Simple Bisthiocarbonohydrazone as a Sensitive, Selective, Colorimetric, and Ratiometric Fluorescent Chemosensor for Picric Acids (original) (raw)
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ChemistrySelect, 2019
Rhodamine dye containing Isonicotinic hydrazide (RBN-1) is synthesized for the sensing of nitro aromatics, the probe showed turn-on fluorescence with Picric acid in coexistence with other interfering nitro aromatics. The sensor RBN-1 can be used for naked eye detection of picric acid with the detection limit of 37.3 nM in solution. The RBN-1 + PA complexation involves intermolecular hydrogen bonding between the pyridine N and the hydroxyl group of PA. The observed photophysical changes of RBN-1 with Picric acid is attributed to the spirolactam ring opening. The effective sensing ability of RBN-1 is tested in real water samples and paper strip experiments, the results are in good agreement with the pilot analysis.
Supramolecular control over recognition and efficient detection of picric acid
Chem. Commun., 2014
Bimetallic Schiff-base Al 3+ complexes bearing ester functions at the periphery of the ligands are shown to be efficient fluorescent chemosensors for picric acid detection. The prominent role of an association between the chemosensor and the picric acid in the detection process is demonstrated. The detection of picric acid in water is achieved with the sensor deposited on paper. † Electronic supplementary information (ESI) available: Synthesis and characterization of 1, 2, 3 and 1.PA; X-ray diffraction data collection and refinement; procedures for spectroscopic measurements by emission and NMR; procedures for theoretical calculations. CCDC 981331-981333. See
Chemistry (Weinheim an der Bergstrasse, Germany), 2016
2,6-Divinylpyridine-appended anthracene derivatives flanked by two alkyl chains at the 9,10-position of the core have been designed, synthesized, and characterized by NMR, MALDI-TOF, FTIR, and single-crystal XRD. These anthracene derivatives are able to recognize picric acid (2,4,6-trinitrophenol, PA) selectively down to parts per billion (ppb) level in aqueous as well as nonaqueous medium. Fluorescence emission of these derivatives in solution is significantly quenched by adding trace amounts of PA, even in the presence of other competing analogues, such as 2,4-dinitrophenol (2,4-DNP), 4-nitrophenol (NP), nitrobenzene (NB), benzoic acid (BA), and phenol (PH). The high sensitivity of these derivatives toward PA is considered as a combined effect of the proton-induced intramolecular charge transfer (ICT) as well as electron transfer from the electron-rich anthracene to the electron-deficient PA. Moreover, visual detection of PA has been successfully demonstrated in the solid state by...
ACS Omega
A hydrazone-based N ′ 1 , N ′ 3-b i s ((E)-4-(diethylamino)-2 − hydroxybenzylidene)isophthalohydrazide (NDHIPH), has been synthesized, characterized, and assessed for its highly selective and sensitive (limit of detection, 2.53 nM) response toward Al(III) via fluorescence enhancement in 95% aqueous medium. All experimental results of analytical studies are in good consonance with the theoretical studies performed. Further, this NDHIPH-Al(III) ensemble is used for selective and sensitive (12.15 nM) detection of explosive picric acid (PA) via fluorescence quenching. This reversible behavior of NDHIPH toward Al(III) and PA is used for the creation of a molecular logic gate.
