01768nas a2200169 4500008004100000022001400041245013500055210006900190260009200259300001200351490000700363520104900370100002001419700001501439700001601454856012801470 2005 eng d a0267-829200aEffect of connectivity and terminal functionality on mesophase behaviour of thermotropic liquid crystals containing biphenyl units0 aEffect of connectivity and terminal functionality on mesophase b a4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLANDbTAYLOR & FRANCIS LTDcAPR a499-5120 v323 a

A series of 4,4'-disubstituted biphenyls, designated as series HBC, in which, one substituent is an ester group linked directly to the ring and the other is the hydroxy-containing group O(CH2)(n)OH, have been prepared and analysed by differential scanning Calorimetry, polarizing optical microscopy and X-ray diffraction. The introduction of a trimethylene unit between the ester functional group and the biphenyl moiety of the HBC series gives rise to the HBB series, which did not exhibit liquid crystalline behaviour. Interestingly, mesophase behaviour could be restored by replacing the methylene group ( of the trimethylene unit) that was directly attached to the biphenyl ring by a keto group (HBOB series). When the terminal hydroxy group of these three series was substituted by a group such as acetoxy or hydrogen, the transition temperatures were reduced, and the disappearance of mesophase behaviour was observed in some cases. However, this could be recovered by the replacement of the ester group by a carboxylic acid group.

1 aRanganathan, T.1 aRamesh, C.1 aKumar, Anil uhttps://library.ncl.res.in/content/effect-connectivity-and-terminal-functionality-mesophase-behaviour-thermotropic-liquid-001071nas a2200169 4500008004100000022001400041245011000055210006900165260007100234300001400305490000700319520038500326100002300711700002000734700001600754856013100770 2005 eng d a0021-956800aEffect of NaBr, KCl, KBr, and MgCl2 on viscosities of aqueous glycine and L-alanine solutions at 298.15 K0 aEffect of NaBr KCl KBr and MgCl2 on viscosities of aqueous glyci a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUN a1083-10860 v503 a

Viscosities, η, of glycine and L-alanine are measured in aqueous solutions of NaBr, KCl, KBr, and MgCl2 up to high concentrations at 298.15 K. This study suggests that 1:1 electrolytes enhance the structure making ability of the amino acids whereas MgCl2 does not. The viscosities of the above solutions are correlated using a simple model with two interaction parameters.

1 aBadarayani, Rohini1 aSatpute, D., B.1 aKumar, Anil uhttps://library.ncl.res.in/content/effect-nabr-kcl-kbr-and-mgcl2-viscosities-aqueous-glycine-and-l-alanine-solutions-29815-k-001993nas a2200157 4500008004100000022001400041245012300055210006900178260011000247300001600357490000700373520129700380100001901677700001601696856012301712 2011 eng d a1463-907600aEnthalpic approach to delineate the interactions of cations of imidazolium-based ionic liquids with molecular solvents0 aEnthalpic approach to delineate the interactions of cations of i aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcJUN a14715-147220 v133 a

We present a systematic investigation on the enthalpic assessment of the interactions operating between the cation and anion of four imidazolium ionic liquids with aqueous and various nonaqueous solvents. Accurate experimental information gathered with the help of an isothermal titration calorimeter at 298.15 K has been analyzed for excess partial molar enthalpy of the ionic liquid, H(IL)(E), in terms of hydrophobic and solvation effects. The variations in the limiting excess partial molar enthalpy of the ionic liquid, H(IL)(E infinity), have been correlated with solvent properties. We have quantified the enthalpic effects due to dissociation of ionic liquids in very dilute solutions and to clathrate formation with the increasing concentration of ionic liquid. A change in enthalpic behavior from endothermic to exothermic is observed on increasing the carbon chain length attached to the imidazolium ring. The solvent reorganization around the cationic species has been unraveled by employing the ionic liquid interaction parameters called as H(IL-IL)(E) deduced from the H(IL)(E) data. The apparent relative molar enthalpy, phi(L), derived from H(IL)(E) data has been examined in the light of the specific ion interaction theory as advanced by Pitzer with accurate results.

1 aRai, Gitanjali1 aKumar, Anil uhttps://library.ncl.res.in/content/enthalpic-approach-delineate-interactions-cations-imidazolium-based-ionic-liquids-001295nas a2200265 4500008004100000022001400041245006300055210006100118260011000179300001200289490000700301520043400308653001800742653001800760653002500778653001700803653001300820653001900833653002000852653000900872653001400881100002100895700001600916856009700932 2011 eng d a0376-471000aEutectic mixture-directed kinetics of Diels-Alder reaction0 aEutectic mixturedirected kinetics of DielsAlder reaction aDR K S KRISHNAN MARG, PUSA CAMPUS, NEW DELHI 110 012, INDIAbNATL INST SCIENCE COMMUNICATION-NISCAIRcJUN a788-7920 v503 a

In the search for environmentally benign solvent media, a new class of solvents composed of mixtures of carbohydrates with urea or methylated urea has been noted to be effective in enhancing the reaction rates of a bimolecular organic reaction like the Diels-Alder reaction of cyclopentadiene with methyl acrylate. The viscosity of these media appears to be an important parameter in controlling the second order kinetics.

