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Sagade A.A.,Jawaharlal Nehru Centre for Advanced Scientific Research | Venkata Rao K.,New Chemistry Unit | George S.J.,New Chemistry Unit | Datta A.,Indian Association for The Cultivation of Science | Kulkarni G.U.,Jawaharlal Nehru Centre for Advanced Scientific Research
Chemical Communications | Year: 2013

An organic FET employing a single crystal of a donor-acceptor system based on coronene tetracarboxylate and a methyl viologen derivative exhibited an impressive mobility of 0.53 cm2 V-1 s-1, operating under 2 V in the ambient atmosphere. Quantum mechanical calculations have provided an insight into the hole-dominant transport in the crystal. © 2013 The Royal Society of Chemistry.


Raghava B.,University of Mysore | Parameshwarappa G.,New Chemistry Unit | Acharya A.,New Chemistry Unit | Swaroop T.R.,University of Mysore | And 2 more authors.
European Journal of Organic Chemistry | Year: 2014

Efficient routes for the regioselective synthesis of 3,5-bis(het) arylisoxazoles with complementary regioselectivity have been developed. The methods involve the cyclocondensation of hydroxylamine hydrochloride with either 1,3-bis(het)aryl-monothio-substituted 1,3-diketones 1 or with 3-methylthio-1,3-bis(het)aryl-2-propenones 2 under various reaction conditions. In the first protocol, diketones 1 were treated with hydroxylamine hydrochloride in the presence of sodium acetate/acetic acid (pH 2.2) in refluxing ethanol/benzene to give 3,5-bis(het)arylisoxazoles 5, in which the het(aryl) moiety attached to thiocarbonyl group of the monothio-substituted 1,3-diketones is installed at the 3-position. On the other hand, the reaction of hydroxylamine hydrochloride with 3-(methylthio)-1,3-bis(het)aryl-2-propenones 2 in the presence of barium hydroxide in refluxing ethanol gave 3,5-bis(het) arylisoxazoles 6 with complementary regioselectivity in high yields. A probable mechanism for the formation of regioisomeric isoxazoles 5 and 6 from precursors 1 and 2 has been suggested. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Pandeeswar M.,New Chemistry Unit | Senanayak S.P.,Jawaharlal Nehru Centre for Advanced Scientific Research | Narayan K.S.,Jawaharlal Nehru Centre for Advanced Scientific Research | Govindaraju T.,New Chemistry Unit
Journal of the American Chemical Society | Year: 2016

The possibility of designing programmable thin-film supramolecular structures with spontaneous polarization widens the utility of facile supramolecular chemistry. Although a range of low molecular mass molecular single crystals has been shown to exhibit ferroelectric polarization, demonstration of stimuli-responsive, thin-film, solution-processable supramolecular ferroelectric materials is rare. We introduce aromatic π-electron donor-acceptor molecular systems responsive to multiple stimuli that undergo supramolecular chiral mixed-stack charge-transfer (CT) coassembly through the tweezer-inclusion-sandwich process supported by hydrogen-bonding interactions. The structural synergy originating from hydrogen-bonding and chiral CT interactions resulted in the development of spontaneous unidirectional macroscopic polarization in the crystalline nanofibrous hydrogel network, under ambient conditions. Moreover, the tunability of these interactions with optical, mechanical, thermal, and electrical stimuli allowed the design of multistate thin-film memory devices. Our design strategy of the supramolecular motif is expected to help the development of new molecular engineering strategies for designing potentially useful smart multicomponent organic electronics. © 2016 American Chemical Society.


Verma R.K.,Banaras Hindu University | Ila H.,New Chemistry Unit | Singh M.S.,Banaras Hindu University
Tetrahedron | Year: 2010

2-[Bis(methylthio)methylene]-1,3-indanedione has been shown to be a useful three carbon 1,3-dielectrophilic synthon for the highly efficient regiospecific synthesis of a variety of indenofused five- and six-membered heterocycles via heteroaromatic annulation. The methodology has been further elaborated to the corresponding N,S-acetals leading to amino substituted heterocycles, thus providing further point of diversity in the newly synthesized heterocyclic frameworks. Further, the facile access to cytotoxic indeno[2,1-c]quinolin-7-ones and the novel polycyclic heteroaromatics demonstrates the versatility of heteroaromatic annulation protocol via α-oxoketene-S,S-acetal in generating novel biologically important polycyclic heteroaromatics. © 2010 Elsevier Ltd. All rights reserved.


Swaroop T.R.,University of Mysore | Roopashree R.,University of Mysore | Ila H.,New Chemistry Unit | Rangappa K.S.,University of Mysore
Tetrahedron Letters | Year: 2013

A new regiospecific route to 2,4-disubstituted thiophenes has been developed through Simmon-Smith reaction on β-methylthio-α,β- unsaturated ketones. Extension of the reaction to β-ethyl/benzylthio- α,β-unsaturated ketones also gave the corresponding 2,4-disubstituted thiophenes in a regiospecific manner. A probable mechanism involving a carbenoid methylene insertion to divalent sulfur followed by intramolecular aldol condensation has been suggested. © 2012 Elsevier Ltd. All rights reserved.