Efficient Discovery of Fluorescent Chemosensors Based on a Biarylpyridine Scaffold
Organic Letters, 2010
Fluorescent chemosensors for ions and neutral molecules have been a subject of numerous research publications and review articles over the last decades.1 Relatively recently a new fluorescent signaling mechanism, binding induced conformational restriction, was discovered. In the first part of this dissertation a library of 10 potential fluorescent chemosensors with chelating groups known to have high affinity for cations and anions is presented. All are based on the biarylpyridine scaffold appended with two identical receptor arms. The previous synthesis of the biaylpyridine core fluorophore was improved with significant reduction of the number of steps and increase in the overall yield. This made the core fluorophore more accessible. Three fluoroionophores capable of sensing Hg(II) and Ag(I) ions in aqueous solution were identified. As binding domains phenylthiourea (with (Gly-Thio) and without (Thio) glycine as a linker between the binding site and a signaling subunit) and dithioazacrown (Crown) were used. Despite high affinity for Hg(II) and Ag(I) in case of Thio and Crown chemosensors, both fail to distinguish between the two ions when they are contained in one sample. Gly-Thio chemosensor suggests the possibility of discriminating Hg(II) and Ag(I) due to significant (80 nm) blue shift upon addition of Hg(II) accompanied by an increase in emission intensity. Ratiometric detection of this type (with single-fluorophore) is comparatively rare and provides more accurate and quantitative measurements of metal ion concentration. Computational study of simple analogues of the Hg-complexes of the fluorescent chemosensors identified from the library showed high steric congestion of complexes, which may prevent cooperative ion binding in some cases. This result explains why the majority of library members are not effective chemosensors and makes it possible to predict structural changes of the binding site necessary to design next-generation chemosensors with improved properties. The second part of the dissertation reports a fluorescence assay for the visual detection of the common terrorist explosive triacetone triperoxide (TATP). Our fluorescent probe for TATP relies on the sulfoxide/sulfone redox couple attached to a Literature references are listed on p. 28 (Chapter 1). fluorophore (pyrene). In this couple the sulfone is much more fluorescent than the corresponding sulfoxide. In the presence of a catalyst (methyltrioxorhenium) sulfoxides react rapidly with H2O2 generated by UV irradiation of TATP. Oxidation of the sulfoxide to sulfone leads to ca. 50-fold fluorescence increase, which can be seen with naked eye. This fluorescence assay is capable of detecting as little as 100 nmol of TATP. Further development of sulfur based fluorescent chemosensors and use of longer wavelength fluorophore makes it essential to understand the photophysical origin of low sulfoxide emission relative to sulfones. A combined experimental and computational approach has been taken. Several sulfide/sulfoxide/sulfone series differing in the number of carbon atoms between sulfur and the fluorophore (pyrene) as well as substituents (alkyl or aryl) attached to the sulfur atom were prepared. Our initial assumption, photoinduced electron transfer as a fluorescence quenching mechanism, was rejected on the basis of distance (the number of carbon atoms) independency between the fluorophore and the sulfur atom. Results from photolysis experiments have established that the excited state of aryl sulfoxides is quenched by reversible radical formation/recombination (so-called-cleavage). For an efficient quenching of fluorescence the presence of an S-Ar fragment is required. Computational study has identified a low lying excited state (S2) of the sulfoxide in which the S-Ar fragment is electronically coupled to the excited pyrene chromophore and the excited state energy is transferred to the S-Ar, leading to C-S bond cleavage. The subsequent radical recombination in the solvent cage leads to sulfoxide reformation. Excitation energy is consumed and fluorescence quenching is observed. These studies provide the basis for designing TATP-responsive fluorescent probes with longer emission wavelength. Zusammenfassung Fluoreszierende Chemosensoren für Ionen und neutrale Moleküle waren Thema zahlreicher Forschungspublikationen und Übersichtsartikel in den letzten Jahrzehnten. Vor kurzem wurde ein neuer Mechanismus zur Anregung der Fluoreszenz entdeckt, der auf Konformationsrestriktion beruht, die durch die Bindung eines Substrates an den Sensor verursacht wird. Im ersten Teil dieser Dissertation wird eine Bibliothek aus zehn potentiell fluoreszierenden Chemosensoren vorgelegt. Die Zielverbindungen sind mit chelierenden Rezeptorgruppenruppen ausgestattet, die für ihre hohe Affinität zu Kationen und Anionen bekannt sind. Alle Verbindungen beruhen auf einem Biarylpyridin-Gerüst mit zwei identischen Rezeptorgruppen. Der bisherige Syntheseweg zum Biarylpyridin Kern-Fluorophor wurde erheblich verbessert, indem