An NIR Emissive Donor-π-Acceptor Dicyanomethylene-4H-Pyran Derivative as a Fluorescent Chemosensor System towards Copper (II) Detection

A.K. thanks the Erasmus+ Programme of the European Union for a student mobility fellowship. Publisher Copyright: © 2022 by the authors.A novel donor-π-acceptor fluorescent dye as a chemosensor for Cu2+ ions is herein presented. The fluorophoric core consists of a 3,5-diphenyl-dicyanomethylene-4H-pyran (DCM), with extended styryl chains on positions 2 and 6, bearing terminal di-(2-picolyl)amine (DPA) groups for metal coordination. Optical characterization of the chemosensor dye reveals an absorption maximum at ca. 500 nm and a strong bathochromic shift in the emission, reaching ca. 750 nm in polar solvents. This solvatochromic behavior, which yields very large Stokes shifts (up to ~6700 cm−1), is characteristic of the strong intramolecular Charge Transfer (CT) nature of this chromophoric system. While the chemosensor has demonstrated no changes in its optical properties over a wide pH range (2–12), a strong quenching effect was observed upon Cu2+ coordination, with a 1:1 binding stoichiometry, indicating that only one DPA unit is capable of effectively chelating Cu2+, rendering the second DPA motif inactive. The binding constant was determined to be 7.5 × 107 M−1, indicating a very high sensitivity, and an LOD of 90.1 nM. Competition assays have demonstrated that the chemosensor is highly selective towards Cu2+, even in the presence of excesses of other mono- and di-valent cations. Co2+ and Ni2+ proved to be the strongest interferents, particularly in the luminescent response. Paper test-strips prepared with the embedded sensor showed a fluorometric response in the presence of different copper (II) concentrations, which attested to the potential of this chemosensor to be used in the determination of Cu2+ content in aqueous media, for in-field applications.publishersversionpublishe

Design of fluorescent chemosensors for Naproxen and ATP and subsequent immobilization in nanoparticles

In this work, the design and characterization of two fluorescent chemosensor dyes for two distinct analytes, respectively Naproxen and adenosine triphosphate (ATP), is fully described. For the first case (Naproxen chemosensor), the chemosensor dye consisted of styrylpyridinium fluorophore and the synthesis was performed in two reaction steps with relatively good yield. The sensing mechanism was based on twisted intramolecular charge transfer (TICT), with Naproxen inducing a fluorescence enhancement on the chemosensor. The limit of detection (LOD) for Naproxen was 0.054 mM. The sensor dye was used for the synthesis of polyacrylamide nanoparticles, PAA-NPs, with a diameter of 34 nm. The sensitivity of the PAA-NPs to Naproxen was decreased when compared to the free dye in solution with a LOD of 0.50 mM. Selectivity and competitive assays were performed and the obtained results indicate that the synthesized PAA-NPs can be used for rapid diagnosis of Naproxen overdose in human plasma samples. For the second case (ATP chemosensor), the sensor dye was based on a naphthalimide fluorophore and the synthesis comprised four reaction steps. The chemosensor presented a dipicolylamine unit able to complex with metal ions which allowed ATP binding, translated in a fluorescence enhancement of 2.3 fold. Results suggested that adenine appeared to present a preference in interaction with the naphthalimide fluorophore, probably through stacking interactions. The chemosensor was covalently immobilized onto amine surface-functionalized silica nanoparticles through NHS-ester activation. The obtained nanoparticles were found to have a hydrodynamic diameter of 126 nm. Their sensing properties towards ATP showed a significant decrease in sensitivity when compared to the dye in solution although sensing of concentrations in the low micromolar range was also found possible

A First Approach to the Study of Winsor & Newton’s 19th-Century Manufacture of Madder Red Lake Pigments

