Design and Development of Fluorescent Sensors with Mixed Aromatic Bicyclic Fused Rings and Pyridyl Groups: Solid Mediated Selective Detection of 2,4,6-Trinitrophenol in Water.

ABSTRACT: For a strategic incorporation of both ?-electron-rich moieties and Lewis basic moieties acting as hydrogen bonding recognition sites in the same molecule, two new fluorescent sensors, N,N'-bis(anthracen-9-ylmethyl)-N,N'-bis(pyridin-2-ylmethyl)butane-1,4-diamine (banthbpbn, 1) and N,N'-bis(naphthalen-1-ylmethyl)-N,N'-bis(pyridin-2-ylmethyl)butane-1,4-diamine (bnaphbpbn, 2), have been developed for the selective detection of highly explosive 2,4,6-trinitrophenol (TNP) in water. Each of the two identical ends of these sensors that are linked with a flexible tetra-methylene spacer contains a mixed aromatic bicyclic fused ring (anthracene or naphthalene) and a pyridyl group. These are synthesized via the simple reduced Schiff base chemistry, followed by the nucleophilic substitution reaction under basic conditions in high yields. Both 1 and 2 were characterized by Fourier transform infrared, UV-vis, and NMR (¹H and ¹³C) spectroscopy, and high-resolution mass spectrometry. The bulk phase purity of 1 and 2 and their stability in water were confirmed by powder X-ray diffraction (PXRD). Utilizing the effect of solvents on their emission spectra as determined by fluorescence spectroscopy, spectral responses for 1 and 2 toward various nitro explosives were recorded to determine a detection limit of 0.6 and 1.6 ppm, respectively, for TNP in water via the "turn-off" quenching response. Also, the detailed mechanistic investigation for their mode of action through spectral overlap, lifetime measurements, Stern-Volmer plots, and density functional theory calculations reveals that resonance energy transfer and photoinduced electron transfer processes, and electrostatic interactions are the key aspects for the turn-off response toward TNP by 1 and 2. In addition, the selectivity for TNP has been found to be more in 1 compared to 2. Both exhibit good recyclability and stability after sensing experiments, which is confirmed by PXRD and field-emission scanning electron microscopy.

SUBMITTER: Chakraborty G 

PROVIDER: S-EPMC6641284 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature