1. Journal Articles
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Item Trifluoromethyl-quinolin-yl-thio-propanohydrazide as an effective inhibitor of mild steel corrosion in HCl solution(2006) Ramesh, Saliyan, V.; Adhikari, A.V.3-{[8-(trifluoromethyl)quinolin-4-yl]thio}propanohydrazide(TFQTPH) was synthesized, characterized and tested as a corrosion inhibitor for mild steel in 1 M HCl and 2 M HCl solution using different techniques: potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that TFQTPH is an excellent inhibitor for mild steel in acid medium. The inhibition was assumed to occur via adsorption of the inhibitor molecule on the metal surface. In the temperature range 20� to 60� C, the TFQTPH adsorption follows Langmuir isotherm model. The protection efficiency increased with increasing inhibitor concentration (10 to 500 ppm), even at higher temperature also, it recorded good inhibition efficiency. � 2006 SAEST.Item Z-scan and degenerate four wave mixing studies on newly synthesized copolymers containing alternating substituted thiophene and 1,3,4-oxadiazole units(2006) Kiran, A.J.; Udayakumar, D.; Chandrasekharan, K.; Adhikari, A.V.; Shashikala, H.D.The third-order nonlinear optical properties of newly synthesized copolymers containing alternating substituted thiophene and 1,3,4-oxadiazole units have been studied in DMF solution at 532 nm by using single beam Z-scan and degenerate four wave mixing techniques with nanosecond laser pulses. The variation of nonlinear response among the copolymers clearly indicates the dependence of ?(3) on donor and acceptor type of units present in the copolymers. The nonlinear refractive index, n2, of the investigated copolymers is found to be negative and the magnitude is as high as 10-10 esu. All samples exhibit strong reverse saturation absorption at the wavelength used and show good optical limiting of nanosecond pulses. The concentration dependence of n2 and the two-photon absorption coefficient (?) has been studied. � 2006 IOP Publishing Ltd.Item Third-order nonlinear optical susceptibilities of new copolymers containing alternate 3,4-dialkoxythiophene and (1,3,4-oxadiazolyl)pyridine moieties(2009) Hegde, P.K.; Adhikari, A.V.; Manjunatha, M.G.; Poornesh, P.; Umesh, G.A new series of conjugated copolymers (P1-P3) consisting of alternate 3,4-dialkoxythiophene and (1,3,4-oxadiazolyl)pyridine moieties have been synthesized using the precursor polyhydrazide route. They have been characterized by FTIR, 1H NMR spectral and elemental analyses. These copolymers possess well defined structure and exhibit good thermal stability with the onset decomposition temperature in nitrogen at around 300 C. Their molecular weights were determined by gel permeation chromatography (GPC). The optical and charge-transporting properties of the copolymers were investigated by UV-visible spectroscopy, fluorescence emission spectroscopy and cyclic voltammetry. Their UV-visible absorption spectra showed a ?max at around 342 nm and displayed bluish-green fluorescence in solution state. The band gaps were found to be at about 2.55 eV for all the copolymers. The third-order nonlinear optical properties (NLO) of these copolymers were studied by Z-scan technique. The measurements were performed at 532 nm with 7 ns laser pulses using a Nd:YAG laser in solution form. The real part of ?(3) were estimated to be -0.881 10-12, -0.901 10-12 and -1.030 10-12 esu for P1, P2 and P3 respectively. The imaginary part of ?