karthik rajendran - Electron rich supramolecular polymers as fluorescent sensors for nitroaromatics

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  Shanmugaraju, Sankarasekaran, Jadhav, Harshal, Karthik,   Rajendran, Mukherjee, Partha Sarathi, Singh, Suryabhan, Karthik,   Rajendran RSC Advances 2013 3  (15) 4940-4950

  Abstract: Three [small pi]-electron rich   fluorescent supramolecular polymers (1-3) have been synthesized   incorporating 2-methyl-3-butyn-2-ol groups in reasonable yield by   employing Sonagashira coupling. They were characterized by   multinuclear NMR (1H, 13C), ESI-MS and single crystal X-ray   diffraction analyses [1 = 1-(2-methyl-3-butyn-2-ol)pyrene; 2 =   9,10-bis(2-methyl-3-butyn-2-ol)anthracene; 3 =   1,3,6,8-tetrakis(2-methyl-3-butyn-2-ol)pyrene]. Single crystal   structures of 1-3 indicated that the incorporation of hydroxy   (-OH) groups on the peripheral of the fluorophores helps them to   self-associate into an infinite supramolecular polymeric network   via intermolecular hydrogen bonding interactions between the   adjacent discrete fluorophore units. All these compounds showed   fluorescence characteristics in chloroform solution due to the   extended [small pi]-conjugation and were used as selective   fluorescent sensors for the detection of electron deficient   nitroaromatics. The changes in photophysical properties of   fluorophores (1-3) upon complex formation with electron deficient   nitroaromatic explosives were studied in chloroform solution by   using fluorescence spectroscopy. All these fluorophores showed   the largest quenching response with moderate selectivity for   nitroaromatics over various other electron deficient/rich   aromatic compounds tested (Chart 1). Analysis of the fluorescence   titration profile of 9,10-bis(2-methyl-3-butyn-2-ol)anthracene   fluorophore (2) with 1,3,5-trinitrotoluene/2,4-dinitrotoluene   provided evidence that this particular fluorophore detects   nitroaromatics in the nanomolar range [2.0 ppb for TNT, 13.7 ppb   for DNT]. Moreover, sharp visual color change was observed upon   mixing nitroaromatic (DNT) with fluorophores (1-3) both in   solution as well as in solid phase. Furthermore, the vapor-phase   sensing study of thin film of fluorophores (1-3) showed efficient   quenching responses for DNT and this sensing process is   reproducible. Selective fluorescence quenching response including   a sharp visual color change for nitroaromatics make these tested   fluorophores (1-3) as potential sensors for nitroaromatic   compounds with a detection limit of ppb level.

  Address (URL): http://dx.doi.org/10.1039/C3RA23269G