Suchergebnisse

The sensing behaviour toward metal cations and biothiols of two 2,4,5-triarylimidazole probes (3a and 3b) is tested in acetonitrile and in acetonitrile-water. In acetonitrile the two probes present charge-transfer absorption bands in the 320-350 nm interval. Among all cations tested only Cu(11) is able to induce bathochromic shifts of the absorption band in the two probes, which is reflected in marked colour changes. Colour modulations are ascribed to the formation of 1:1 Cu(II)-probe complexes in which the cation interacts with the imidazole acceptor heterocycle. Besides, the two probes present intense emission bands (at 404 and 437 nm for 3a and 3b respectively) in acetonitrile that are quenched selectively by Cu(11). Probe 3a is soluble in acetonitrile-water 1:1 (v/v) and Cu(11) also induces bathochromic shifts of the absorption bands. Moreover, the emission bands of probe 3a in this mixed aqueous solutions is quenched in the presence of Cu(II). The potential use of the 1:1 complex formed between 3a and Cu (II) for the chromo-fluorogenic detection of biothiols (GSH, Cys and Hcy) in aqueous environments is also tested. At this respect, addition of GSH, Cys and Hcy to acetonitrile-water 1:1 v/v solutions of 3a-Cu(11) complex induces a hypsochromic shift of the visible band (reflected in a bleaching of the solutions) with a marked emission increase at 470 nm. ; We thank the Spanish Government (MAT2015-64139-C4-1-R) and Generalitat Valenciana (PROMETEO 2018/024). H.E.O. thanks Generalitat Valenciana for his Grisolia fellowship. Thanks are also due to Fundação para a Ciência e Tecnologia (Portugal) for financial support to the Portuguese NMR network (PTNMR, Bruker Avance III 400-Univ. Minho), FCT and FEDER (European Fund for Regional Development)-COMPETEQREN-EU for financial support to the research centre CQ/UM [Ref. UID/QUI/00686/2013 and UID/QUI/0686/2016], and a PhD grant to R.C.M. Ferreira ...

A new simple and easy-to-prepare imidazole-based probe 1 was synthesized and used to detect Cu(II) and biothiols (Cys, Hcy and GSH) in aqueous environments. Addition of increasing amounts of Cu(II) to water (pH 7.4)-acetonitrile 90:10 v/v solutions of probe 1 induced the apperance of a red-shifted absorption together with a marked colour change from colorless to deep blue. In addition, probe 1 was fluorescent and a marked emission quenching in the presence of Cu(II) was observed. The optical response is selective and other cations tested do not induce significant chromo-fluorogenic modulations. Limits of detection for Cu(II) of 0.7 and 3.2 μM using UV–visible and fluorescence data were determined. On the other hand, addition of Cys, Hcy and GSH to the deep-blue water (pH 7.4)-acetonitrile 90:10 v/v solutions of the 1-Cu(II) complex reulted in a marked bleaching together with the appearance of a highly emissive band centred at 475 nm. Other amino acids tested induced negligible response. The limits of detection for Cys, Hcy and GSH using 1-Cu(II) and emission data are 6.5, 5.0 and 10.2 μM, respectively. These optical changes were ascribed to a biothiol-induced demetallation process of the 1-Cu(II) complex that released the free probe. Besides, probe 1 is non-toxic and can be used for Cu(II) detection in HeLa cells. ; FCT - Generalitat Valenciana(PROMETEOII/2014/047); Spanish Government (projects MAT2015-64139-C4-1-R and AGL2015-70235-C2-2-R) and the Generalitat Valenciana (project PROMETEOII/2014/047). Thanks are also due to Fundação para a Ciência e a Tecnologia for financial support to the Portuguese NMR network (PTNMR, Bruker Avance III 400-Univ. Minho), FCT and FEDER (European Fund for Regional Development)-COMPETEQREN-EU for financial support to the research centre CQ/UM (Ref. UID/QUI/00686/2013 and UID/QUI/0686/2016), and a PhD grant to R. C. M. Ferreira (SFRH/BD/86408/2012) ...

Herein, three N,N-diphenylanilino-heterocyclic aldehyde probes (5, 6 and 7) are synthesized, characterized and their sensing behaviour against metal cations tested. Acetonitrile solutions of the three probes show an intramolecular charge-transfer band in the 360-420 nm range due to the presence of an electron donor N,N-diphenylanilino group and an electron acceptor aldehyde moiety. Besides, all three probes are moderately emissive with bands in the 540-580 nm range in acetronitrile. The chromo-fluorogenic behaviour of the three probes in acetonitrile in the presence of selected metal cations is assessed. Of all the metal cations tested only Cu(ii) induces marked colour and emission changes. In this respect, addition of Cu(ii) cations to solutions of the probes induces the appearance of NIR absorptions at 756 nm for 5, at 852 nm for 6 and at 527, 625 and 1072 nm for 7. Besides, Cu(ii) induces a marked quenching of the emission of the three probes. The observed spectral changes are ascribed to the formation of 1:1 probe-Cu(ii) complexes in which the metal cation interacts with the acceptor part of the chemosensors. In addition, the limits of detection determined using UV-visible and fluorescence titrations are in the 0.21-5.12 M range, which are values lower than the minimum concentration prescribed by the World Health Organization (WHO) guideline for drinking water for copper (30 mM). Besides, probe 7 is used for the detection of Cu(ii) in aqueous environments using SDS anionic surfactant. ; We thank the Spanish Government (MAT2015-64139-C4-1-R) and Generalitat Valenciana (PROMETEO2018/024). H. E. O. thanks Generalitat Valenciana for his Grisolia fellowship. Thanks are due to Fundação para a Ciência e Tecnologia (FCT) for a PhD grant to R. C. M. Ferreira (SFRH/BD/86408/2012), and FEDER (European Fund for Regional Development)-COMPETE-QREN-EU for financial support through the Chemistry Research Centre of the University of Minho (Ref. PEst-C/QUI/UI0686/2016 and PEst-C/QUI/UI0686/2018). The NMR spectrometer Bruker ...