Funding Information: We are grateful to Winsor & Newton, ColArt Fine Art & Graphics Ltd., for allowing the creation of the archive project. The W&N 19th Century Archive Database, designed by Mark Clarke and Leslie Carlyle, was funded by the Netherlands Institute for Scientific Research (NWO) as part of the De Mayerne Programme and, in the UK, by a Resource Enhancement Grant from the Arts and Humanities Research Council (AHRC). We thank Marta F. Campos for purchasing the Rose Madder 19th-century oil paint tube on eBay and dating it. We also appreciate the comments of the participants at the Dyes in History and Archaeology 41. Funding Information: This work was funded by the Portuguese Foundation for Science and Technology (FCT) of the Ministry of Science, Technology and Higher Education (MCTES) through the Research Units VICARTE (UIDB/00729/2020; UIDP/00729/2020) and LAQV-REQUIMTE (UIDB/50006/2020; UIDP/50006/2020), project MAGICA (PTDC/ART-PER/1702/2021), project REDiscover (2022.02909.PTDC), Vanessa Otero’s 2020.00647.CEECIND and Paula Nabais’s 2021.01344.CEECIND. Publisher Copyright: © 2023 by the authors.This paper focuses on the first investigation of the 19th-century manufacture of red lake pigments obtained from madder by Winsor & Newton (W&N), prominent artists’ colourman at that time. The first approach to their manufacture was carried out by studying the madder entries of the company’s book P1, found in the W&N 19th Century Archive Database. Eleven production records were discovered under names such as Rose Madder, Madder Carmine, Madder Lake and Madder Rose. Three main methods of synthesis were identified and reproduced, revealing three main steps: washing of the madder roots (Rubia tinctorum L.); extraction in acid media and complexation with Al3+ using alum; and precipitation by the addition of salts such as ammonium carbonate and sodium borate. The syntheses were followed by UV-VIS spectroscopy, and the pigments were further characterised by colourimetry, Energy-Dispersive X-Ray Fluorescence Spectrometry (XRF), Fourier Transform Infrared Spectroscopy (FTIR) and High-Performance Liquid Chromatography-Diode Array Detector (HPLC-DAD). They all exhibited a rose hue in a highly insoluble aluminate matrix. Although the dye extraction was incomplete, alizarin, purpurin and pseudopurpurin were identified. An analytical comparison with a Rose Madder 19th-century oil paint tube was also performed by micro-FTIR and microspectrofluorimetry. This work intends to be foundational to a systematic study of the W&N’s 19th-century madder colours aiming to contribute new knowledge towards their identification and preservation in heritage objects.publishersversionpublishe

Colorimetric and Fluorescent Sensing of Copper Ions in Water through o-Phenylenediamine-Derived Carbon Dots

Funding Information: This work was supported by Regione Lazio through Progetto di Ricerca POR FESR LAZIO 2014–2020 Id: A0375-2020-36403 according to G09493 del 14 July 2021. M.A. has been supported by MIUR—Ministero dell’Istruzione Ministero dell’Università e della Ricerca (Ministry of Education, University and Research) under the national project FSE/FESR–PON Ricerca e Innovazione 2014–2020 (N° AIM1887574, CUP: E18H19000350007). This research was also supported by Fundação para a Ciência e Tecnologia, FCT/MCTES, through the Associate Laboratory for Green Chemistry—LAQV (grants UIDB/50006/2020 and UIDP/50006/2020). Publisher Copyright: © 2023 by the authors.Fluorescent nitrogen and sulfur co-doped carbon dots (NSCDs) were synthesized using a simple one-step hydrothermal method starting from o-phenylenediamine (OPD) and ammonium sulfide. The prepared NSCDs presented a selective dual optical response to Cu(II) in water through the arising of an absorption band at 660 nm and simultaneous fluorescence enhancement at 564 nm. The first effect was attributed to formation of cuprammonium complexes through coordination with amino functional groups of NSCDs. Alternatively, fluorescence enhancement can be explained by the oxidation of residual OPD bound to NSCDs. Both absorbance and fluorescence showed a linear increase with an increase of Cu(II) concentration in the range 1–100 µM, with the lowest detection limit of 100 nM and 1 µM, respectively. NSCDs were successfully incorporated in a hydrogel agarose matrix for easier handling and application to sensing. The formation of cuprammonium complexes was strongly hampered in an agarose matrix while oxidation of OPD was still effective. As a result, color variations could be perceived both under white light and UV light for concentrations as low as 10 µM. Since these color changes were similarly perceived in tap and lake water samples, the present method could be a promising candidate for simple, cost-effective visual monitoring of copper onsite.publishersversionpublishe

