Heterocyclic dicyanovinyl derivatives: synthesis and evaluation of the chemosensory ability in aqueous solution

Two novel dicyanovinyl derivatives 3a-b were synthesized in moderate to good yields through a Knoevenagel reaction of the corresponding aldehyde precursors and malononitrile. The photophysical properties of the new push-pull systems were studied by UV-vis and fluorescence spectroscopy in acetonitrile. The evaluation of the compounds as colorimetric chemosensors was carried out by performing spectrophotometric titrations in acetonitrile and acetonitrile/water in the presence of relevant organic and inorganic anions, and of alkaline, alkaline-earth and transition metal cations. The benzoindole derivative exhibited great selectivity for the cyanide anion over other anions in acetonitrile/water (8:2) solution showing a distinct color change from colorless to yellow.FCTFEDERQRE

Photophysical characterization and ion sensing properties of new colorimetric chemosensors based on hydrazones bearing quinoline

Molecular receptors are chemical species designed to achieve a high degree of complementarity with a selected guest. When synthetic receptors are coupled with certain signaling units, that could change one or more physical properties upon receptor-guest interaction (e.g. color, fluorescence, redox potential), a molecular sensor is obtained. In this field is especially appealing the use of optical outputs such as changes in color and/or fluorescence that allow the use of low-cost and widely available instrumentation. Moreover, in the case of chromogenic chemosensors, a straightforward semi-quantitative and in situ “naked-eye” detection is possible and chromo-fluorogenic chemosensors displaying a displacement of the absorption or emission bands are interesting for the development of ratiometric procedures. Hydrazone and quinoline derivatives have been reported to be suitable systems for the optical (colorimetric and fluorimetric) sensing of certain anions and for the recognition of metal cations. Other applications in materials science include molecular switches and OLEDs. Taking into account the above mentioned facts and our interest in the development of optical probes, we report herein the synthesis, photophysical characterization and interaction studies toward anions and cations, in ACN, of probes 2a-b containing hidrazono-quinoline moieties as both binding and signaling subunits. Moreover, selective detection of cyanide was achieved in aqueous mixtures for chemosensor 2a.FCTFEDERQRE

Synthesis, characterization and evaluation of the chemosensory ability of benzothiazolium salts bearing a triphenylamino donor group and an aryl spacer

Organic salts are the focus of much recent attention, in part due to their stability and the ease of tailoring for specific physical properties. In particular, styryl-pyridinium and benzothiazolium salts have been widely applied in diverse areas such as NLO-phores, frequency-upconversion, optical power limiting, fluorescent probes, laser scanning fluorescence microscopy, molecular switches, etc.1 The recognition and detection of ionic species has aroused great interest due to their important roles in many biological and environmental processes. Several sensor systems have been developed but most present some limitations in terms of sensitivity, selectivity, and simplicity. Colorimetric chemosensors are molecules that allow naked-eye detection of ionic species without resource to any instrumentation, offering qualitative and quantitative information. These chemical sensors are considered as one of the most effective analytical methods for environmental monitoring, particularly in the detection of metal ions whose presence in the environment has serious consequences. Additionally, chemosensors soluble in aqueous media are very interesting, because of the importance in sensing species in biological processes, disease states and environmental pollution.2 In this communication, we report the synthesis of two benzothiazolium salts 3a-b, substituted at position 2 with a triphenylamino donor group and an aryl spacer with different electronic character, in order to evaluate their photophysical properties and chemosensory ability. Organic salts 3 were synthesized through Knoevenagel reaction between the precursor aldehydes 2 and 1-methylbenzothiazolium salt 1 in moderate to good yields. The new derivatives were characterized by the usual techniques and a detailed photophysical study was undertaken. The evaluation of the compounds as colorimetric chemosensors was carried out by performing titrations in acetonitrile and acetonitrile/water in the presence of relevant organic and inorganic anions, and of alkaline, alkaline-earth and transition metal cations.Thank are due to Fundação para a Ciência e Tecnologia (Portugal) and FEDER-COMPETE for financial support through Centro de Química (PEst-C/QUI/UI0686/2013 (FCOMP-01-0124-FEDER-037302)), and a PhD grant to R.C.M. Ferreira (SFRH/BD/86408/2012). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased with funds from FCT and FEDER

Synthesis and evaluation of heterocyclic pyrrolidene imines as optical chemosensors