die Zahl der Syntheseschritte verringert wurde. Die Verbesserung der Gesamtausbeute machte den Kern-Fluorophor somit zugänglicher. Drei Fluoroionophore wurden gefunden, die in der Lage sind Hg(II)-und Ag(I)-Ionen in wässriger Lösung nachzuweisen. Phenylthioharnstoff (mit Glycin (Gly-Thio) und ohne Glycin (Thio) als Linker Zwischen der Bindungsstelle und dem fluoreszierenden Teil des Sensors) und Dithioaza-Kronenether (Crown) wurden als Bindungseinheiten verwendet. Trotz der hohen Affinität von Thio und Crown zu Hg(II) und Ag(I), konnte in einer Probe nicht zwischen diesen Ionen unterschieden werden. Gly-Thio bietet jedoch die Möglichkeit zwischen Hg(II) und Ag(I) zu unterscheiden, da die Bindung von Hg(II) zu einer erheblichen Blauverschiebung (80nm) und einem Anstieg der Emissionsintensität führt. Dadurch können durch Ratiometrische Fluoreszenz-Messungen, vergleichsweise selten mit einzelnen Fluorophoren, Konzentrationen von Metall-Ionen genau bestimmt werden. Rechnergestützte Strukturanalysen einfacher Analogverbindungen der fluoreszierenden Chemosensoren aus der Bibliothek zeigten hohe sterische Überlastung im Falle der Hg-Komplexe. In manchen Fällen kann dadurch kooperative Ionen-Bindung verhindert werden. Dieses Ergebnis erklärt, weshalb die Mehrheit der synthetisierten Moleküle keine effektiven Chemosensoren darstellen. Weiterhin können strukturelle Veränderungen vorhergesagt werden, die nötig sind, um die nächste Generation von Chemosensoren mit verbesserten Eigenschaften zu entwickeln. Im zweiten Teil der Arbeit wird eine Methode zur Detektion des Sprengstoffs Triacetontriperoxid (TATP) vorgestellt, der häufig von Teroristen verwendet wird. Unsere Fluorophore beruhen auf Sulfoxid/Sulfon Redox-Paaren, welche an Pyren gebunden sind, wobei das jeweilige Sulfon generell intensiver fluoresziert als das Sulfoxid. In Anwesenheit des Katalysators Methyltrioxorhenium reagieren Sulfoxide schnell mit dem durch UV-Bestrahlung von TATP erzeugten Wasserstoffperoxid. Dabei wird eine 50-fache Erhöhung der Fluoreszenz bobachtet, die mit blossem Auge zu sehen ist. Mit der vorgestellten Fluoreszenzanalyse ist der Nachweis von weniger als 100 nmol TATP möglich. Für weitere Entwicklungen Schwefel basierter Fluoreszenz-Sensoren ist es entscheidend, die photophysikalischen Grundlagen der geringeren Emission von Sulfoxiden relativ zu Sulfonen zu verstehen. Ein experimenteller und rechnergestützter Ansatz wurde zu diesem Zweck gewählt. Homologe Reihen von Sulfiden/Sulfoxiden/Sulfonen mit unterschiedlicher Anzahl von Kohlenstoffatomen zwischen dem Schwefelatom und dem Fluorophor (Pyren) sowie mit verschiedenen Substituenten (Alkyl or Aryl) wurden hergestellt. Die ursprüngliche Annahme, Fluoreszenzlöschung beruhe auf photoinduziertem Elektronentransfer, wurde aufgrund der fehlenden Korrelation zwischen Fluoreszenzlöschung und Abstand Schwefelatom-Fluorophor abgelehnt. Photolytische Experimente mit Sulfoxiden ergaben, dass der angeregte Zustand von Sulfoxiden durch reversible Radikalbildung und Rekombination (a-Spaltung) gelöscht wird. Für eine effiziente Löschung der Fluoreszenz ist die Anwesenheit eines S-Ar-Fragmentes unabdingbar. Berechnungen ergaben einen tief liegenden angeregten Zustand (S2) der Sulfoxide. In diesem Zustand ist das S-Ar Fragment mit dem angeregten Pyren elektronisch gekoppelt, was die Übertragung der Anregungsenergie vom Pyren auf den S-Ar Teil ermöglicht. Dies führt zur Spaltung der C-S Bindung und anschließender Rekombination der Radikale zum ursprünglichen Sulfoxid. Dadurch wird die Anregungsenergie verbraucht und Fluoreszenzlöschung wird beobachtet. Diese Untersuchungen bilden die Grundlage zur Synthese fluoreszierender Chemosensoren für TATP die bei größeren Wellenlängen absorbieren und emittieren.
Organic Letters, 2002
The 1,3-diphenyl-1H-pyrazolo[3,4-b]-quinoline chromophore is a versatile building block for the construction of brightly fluorescent molecular sensors. Facile synthetic procedures allow integration of the chromophore into fluorophore−spacer−receptor systems as well as fluoroionophores operating via intramolecular charge transfer. Whereas the former photoinduced electron-transfer probes show strong analyte-induced fluorescence enhancement, the latter exhibit bright ratiometric dual emission. Employing prototype macrocyclic receptors, the favorable signaling features for metal ion recognition are demonstrated. Research efforts in the field of molecular sensors indicating chemical stimuli or environmental parameters by a change in their fluorescence properties are still very intensive. 1 In the past few years, besides striving to improve the selectivity of such compounds by advancing the recognition unit, several new directions have been followed to improve their sensitivity. 2 Within the field of fluorescent molecular probe research, modular approaches are especially appealing. 3,4 In an ideal case, such strategies allow compounds to be tailor-made for certain wavelength ranges, analytes, or sensing media by assembling functional units with desired properties from a pool of precursors. Thus, for a successful design, the