calix(4)arene and benzimidazole

A new benzimidazole-functionalized calix[4]arene receptor (R) was synthesized and characterized. The receptor R shows better selectivity toward trinitrotoluene (TNT) compared to the other nitro explosives in solution, which also retains its effectiveness for solid-phase detection. The chemical interactions of the molecule with different nitro explosive analytes were studied by fluorescence spectroscopy and by a molecular dynamics approach. The molecular dynamics studies show a 1:3 complex between R and TNT, and hence high sensitivity was imparted by fluorescence studies. The detection of explosive vapors in ambient conditions was tested by using a sensitive coating layer of R on an SU-8/CB-based piezoresistive cantilever surface. The developed device showed large sensitivity toward TNT compared to cyclotrimethylenetrinitramine (RDX) and pentaerythritol tetranitrate (PETN) in the solid state at their respective vapor pressures at room temperature. The detection sensitivity of the device was estimated to be 35 mV for TNT at ambient conditions. Moreover, the sensor does not show a response when exposed to humidity. These results demonstrate that R can be used as one of the coating materials for a cantilever for the detection of TNT using piezoresistivity measurement. R can also detect the explosives in solution with high sensitivity and selectivity by fluorescence spectroscopy.

Topics: Benzimidazoles; Calixarenes; Epoxy Compounds; Explosive Agents; Molecular Dynamics Simulation; Nanostructures; Phenols; Polymers; Spectrometry, Fluorescence; Surface Properties; Temperature; Trinitrotoluene

A benzimidazole appended triazole linked 1,3-diconjugate of calix[4]arene (L) has been synthesized and characterized. The conjugate L has been found to recognize Cu(2+) among the thirteen different metal ions studied by exhibiting ratiometric fluorescence changes through newly generated excimer band at ∼380 nm. Fluorescence off-on-off behavior has been clearly demonstrated on the basis of the binding variability of Cu(2+) to L. The binding has been elicited through the changes observed in the fluorescence, ESI MS and (1)H NMR titrations. All the other metal ions studied do not show any new band and further do not interfere with the recognition of Cu(2+) by L, even when these are present in the same medium. The structural features of both the mono- and di-nuclear complexes were established by DFT computational calculations and found to display highly distorted geometry about the copper centers that deviate from both the tetrahedral and the square planar.

Topics: Benzimidazoles; Buffers; Calixarenes; Copper; Crystallography, X-Ray; Ions; Molecular Conformation; Phenols; Spectrometry, Fluorescence; Triazoles