Benzo[de]naphtho[1,8-gh]quinolines: synthesis, photophysical studies and nitro explosives detection

A rational synthetic approach to substituted naphtho[1,8-gh]quinolines using intramolecular cyclization in the presence of potassium in the series of (naphthalen-1-yl)isoquinolines is described. The photophysical properties of the obtained compounds were studied; in particular, fluorescence emission was detected in the range 454 - 482 nm with a quantum yield of up to 54%. We also calculated the HOMO-LUMO energies and optimized molecular structures for the resulting fluorophores. Based on the results of fluorescence titration, the Stern-Volmer constants (up to 21587 M-1) and the detection limits of nitroanalytes (up to 1.4 ppm) were calculated, confirming the possibility of their use as potential chemosensors for the visual detection of nitro-containing explosives

New naphtho[1,8-ef]perimidines: synthesis, fluorescence studies and application for detection of nitroanalytes

A rational approach to the synthesis of substituted naphtho[1,8-ef]perimidines based on SNH methodology and cyclization  reaction in the series of condensed azines with naphthalene substituents was presented. Photophysical properties of the obtained fluorophores were studied, in particular, green fluorescence in the 485–536 nm range with quantum yield up to 32.4% was detected. HOMO-LUMO energy values and distributions for the new compounds were calculated by the DFT method in comparison with nitroanalytes and perylene. Based on the data obtained, as well as on the results of fluorescence titration, the possibility of using the new diazaperylenes as potential chemosensors for the visual detection of nitro-containing explosives was shown

Conjugates of 8-[2,2’-bipyridinyl]coumarins as potential chemosensors for Al3+, Cu2+, Cd2+, Zn2+ ions: synthesis and photophysical properties

In this work, we report the synthesis of novel coumarin-bipyridine conjugates using a sequence of C–C coupling reaction between 5,7-dimethoxycoumarins and 3-pyridyl-6-aryl-1,2,4-triazines followed by the Boger reaction with norbornandiene to obtain 8-[2,2'-bipyridyl]-5,7-dimethoxycoumarins. Photophysical properties were investigated for the obtained series of 8-[2,2'-bipyridyl]-5,7-dimethoxycoumarins: absorption and emission wavelength maxima are in the region of 212–296 and 401–410 nm, respectively; Stokes shifts are up to 116 nm, and fluorescence quantum yields are up to 15.0%. It was found that titrating the conjugates with Al3+, Zn2+, and Cd2+ ions results in an increase in the intensity of the emission maxima of the complexes, while the opposite effect was observed in the case of titration with Cu2+ ions. These findings suggest that the studied compounds may be considered as promising chemosensing materials. Finally, a positive solvatochromism of 8-[2,2'-bipyridyl]coumarins and their metal complexes was established. The experimental data are supported by mathematical calculations according to the Lippert-Mataga equation and Kosower diagram

New 2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-2,2’-bipyridine-based co-polymer, synthesis, photophysical properties and response to metal cations

A new co-polymer based on fragments of 2-(2-pyridyl)monoazatriphenylene and 2,5-bis (2-ethylhexyl)-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione was prepared by using the Sonogashira reaction. The photophysical properties of the polymer were studied. The presence of a strong bathochromic shift of the absorption and emission maxima in comparison with the previously described monomer units is shown. The polymer exhibits an intense “turn-off” response toward Cu2+ cations

(Mechano)synthesis of azomethine- and terpyridine-linked diketopyrrolopyrrole-based polymers

Three efficient synthetic approaches towards new azomethine- and terpyridine-containing 2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (diketopyrrolopyrrole, DPP) based polymers, such as P1 and P2, are reported. The first approach involves the Pd-catalyzed synthesis via two- or three-component Suzuki or Stille cross-coupling reaction in solution. The second approach involves Pd-catalyzed Suzuki cross-coupling reaction under ball-milling conditions. And, finally, the third approach involves Pd-free condensation reaction under ball-milling conditions. The newly obtained polymers exhibited absorbance around 700 nm and emission around 900 nm, and, thus, these polymers are considered to be NIR-fluorophores

Mechanosynthesis of Diaminobiphenyls-Based Schiff’s Bases as Simple Probes for the Naked-Eye Detection of Cyanide Ion

Cyanide ions are known to be lethal for insects and mammals and harmful for the environment, and new methods for their selective detection are in high demand. Herein, the mechanosynthesis of simple Schiff’s bases-based probes S1–S3 for visual detection of CN− anion is reported. These probes were obtained by means of a reaction between isomeric 4,4-, 3,3- and 2,2-diaminobiphenyls and 4-nitrobenzaldehyde under ball milling conditions. The probes showed high selectivity and sensitivity toward CN− anion via a dramatic “yellow-to-dark purple” color change with a detection limit of 26 × 103, 8.7 × 103 and 14 × 103 ppm for S1–S3, respectively. The proposed mechanism of the detection suggests the deprotonation of a proton from an imine moiety, followed by the formation of charge transfer complexes (CTC)

Fluorescent Pyranoindole Congeners: Synthesis and Photophysical Properties of Pyrano[3,2-<i>f</i>], [2,3-<i>g</i>], [2,3-<i>f</i>], and [2,3-<i>e</i>]Indoles

This paper reports the synthesis of four types of annulated pyranoindole congeners: pyrano[3,2-f]indole, pyrano[2,3-g]indole, pyrano[2,3-f]indole, and pyrano[2,3-e]indole and photophysical studies in this series. The synthesis of pyrano[3,2-f], [2,3-g], and [2,3-e]indoles involve a tandem of Bischler–Möhlau reaction of 3-aminophenol with benzoin to form 6-hydroxy- or 4-hydroxyindole followed by Pechmann condensation of these hydroxyindoles with β-ketoesters. Pyrano[2,3-f]indoles were synthesized through the Nenitzescu reaction of p-benzoquinone and ethyl aminocrotonates and subsequent Pechmann condensation of the obtained 5-hydroxyindole derivatives. Among the pyranoindoles studied, the most promising were pyrano[3,2-f] and [2,3-g]indoles. These compounds were characterized by moderate to high quantum yields (30–89%) and a large (9000–15,000 cm−1) Stokes shift. More detailed photophysical studies were carried out for a series of the most promising derivatives of pyrano[3,2-f] and [2,3-g]indoles to demonstrate their positive solvatochromism, and the data collected was analyzed using Lippert-Mataga equation. Quantum chemical calculations were performed to deepen the knowledge of the absorption and emission properties of pyrano[3,2-f] and [2,3-g]indoles as well as to explain their unusual geometries and electronic structures

Synthesis and Photophysical Properties of α-(<i>N</i>-Biphenyl)-Substituted 2,2′-Bipyridine-Based Push–Pull Fluorophores

A series of new α-(N-biphenyl)-substituted 2,2′-bipyridines were obtained through the combination of the ipso-nucleophilic aromatic substitution of the C5-cyano group, aza-Diels–Alder and Suzuki cross-coupling reactions, starting from 5-cyano-1,2,4-triazines. For the obtained compounds, photophysical and fluorosolvatochromic properties were studied. Fluorophores 3l and 3b demonstrated unexpected AIEE activity, while 3a and 3h showed promising nitroexplosive detection abilities