Browsing by Author "Santra, Sougata"

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    Extended cavity pyrene-based iptycenes for the turn-off fluorescence detection of RDX and common nitroaromatic explosives†‡
    (RSC Publishing, 2017) Khasanov, Albert F.; Kopchuk, Dmitry S.; Kovalev, Igor S.; Taniya, Olga S.; Giri,Kousik; Slepukhin, Pavel A.; Santra, Sougata; Rahman, Matiur; Majee, Adinath; Charushin, Valery N.; Chupakhin, Oleg N.
    Extended cavity pyrene-based iptycenes have been synthesized by using the Diels–Alder reaction between in situ generated dehydropyrenes and anthracene. The photophysical properties and the interaction of these iptycenes with nitro-explosive components were studied both in solution and in the solid state by using fluorescence spectroscopy and X-ray crystallography, respectively. Due to the presence of both the large iptycene cavity and the central pyrene core, an unprecedently high fluorescence-quenching response towards non-aromatic and non-planar 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) has been observed both in solution (with an apparent Stern–Volmer constant value aKSV up to 1.53 × 103 M−1) and in the vapor phase (50–75% fluorescence quenching of the PU films doped with chemosensors). In the case of nitroaromatic explosives, nitrobenzene (NB), 2,4-DNT, TNT, and 2,4,6-trinitrophenol (TNP or picric acid, PA), pyrene-based iptycenes also demonstrate a good fluorescence-quenching response both in solutions (with apparent Stern–Volmer constant values aKSV = 0.4–8.0 × 103 M−1) and in the vapor phase (up to 90% fluorescence quenching of the PU films doped with chemosensors). The “sphere of action” fluorescence quenching model was suggested.
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    Solvent-free synthesis of 5-(aryl/alkyl)amino-1,2,4- triazines and a-arylamino-2,2 0 -bipyridines with greener prospects
    (RSC Publishing, 2017) Kopchuk, Dmitry S.; Chepchugov, Nikolay V.; Kovalev, Igor S.; Santra, Sougata; Rahman, Matiur; Giri,Kousik; Zyryanov, Grigory V.; Majee, Adinath; Charushin, Valery N.; Chupakhin, Oleg N.
    A green and highly efficient method has been developed for the synthesis of 5-(aryl/alkyl)amino-1,2,4-triazines and α-arylamino-2,2′-bipyridines according to the principles of atom economy. It has been performed by two consecutive solvent-free reaction pathways: the ipso-substitution of a cyano-group in 5-cyano-1,2,4-triazines and the aza-Diels-Alder reaction of the resulting 5-arylamino-1,2,4-triazines with 1-morpholinocyclopentene used as a dienophile. Solvent and catalyst-free conditions, operational simplicity, the compatibility with various functional groups, nonchromatographic purification technique, and high yields are the notable advantages of this procedure. The present methodology possesses a low E-factor.