Selective Coordination of Cu2+ and Subsequent Anion Detection Based on a Naphthalimide-Triazine-(DPA)2 Chemosensor

UIDB/50006/2020 SFRH/BD/120985/2016 Project LISBOA-01-0145-FEDER-007660 PPBI-POCI-01-0145-FEDER-022122 DL 57-021/DL/2018 ROTEIRO/0031/2013-PINFRA/22161/2016A new fluorescent chemosensor for copper (II) and subsequent anion sensing was designed and fully characterized. The sensor consisted of a 1,8-naphthalimide core, bearing two terminal dipicolylamine (DPA) receptor units for binding metal cations, and an ethoxyethanol moiety for enhanced water solubility. The DPA units are connected to position 4 of the fluorophore via a triazine-ethylenediamine spacer. Fluorescence titration studies of the chemosensor revealed a high selectivity for Cu2+ over other divalent ions, the emissions were strongly quenched upon binding, and a stability constant of 5.52 log units was obtained. Given the distance from DPA chelating units and the fluorophore, quenching from the Cu2+ complexation suggests an electron transfer or an electronic energy transfer mechanism. Furthermore, the Cu2+-sensor complex proved to be capable of sensing anionic phosphate derivatives through the displacement of the Cu2+ cation, which translated into a full recovery of the luminescence from the naphthalimide. Super-resolution fluorescence microscopy studies performed in HeLa cells showed there was a high intracellular uptake of the chemosensor. Incubation in Cu2+ spiked media revealed a strong fluorescent signal from mitochondria and cell membranes, which is consistent with a high concentration of ATP at these intracellular sites.publishersversionpublishe

Toward Light-Controlled Supramolecular Peptide Dimerization

The selective photodeprotection of the NVoc-modified FGG tripeptide yields the transformation of its 1:1 receptor−ligand complex with cucurbit[8]uril into a homoternary FGG2@CB8 assembly. The resulting lightinduced dimerization of the model peptide provides a tool for the implementation of stimuli-responsive supramolecular chemistry in biologically relevant contexts.The work was supported by the Associate Laboratory for Green ChemistryLAQV (UIDB/50006/2020) and by the Applied Molecular Biosciences UnitUCIBIO (UIDB/ 04378/2020), both financed by FCT. FCT/MCTES is also acknowledged for supporting the National Portuguese NMR Network (ROTEIRO/0031/2013-PINFRA/22161/2016, cofinanced by FEDER through COMPETE 2020, POCI, PORL, and FCT through PIDDAC) and for the grants PTDC/QUICOL/32351/2017, PTDC/QUI-QFI/30951/2017, and CEECIND/00466/2017 (N.B.). U.P. thanks the Spanish Ministry of Science, Innovation, and Universities (CTQ2017-89832-P). We are grateful to Dr. J.P. Da Silva for the mass spectrometry data (equipment financed by CRESC Algarve 2020 and COMPETE 2020; project EMBRC.PT ALG-01-0145-FEDER022121). Funding for open access charge: Universidad de Huelva / CBU

Supramolecular tripodal Au(I) assemblies in water. Interactions with pyrene fluorescent probe

The synthesis of three gold(I) tripodal complexes derived from tripropargylamine and containing the water soluble phosphines PTA (1, 3,5-triaza-7-phosphaadamantane), DAPTA (3,7-diacetyl-1,3,7-triaza--phosphabicyclo[3.3.1]nonane) and TPPTS (triphenylphosfine-3,3',3''-trisulfonic acid trisodium salt) is here described. The three complexes are observed to give rise to the formation of supramolecular aggregates in water and very long fibers. This property has been analyzed by means of 1H-NMR spectroscopy at different concentrations and SAXS. The results point out the important role of the phosphine moieties as the main enthalpic or entropic contribution in the resulting Gibbs energy of aggregates formation. The tripodal structure of the three complexes together with the presence of gold(I) atoms make them ideal candidates to interact with hydrophobic molecules also in water. For this, the interaction with pyrene in this solvent has been evaluated with successful results in all three complexes. The highest association constant corresponds to 2 as the host. DFT studies indicates the location of pyrene in the tripodal cavity as the most stable conformation. The interaction with pyrene has been additionally studied within cholate hydrogel matrixes pointing out the stability of the resulting host:guest adducts in the different medium