(3) for the copolymers P1, P2 and P3 were determined to be 0.192 10-12, 0.253 10-12 and 0.272 10-12 esu respectively. The copolymers exhibit strong reverse saturable absorption and good optical limiting behaviour at 532 nm. 2008 Elsevier B.V. All rights reserved.Item Third-order nonlinear optical studies of newly synthesized polyoxadiazoles containing 3,4-dialkoxythiophenes(2006) Udayakumar, D.; John, Kiran, A.; Adhikari, A.V.; Chandrasekharan, K.; Umesh, G.; Shashikala, H.D.The third-order nonlinear optical properties of newly synthesized soluble polyoxadiazoles containing 3,4-dialkoxythiophenes were investigated by using Z-scan and degenerate four-wave mixing (DFWM) techniques. The measurements were performed at 532 nm with 7 ns pulses from a Nd:YAG laser. We found a good agreement between the values of ?(3) determined from both the experiments. Z-scan results indicate a negative nonlinear refractive index, n2, whose magnitude is of the order of 10-10 esu for all the copolymers. The variation of nonlinear response among the copolymers clearly indicates the dependence of ?(3) on donor and acceptor type of units present in these copolymers. The copolymers exhibit strong reverse saturable absorption and good optical limiting properties at 532 nm. 2006 Elsevier B.V. All rights reserved.Item Synthesis of some new pyrazolines and isoxazoles carrying 4-methylthiophenyl moiety as potential analgesic and antiinflammatory agents(2009) Karabasanagouda, T.; Adhikari, A.V.; Girisha, M.A series of new pyrazolines 3a-m and isoxazoies 4a-k have been synthesized from 4-acetylthioanisole, 1 with aryl aldehydes through ?, ?-unsaturated ketones. The structures of the newly synthesized compounds have been confirmed on the basis of elemental analysis and spectral studies. The newly synthesized title compounds have been tested for their analgesic and antiinflammatory activity. Some of the compounds exhibited encouraging results.Item Synthesis of some novel 2,4-disubstituted thiazoles as possible antimicrobial agents(2008) Wagle, S.; Adhikari, A.V.; Kumari, N.S.A series of 4-aryl-2-(3-methyl-7-substituted quinoxaline-2-one-1-yl)-1,3- thiazoles (6a-l) and 4-substituted alkyl-2-(3-methyl-7-substituted quinoxaline-2-one-1-yl)-1,3-thiazoles (8a-i) were synthesized in good yield by condensing 2-(3-methyl-7-substituted l,2-oxoquinoxalin-1(2H)-yl)ethanethioamides (5a-c) with substituted phenacyl bromide and dichloroacetone followed by treatment with secondary amines, respectively. The intermediates, 5a-c were conveniently obtained by reacting phosphorus pentasulphide with 2-(3-methyl-7-substituted-2-oxoquinoxalin-1(2H)-yl) acetamides (4a-c) which in turn were synthesized from ethyl (3-methyl-7-substituted-2-oxoquinoxalin-1(2H)- yl) acetates (3a-c) by aqueous ammonia treatment. The newly synthesized compounds were characterized by IR, 1H NMR, 13C NMR, and Mass spectral and elemental analyses. These compounds were screened for in vitro antibacterial activity against five pathogenic strains and antifungal activity against four fungi. Preliminary results revealed that some of the synthesized compounds showed promising antimicrobial activity. Copyright Taylor & Francis Group, LLC.Item Synthesis of some new 2-(3-methyl-7-substituted-2-oxoquinoxalinyl)-5-(aryl) -1,3,4-oxadiazoles as potential non-steroidal anti-inflammatory and analgesic agents(2008) Wagle, S.; Adhikari, A.V.; Kumari, N.S.Ethyl (3-methyl-7-substituted-2-oxoquinoxalin-1(2H)-yl) acetates 2a-c are prepared by the condensation of ethyl chloroacetate with 3-methyl-7-substituted quinoxalin-2(1H)-ones 1a-c. The reaction of 2a-c with hydrazine hydrate furnished 2-(3-methyl-7-substituted-2-oxoquinoxalin-1(2H)-yl) acetohydrazides 3a-c, which on cyclisation with substituted aromatic carboxylic acids in the presence of phosphorous oxychloride give 3-methyl-7-substituted-1-[(5-aryl-1,3, 4-oxadiazol-2-yl)methyl]quinoxalin-2(1H)-ones 4a-y. Further, the compounds 3a-c on cyclisation with carbon disulphide in methanolic potassium hydroxide yielded 1-[(5-mercapto-1,3,4-oxadiazol-2-yl)methyl]-3-methyl-7-substituted quinoxalin-2(1H)-ones 5a-c. Finally, the compounds 5a-c are converted to 3-methyl-7-substituted-1-{[5-(alkylsulfanyl)-1,3,4-oxadiazol-2-yl]methyl} quinoxalin-2(1H)-ones 