios de deslocamento sensor cromogênico quimica displacement assays ânion calyx[4]pyrrole calix[4]pirrol chromogenic sensor anion brookers merocyanine Ânions; corantes; solução (química)

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