Computational Sciences - Research Publications

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    3-Cyano-2-azaanthracene-based ‘‘push-pull” fluorophores: A one-step preparation from 5-cyano-1,2,4-triazines and 2,3-dehydronaphthalene, generated in situ
    (Elsevier, 2016) Kopchuk, Dmitry S.; Chepchugov, Nikolay V.; Taniya, Olga S.; Khasanov, Albert F.; Giri,Kousik; Kovalev, Igor S.; Santara, Saugata; Zyryanov, Grigory V.; Majee, Adinath; Rusinov, Vladimir L.; Chupakhin, Oleg N.
    A facile one-step approach towards 3-cyano-2-azaanthracenes via the [4+2] cycloaddition reaction between 5-cyano-1,2,4-triazines and 2,3-dehydronaphthalene, generated in situ from commercially available 3-amino-2-naphthoic acid, has been reported. The influence of the 1,2,4-triazine ring sub- stituents nature on the product yield has been studied. The observed experimental results were con- firmed by DFT calculations of the HOMO-LUMO energy levels of the both cycloaddends. The photophysical properties of the products have been investigated.
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    Azaanthracenes via Inverse Electron-Demand Diels–Alder Reaction
    (THIEME STUTTGART, 2016) Kopchuk, Dmitry S.; Chepchugov, N. V.; Taniya, Olga S.; Khasanov, A.F.; Giri,Kousik; Kovalev, Igor S.; Santra, S.; Zyryanov, Grigory V.; Majee, A.; Rusinov, V.L.; Chupakhin, O.N.
    Significance: Azaanthracenes are important fluo- Comment: The benzyne derivative is generated in rophores that are used in a number of applications such as metal or pH sensors. In this report the authors describe a new synthesis of this type of structure via an inverse electron-demand aza- Diels–Alder reaction between a benzyne derivative and an electron-deficient triazine. situ from the diazotization of 2-amino-3-naphthoic acid. It was found that the cyano activating group at the 5-position of the triazine is crucial for the reaction to take place because it offers a smaller energy difference between the cycloaddition HOMO and LUMO.
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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.
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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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    Relative stabilities and the spectral signatures of stacked and hydrogen-bonded dimers of serotonin
    (Taylor and Francis Ltd., 2015) Dev, S.; Giri,Kousik; Majumder, M.; Sathyamurthy, N.; Dev, S.; Giri, K.; Majumder, M.; Sathyamurthy, N.
    The O-HsssN hydrogen-bonded dimer of serotonin is shown to be more stable than the stacked dimer in its ground electronic state, by using the M?ller-Plesset second-order perturbation theory (MP2) and the 6-31g??basis set. The vertical excitation energy for the lowest ? ? ?? transition for the monomer as well as the dimer is predicted by time-dependent density functional theory. The experimentally observed red shift of excitation wavelength on oligomerisation is explained in terms of the change in the HOMO-LUMO energy gap due to complex formation. The impact of dimer formation on the proton magnetic resonance spectrum of serotonin monomer is also examined. ? 2015 Taylor and Francis.