Detection of nitroaromatic explosives by new D–π–A sensing fluorophores on the basis of the pyrimidine scaffold

Abstract

A series of D-π-A- type dyes based on pyrimidines, bearing various thiophene linkers, have been studied as sensing fluorophores. Fluorescence studies have demonstrated that the emission of all derivatives is sensitive to the presence of nitroaromatic explosives, such as 2,4,6-trinitrophenol (PA), 2,4,6-trinitrotoluene (TNT), and 2,4-dinitrotoluene (DNT), in their acetonitrile solutions. The detection limits of fluorophores to PA, TNT, and DNT proved to be in the range from 5.83 × 10(-6) to 2.38 × 10(-7) mol/L, 1.70 × 10(-4) to 8.40 × 10(-6) mol/L, and 8.39 × 10(-5) to 6.87 × 10(-6) mol/L, respectively. The theoretical investigation into the quenching mechanism in the presence of fluorophore has been performed. All compounds have shown a good efficiency as sensor materials when tested as elements of the original device «Nitroscan» for detecting nitro-containing explosives in vapor phase (Plant "Promautomatika", Ekaterinburg, Russia). Graphical Abstract ᅟ.

New "turn-off" fluorescence sensors to detect vapors of nitro-explosives on the basis of 4,6-bis[5-(heteroaryl)thiophen-2-yl] substituted 5-(4-tert-butylphenyl)pyrimidines

“…In our opinion, the most reasonable explanation of this fact is a steric hindrances increase with an addition of substituents in benzene ring. The linear relationship for the Stern-Volmer plot (in the range of concentrations from 0 to 2×10 -6 M) (Figures S6 and S7 in Supporting Information) and similarity of structures with linear and V-shaped push-pull pyrimidines, 35,40 bearing triphenylamine and carbazole as electron-donating fragment, suggests a high role of static type interactions for the quenching process.…”

“…Such structures have been used as promising sensing materials for detection of a variety of nitroaromatics through fluorescence quenching. [33][34][35][36][37][38][39][40] As a part of our research studies on pyrimidine-based π-conjugated systems, we envisaged that mixed π-conjugated 4,6-bis[5-(heteroaryl)-thiophen-2-yl]-5-(4-tert-butylphenyl) pyrimidines, consisting of the electrondonating part, presented by triphenylamine, carbazole or pyrene fragments, and the electron-withdrawing pyrimidine unit, would be a new class of push-pull fluorophores with improved sensitivity towards nitroaromatic compounds. Indeed, we have been motivated to synthesize D-π-A-π-D conjugates 7a-c, in which electrondonating groups are attached to 4-and 6-positions of the pyrimidine ring via the thiophene spacer and 4-tertbutylphenyl substituent is incorporated at C-5 of pyrimidines.…”

Electron‐Withdrawing Substituted Quinazoline Push‐Pull Chromophores: Synthesis, Electrochemical, Photophysical and Second‐Order Nonlinear Optical Properties

“…The pyrimidinyl (1,3‐diazinyl) fragment has been widely used as electron‐deficient part in push‐pull structures . The luminescence properties of pyrimidine fluorophores are highly sensible to external stimuli and have been used as sensors of polarity, pH,[14b], [14c] metal cations and nitrogen explosives . Push‐pull pyrimidine derivatives are also well‐known for their TPA properties .…”

The Solvatofluorochromism of 2,4,6‐Triarylpyrimidine Derivatives

“…By varying the pyrimidine acceptor group A, the conjugating linkage π , or the donor group D, the solvatofluorochromic properties of these dyes can be widely varied. Examples of such variations include the direct linking between a pyrimidine ring and an amino group , conjugation of a pyridimidine system with a methoxyphenyl group , with an aminophenyl group linked through an ethylene bridge or through an arylene , or heteroarylene spacer .…”