Swaroop T.R.,University of Mysore | Ila H.,New Chemistry Unit | Rangappa K.S.,University of Mysore
Tetrahedron Letters | Year: 2013

An efficient, regioselective route to 2,4-bis(het)aryl-5(het)aroylthiazoles has been developed by cyclocondensation of thionyl chloride with novel β-(het)arylmethylaminoenones which are readily accessible by the reaction of (het)arylmethylamines with 1,3-bis(het)arylmonothio-1,3-diketones. The method allows entry to 2,4,5-trisubstituted thiazoles, with full control for the introduction of either a (het)aryl group at 2,4 positions or a (het)aroyl group at 5 position of the thiazole ring. © 2013 Elsevier Ltd. All rights reserved.


Haldar R.,New Chemistry Unit | Maji T.K.,New Chemistry Unit | Maji T.K.,Jawaharlal Nehru Centre for Advanced Scientific Research
Journal of Chemical Sciences | Year: 2011

A two-fold interpenetrated microporous bi-pillared-layer framework of Fe(II), {[Fe(2,6- napdc)(4,4'-bipy)](EtOH)(H2O)}n (1) (2,6-napdc =2,6-naphthalenedicarboxylate; 4,4'-bipy=4,4'-bipyridine) composed of mixed ligand system has been synthesized and structurally characterized. The 2,6-napdc linkers form a 2D corrugated sheet of {Fe(2,6-napdc)}n by linking the secondary building unit of Fe2(CO2)2 in the ac plane, which are further connected by double 4,4'-bipy pillars resulting in a bi-pillared-layer type 3D framework. The 3D framework is two-fold interpenetrated and exhibits a 3D channel structure (4.0 × 3.5, 1.5 × 0.5 and 2.2 × 2.1Å2) occupied by the guest water and ethanol molecules. Framework 1 shows high thermal stability, and the desolvated framework (1') renders permanent porosity realized by N2 adsorption profile at 77K (BET surface area of ̃52 m2 g -1). Moreover, the framework 1' also uptakes different solvent vapours (water, methanol and ethanol) and their type-I profile suggest strong interaction with pore surfaces and overall hydrophilic nature of the framework. Temperature dependent magnetic measurements suggest overall antiferromagnetic behaviour in compound 1. © Indian Academy of Sciences.


Lo S.-H.,Northwestern University | He J.,Northwestern University | He J.,Xi'an University of Science and Technology | Biswas K.,Northwestern University | And 3 more authors.
Advanced Functional Materials | Year: 2012

Transmission electron microscopy studies show that a PbTe-BaTe bulk thermoelectric system represents the coexistence of solid solution and nanoscale BaTe precipitates. The observed significant reduction in the thermal conductivity is attributed to the enhanced phonon scattering by the combination of substitutional point defects in the solid solution and the presence of high spatial density of nanoscale precipitates. In order to differentiate the role of nanoscale precipitates and point defects in reducing lattice thermal conductivity, a modified Callaway model is proposed, which highlights the contribution of point defect scattering due to solid solution in addition to that of other relevant microstructural constituents. Calculations indicate that in addition to a 60% reduction in lattice thermal conductivity by nanostructures, point defects are responsible for about 20% more reduction and the remaining reduction is contributed by the collective of dislocation and strain scattering. These results underscore the need for tailoring integrated lengtha scales for enhanced heata carrying phonon scattering in high performance thermoelectrics. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Kumar B.V.V.S.P.,Jawaharlal Nehru Centre for Advanced Scientific Research | Rao K.V.,New Chemistry Unit | Sampath S.,Indian Institute of Science | George S.J.,New Chemistry Unit | Eswaramoorthy M.,Jawaharlal Nehru Centre for Advanced Scientific Research
Angewandte Chemie - International Edition | Year: 2014

Several covalent strategies towards surface chargereversal in nanochannels have been reported with the purpose of manipulating ion transport. However, covalent routes lack dynamism, modularity and post-synthetic flexibility, and hence restrict their applicability in different environments. Here, we introduce a facile non-covalent approach towards chargereversal in nanochannels (<10 nm) using strong charge-transfer interactions between dicationic viologen (acceptor) and trianionic pyranine (donor). The polarity of ion transport was switched from anion selective to ambipolar to cation selective by controlling the extent of viologen bound to the pyranine. We could also regulate the ion transport with respect to pH by selecting a donor with pH-responsive functional groups. The modularity of this approach further allows facile integration of various functional groups capable of responding to stimuli such as light and temperature to modulate the transport of ions as well as molecules. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.


Samai S.,Banaras Hindu University | Chanda T.,Banaras Hindu University | Ila H.,New Chemistry Unit | Singh M.S.,Banaras Hindu University
European Journal of Organic Chemistry | Year: 2013

An efficient and highly regioselective one-pot three-component synthesis of previously inaccessible and synthetically demanding 3-(cycloalkyl/alkyl/ arylamino)-5-aryl/alkylisoxazoles has been achieved by the cyclocondensation of β-oxo dithioesters, amines and hydroxylamine in ethanol at reflux. This transformation proceeds via an in situ generated β-oxothioamide by the reaction of the β-oxo dithioester and amine, which undergoes nucleophilic attack by hydroxylamine followed by intramolecular cyclization with the oxo functionality and subsequent dehydration to give 5-substituted 3-aminoisoxazoles as a single regioisomer in good yields. Furthermore, the mechanism of the reaction has been established experimentally and shown to be in agreement with the hard and soft (Lewis) acid and base (HSAB) theory. A highly regioselective synthesis of 5-substituted 3-aminoisoxazoles has been achieved by a one-pot three-component coupling of β-oxo dithioesters, amines and hydroxylamine in ethanol at reflux via an in situ generated β-oxo thioamide intermediate. The mechanism of the reaction has been established experimentally and shown to be in agreement with the HSAB theory. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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