Imine derivatives are an important class of compounds due their biological and optical properties making them suitable for several applications such as chemosensor, photochromic, and others.[1,2] In recent years the search for new colorimetric chemosensors for anions has been of great interest because of the role that ions play in chemical and biological processes.[3] In this context and as part of an on-going research to develop efficient heterocyclic systems for photochromic and chemosensor applications [4] we report in this communication the synthesis, the photophysical characterization and the chemosensor ability of pyrrolidene heterocyclic imines functionalized with aryl or naphthyl moieties.Thanks are due to Fundacao para a Ciencia e Tecnologia (FCT-Portugal) and FEDER-COMPETE for financial support through Centro de Quimica [PEst-C/QUI/UI0686/2013 (FCOMP-01-0124-FEDER-037302)], PhD grants to M.C.R. Castro (SFRH/BD/78037/2011) and R.C.M. Ferreira (SFRH/BD/86408/2012). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased with funds from FCT and FEDER. We are also grateful to the Instituto da Educação of Universidade do Minho for providing the laboratory infrastructure necessary for the development of this work

Synthesis and evaluation of heterocyclic pyrrolidene imines as optical chemosensors

Imine derivatives are an important class of compounds due their biological and optical properties making them suitable for several applications such as chemosensors, photochromic compounds, among others. In recent years the search for new colorimetric chemosensors for anions has been of great interest because of the role that ions play in chemical and biological processes. In this context and as part of an on-going research to develop efficient heterocyclic systems for photochromic and chemosensory applications, we report the synthesis, the photophysical characterization and the chemosensory ability of pyrrolidene heterocyclic imines functionalized with aryl or naphthyl moieties. Keywords: Imines,FCTFEDERQRE

Ultrafast nonlinear effects in organic compounds and organic hybrids materials

Synthesis and solution-processing of specialized chemical compounds can facilitate the fabrication of nano-electronic devices. Many of these emerging applications require organic materials with well-characterized optical properties, specifically, large two-photon absorption (2PA) and nonlinear optical (NLO) responses. The most common strategy to achieve a strong second order nonlinear optical response is to link donor and acceptor moieties on opposite ends of a π-conjugated aromatic spacer. This configuration promotes spatial charge transfer and a strong difference in dipole moments between the ground and excited electronic states. Individual organic molecules, tailor made following this strategy, can often exhibit exceptionally large intrinsic nonlinear optical properties, but the translation to a macroscopic electro-optic activity is often extremely difficult. Roughly more than 80% of all π-conjugated organic molecules crystallize in centrosymmetric space groups producing materials with no second order bulk susceptibility. Our group has demonstrated that is possible overcome this restriction by embedding organic molecules, which normally crystallize in centrosymmetric structures, into nanostructured polymeric matrix. Recently, we observed greatly enhance the nonlinearities of nominally weak nonlinear materials when insert in a polymeric nanofibers, one-dimensional nanostructures. These types of nanostructures are attracting attention because of the unique optical interactions that arise from their sub wavelength size. To explore this phenomena in detail we take advantage of our state of the art custom built Fluorescence Lifetime Imaging Microscope (FLIM). The temporal resolution of the FLIM is about 25 picoseconds and less than a 1 micron of spatial resolution. This system allows us to monitor the effects of nano-structured environments and their localized optical response. Other systems of current interest in our research group are graphene quantum dots both in solution and dispersed in a thin film of PVA, the interaction of excited dye molecules with a single layer graphene surface and tailor designed molecules for two photon absorption in the near infrared portion of the spectrum.info:eu-repo/semantics/publishedVersio

2,4,5-Triaryl imidazole probes for the selective chromo-fluorogenic detection of Cu(II). Prospective use of the Cu(II) complexes for the optical recognition of biothiols

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 (SFRH/BD/86408/2012)

N,N-Diphenylanilino-heterocyclic aldehyde-based chemosensors for UV-vis/NIR and fluorescence Cu(II) detection

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 Avance III 400 is part of the National NMR Network and was purchased within the framework of the National Program for Scientific Re-equipment, contract REDE/1517/RMN/2005 with funds from POCI 2010 (FEDER) and FCT

A simple and easy-to-prepare imidazole-based probe for the selective chromo-fluorogenic recognition of biothiols and Cu(II) in aqueous environments

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)info:eu-repo/semantics/publishedVersio