A coumarin based gold(I)-alkynyl complex: a new Q1 class of supramolecular hydrogelators

A phosphine-gold(I)-alkynyl-coumarin complex, [Au{7-(prop-2-ine-1-yloxy)-1-benzopyran-2-one}-(DAPTA)] (1), was synthesized and the formation of long luminescent fibers in solution was characterized via fluorescence microscopy and dynamic light scattering. The fibers presented strong blue and green luminescence, suggesting that the gold(I) in the complex increased intersystem crossing due to the heavy atom effect, resulting in a significant increase in triplet emission. The X-ray structure of the fibers indicates that both aurophilic, π-π interactions and hydrogen bonding contribute to their formation in aqueous solvents

Aggregation induced emission of a new naphthyridine-ethynyl-gold(I) complex as a potential tool for sensing guanosine nucleotides in aqueous media

A new organometallic alkynyl-gold(I) complex, capable of exhibiting Aggregation Induced Emission was designed and synthesized. The linear complex structure possesses a central Au(I) atom, bearing two axial ligands: (1) 1,3,5-Triaza-7-phosphaadamantane; and (2) 2- acetamido-7-ethynyl-1,8-naphthyridine. While the former accounts for its partial solubility in aqueous environment, the latter acts as a receptor unit for binding guanosine nucleotides and derivatives via multiple hydrogen bonding. At high concentrations, aggregation of the complex was observed by the formation of new absorption (λmax ~ 400 nm) and emission bands (550-700 nm). Formation of aggregates of ca. 60 nm diameter was confirmed with Small Angle X-Ray Scattering (SAXS). Disruption of the aggregates in the presence of guanosine derivatives resulted in a ratiometric signal with apparent association constants in the order of 105 M-1 and high sensitivity (around 63% signal change) which are, to the best of our knowledge, in line with the highest recorded for nucleotide sensing based on hydrogen bonding that are capable of working in water. Computational studies indicate the presence of additional hydrogen bonding interactions that account for the strong binding of the Au(I) complex to phosphorylated Guanosine nucleotides

Non-emissive RuII Polypyridyl Complexes as Efficient and Selective Photosensitizers for the Photooxidation of Benzylamines

RTI2018-100709-B-C21 CTQ (QMC)-RED2018-102471-T) Junta de Castilla y Leon (BU087G19 FEDER (BU042U16-BU305P18).Five new RuII polypyridyl complexes bearing N-(arylsulfonyl)-8-amidoquinolate ligands and three of their biscyclometalated IrIII congeners have been prepared and employed as photocatalysts (PCs) in the photooxidation of benzylamines with O2. In particular, the new RuII complexes do not exhibit photoluminescence, rather they harvest visible light efficiently and are very stable in solution under irradiation with blue light. Their non-emissive behavior has been related to the low electrochemical energy gaps and rationalized on the basis of theoretical calculations (DFT analysis) that predict low S0←T1 energy values. Moreover, the RuII complexes, despite being non-emissive, display excellent activities in the selective photocatalytic transformation of benzylamines into the corresponding imines. The presence of an electron-withdrawing group (-CF3) on the arene ring of the N-(arylsulfonyl)-8-amidoquinolate ligand improves the photocatalytic activity of the corresponding photocatalyst. Furthermore, all the experimental evidence, including transient absorption spectroscopy measurements suggest that singlet oxygen is the actual oxidant. The IrIII analogues are considerably more photosensitive and consequently less efficient photosensitizers (PSs).authorsversionpublishe