10acarbohydrates10aCycloaddition10aDiels-Alder reaction10aDimethylurea10akinetics10aReaction rates10asolvent effects10aUrea10aviscosity1 aNagare, Amit, S.1 aKumar, Anil uhttps://library.ncl.res.in/content/eutectic-mixture-directed-kinetics-diels-alder-reaction-002059nas a2200157 4500008004100000022001400041245011100055210006900166260007100235300001400306490000800320520141500328100001901743700001601762856012301778 2014 eng d a1520-610600aElucidation of ionic interactions in the protic ionic liquid solutions by isothermal titration calorimetry0 aElucidation of ionic interactions in the protic ionic liquid sol a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAPR a4160-41680 v1183 a

The strong hydrogen-bonded network noted in protic ionic liquids (PILs) may lead to stronger interactions of the ionic entities of PILs with solvents (water, methanol, ethylene glycol, climethylsulfoxide (DMSO), N,N'-dimethylformamide (DMF)) as compared with those of aprotic ionic liquids (APILs). The PILs used in this work are 1-methylimidazolium tetrafluoroborate, 2-methylpyridinium tetrafluoroborate, and N-methylpyrrolodinium tetrafluoroborate in comparison to 1-butyl-3-methylimidazolium tetrafluoroborate, which is classified as an APIL. In this work, the excess partial molar enthalpy, H-IL(E) obtained from isothermal calorimetric titrations at 298.15 K is used to probe the nature of interactions of the PIL cations with solvent molecules against those present in APIL solvent systems. This work also reports interesting flip-flopping in the thermal behavior of these PIL-solvent systems depending upon the structure of the cationic ring of a PIL. In some cases, these flip-flops are the specific fingerprints for specific PILs in a common solvent environment. The excess partial molar enthalpy at infinite dilution, H-IL(E,infinity), of these PILs bears a critical dependence on the solvent properties. An analysis of relative apparent molar enthalpies, phi(L), of the PIL solutions by the ion interaction model of Pitzer yields important information on ionic interactions of these systems.

1 aRai, Gitanjali1 aKumar, Anil uhttps://library.ncl.res.in/content/elucidation-ionic-interactions-protic-ionic-liquid-solutions-isothermal-titration-001437nas a2200229 4500008004100000022001400041245016200055210006900217260007500286300001400361490000700375520055500382653001800937653001200955653002300967653001600990653001401006100001601020700002401036700001601060856013101076 2015 eng d a1439-423500aExperimental signature of microheterogeneity in ionic liquid-H2O systems and their perturbation by adding Li+ salts: a pulsed gradient spin-echo NMR approach0 aExperimental signature of microheterogeneity in ionic liquidH2O  aPOSTFACH 101161, 69451 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcOCT a2936-29410 v163 a

Distinct microheterogeneity has been observed in the [OMIM]Br-H2O system, which is interestingly perturbed by the addition of Li+ salts, indicating unusual diffusivity of [OMIM]Br and H2O molecules. However, the diffusional dynamics of water clusters show contrasting salting behavior at higher concentrations of Li+ salts, following the classical salting phenomenon in lower amounts. In contrast, the existing microheterogeneity in the [BMIM]Br-H2O system is weak enough to show any perturbation caused by the Li+ salts on the NMR time scale.

10aionic liquids10alithium10amicroheterogeneity10asalt effect10aviscosity1 aNanda, Raju1 aRajamohanan, P., R.1 aKumar, Anil uhttps://library.ncl.res.in/content/experimental-signature-microheterogeneity-ionic-liquid-h2o-systems-and-their-perturbation-101344nas a2200145 4500008004100000245008900041210006900130260000800199300001600207490000700223520081700230100001701047700001601064856011801080 2018 eng d00aEnthalpic interactions in aqueous strong electrolytes upon addition of ionic liquids0 aEnthalpic interactions in aqueous strong electrolytes upon addit cAPR a11089-110990 v203 aThe present study deals with the inter-ionic interactions between strong electrolytes and ionic liquids based on the thermodynamic properties such as excess partial molar enthalpy, H-IL(E), relative apparent molar enthalpy, phi(L), and the enthalpic interaction parameters. The thermodynamic properties of the systems are the key indicators to understand the interionic interactions. We have conducted a systematic investigation of the enthalpic behavior of aqueous solution of salts and ionic liquids and their mixtures. The present study also emphasizes how the H-IL(E) values for the mixture of aqueous solution of ionic liquids and salts deviate from linearity as compared to those of the constituent aqueous ionic liquid or salt. This deviation from linearity for the H-IL(E) values has been discussed here.1 aJain, Preeti1 aKumar, Anil uhttps://library.ncl.res.in/content/enthalpic-interactions-aqueous-strong-electrolytes-upon-addition-ionic-liquids02769nas a2200241 4500008004100000022001400041245018600055210006900241260000900310300001200319490000800331520183400339653000602173653004602179653002902225653004502254653001802299653002902317100001902346700001602365700001702381856012902398 2018 eng d a1010-603000aExcited state intramolecular proton transfer in 1,8-Dihydroxy-9,10-anthraquinone dye: Revealing microstructures in [C(n)mIm][NTf2] and [C(n)mIm][BF4] series of ionic liquid solvents0 aExcited state intramolecular proton transfer in 18Dihydroxy910an cJAN  a111-1210 v3503 a