6a-i by reacting them with different alkyl halides. The newly synthesized compounds have been characterized by IR, 1H NMR, 13C NMR and mass spectral data and elemental analysis. Selected compounds are screened for in vivo anti-inflammatory and analgesic activity. Few of them exhibited promising activity.Item Synthesis of some new 4-styryltetrazolo[1,5-a]quinoxaline and 1-substituted-4-styryl[1,2,4]triazolo[4,3-a]quinoxaline derivatives as potent anticonvulsants(2009) Wagle, S.; Adhikari, A.V.; Kumari, N.S.4-Methyltetrazolo[1,5-a]quinoxaline (3) was prepared by the azide cyclocondensation of 2-chloro-3-methylquinoxaline (2). The reaction of 3 with aromatic aldehydes furnished 4-styryltetrazolo[1,5-a]quinoxalines (4a-f). Compound 2, on treatment with hydrazine hydrate gave 2-hydrazino-3-methylquinoxaline (5). The ring closure of 5 was achieved by the reaction of orthoesters and trifluoroacetic acid to yield 4-methyl-1-(substituted)[1,2,4]triazolo[4,3-a]quinoxalines (7a-c). Further, reaction of 7a-c with different aromatic aldehydes furnished the title compounds, 4-styryl-1-(substituted)[1,2,4]triazolo[4,3-a]quinoxalines (8a-i) in good yield. In another scheme, the hydrazino compound 5 was treated with different aromatic aldehydes to yield corresponding N-arylidenehydrazino quinoxalines (6a-d). Further, the oxidative cyclization of hydrazones by nitrobenzene yielded 1-aryl-4-methyl[1,2,4]triazolo[4,3-a]quinoxalines (7d-g), which on condensation with aromatic aldehydes gave the title compounds, 1-aryl-4-styryl[1,2,4]triazolo[4,3-a]quinoxalines (8j-u). The newly synthesized compounds have been characterized by FTIR, 1H NMR, 13C NMR and mass spectral data, followed by elemental analysis. Some of the compounds were screened for in vivo anticonvulsant activity. Few of them exhibited promising results. 2008 Elsevier Masson SAS. All rights reserved.Item Synthesis of some biologically active 2,4'-bipyridine-5-carbonitriles carrying the 4-hydroxyphenylthio moiety [Russian Source](2009) Karabasanagouda, T.; Adhikari, A.V.; Parameshwarappa, G.A series of new 4-aryl-2'-[(4-hydroxyphenyl)thio]-6oxo-1,6-dihydro-2,4'-bipyridine-5-car bonitriles (3a-k) and 6-amino-4aryl-2'-[(4-hydroxyphenyl) thio]-2,4'-bipyridine-5-carbonitriles (4a-h) were synthesized from 4-hydroxythiophenol (1). The reaction of 4-hydroxythiophenol with 4-acetyl-2-chloropyridine yielded 1-{2-[(4-hydroxyphenyl)thio]pyridin-4-yl}ethanone (2). Further treatment of 2 with ethyl cyanoacetate in the presence of ammonium acetate with various aromatic aldehydes furnished the compounds 3a-k. On the other hand, condensation of 2 with aromatic aldehydes in the presence of alcoholic malononitrile in ammonium acetate gave compounds 4a-h. The structures of the newly synthesized compounds were established on the basis of their elemental analysis, as well as their IR, 1H- and 13C-NMR and mass spectral data. All the title compounds were subjected to in vitro antibacterial testing against two strains and antifungal screening against two fungi. Some of the compounds showed promising activity. 2009 Copyright (CC) SCS.Item Synthesis of some new 2-(4-alkylthiophenoxy)-4-substituted-1, 3-thiazoles as possible anti-inflammatory and antimicrobial agents(2008) Karabasanagouda, T.; Adhikari, A.V.; Dhanwad, R.; Parameshwarappa, G.A series of new 2-{[4-(alkylthio)phenoxy]methyl}-4-substituted-1,3- thiazoles 4a-q, 6a-j have been synthesized from ethyl [4-(alkylthio)phenoxy] acetates 1a,b through multi-step reaction sequence. The structures of new compounds have been established on the basis of their elemental analysis and IR, 1H and 13C NMR and mass spectral data. Selected title compounds have been evaluated for anti-inflammatory activity and in vitro antibacterial testing against two pathogenic strains and antifungal screening against two fungi.