Excited state intramolecular proton transfer (ESIPT) in 18-dihydroxy-9,10-anthraquinone (18DHAQ) dye has been investigated in two series of 1-alkyl-3-methylimidazolium ([C(n)mIm](+)) based ionic liquid (IL) solvents, [C(n)mlm][NTf2] and [C(n)mlm][BF4], with n = 2, 4, 6, 8 and 10, using steady-state (SS) and time resolved (TR) fluorescence studies. In both the IL series, fluorescence intensity for tautomer (T*) form gradually decreases relative to normal (N*) form with increasing n value for [C(n)mlm](+) cations. Observed results suggest microstructure formation and its consequent effect on the ESIPT process of the dye in these IL solvents. Since more extensive microstructures are likely with larger n values of [C(n)mIm](+) cations, the dye is expectedly solubilized more in the polar microdomains of the solvent microstructures, resulting better stabilization for the more dipolar N* state and hence a higher emission intensity from this state. This proposition is clearly supported by ultrafast (sub-picosecond) fluorescence kinetics for both N* and T* states, though sub-nanosecond TR results indicate very similar fluoresce decays for both N* and T*, suggesting an eventual kinetic equilibrium between two states subsequent to the initial ultrafast and fast forward and backward ESIPT processes. Small differences between the results in the [C(n)mIm][NTf2] and [C(n)mIm][BE4] series of ILs are attributed to dissimilar size, shape and basicity of [NTf2]- and [BF4]- anions, responsible for some characteristic changes in the microstructures formed in the respective solvent series. To the best of our knowledge, present study is the only report demonstrating modulations in the ESIPT process through microstructure formations in neat [C(n)mIm](+) based IL solvents. (C) 2017 Elsevier B.V. All rights reserved.

10a110a1-Alkyl-3-methylimidazolium ionic liquids10a8-Dihydroxyanthraquinone10aEmission modulations of tautomeric forms10aESIPT process10aMicrostructure formation1 aBeniwal, Vijay1 aKumar, Anil1 aPal, Haridas uhttps://library.ncl.res.in/content/excited-state-intramolecular-proton-transfer-18-dihydroxy-910-anthraquinone-dye-revealing02418nas a2200169 4500008004100000245018000041210006900221260000800290300001400298490000700312520171600319100001902035700001602054700001702070700003302087856012802120 2018 eng d00a Excited-state prototropism of 7-hydroxy-4-methylcoumarin in [C(n)mim][BF4] series of ionic liquid-water mixtures: insights on reverse micelle-like water nanocluster formation0 aExcitedstate prototropism of 7hydroxy4methylcoumarin in CnmimBF4 cSEP a1256-12660 v173 aThis study explores the excited state prototropic behavior of the fluorophore, 7-hydroxy-4-methylcoumarin (7H4MC), in the [C(n)mim][BF4] (n = 2, 4, 6, 8, 10) series of ionic liquid (IL)-water mixtures at low water contents. In pure IL media, 7H4MC exists in the neutral form in both ground and excited states. However, on addition of water to the ILs, the excited neutral form of the dye is gradually converted to the anionic and the tautomeric species, leading to characteristic changes in the emission spectra. The similarity in the spectral features of 7H4MC in the IL-water system with that in a conventional reverse micelle system rather than with organic solvent-water mixtures, suggests that in the presence of water, the ILs are organized into reverse micelle-like structures with the consequent formation of confined water pockets. The results further suggest that formation of water nanoclusters and the ensuing changes in excited state prototropic behavior of the dye, is facilitated by increase in the alkyl chain length of the IL cation. These propositions are supported by time-resolved fluorescence studies. To the best of our knowledge this is the first report on proton transfer reaction in IL-water mixtures at low water contents. Considering that ILs are useful as solvents and surfactants, and IL-water mixtures in particular have applications in chemical extractions and biocatalysis, an understanding of the structural organization and water pool formation in these systems is quite important. The insights obtained from the prototropic transformations of 7H4MC are significant not only for fundamental self-assembly studies, but also for the development of ILs as chemical reaction media.1 aBeniwal, Vijay1 aKumar, Anil1 aPal, Haridas1 aChoudhury, Sharmistha, Dutta uhttps://library.ncl.res.in/content/excited-state-prototropism-7-hydroxy-4-methylcoumarin-cnmimbf4-series-ionic-liquid-water