Dept of Chemistry

Poly(vinyl chloride) (PVC)-based membrane of pentathia-15-crown-5 exhibits good potentiometric response for Hg2+ over a wide concentration range (2.51 × 10−5 to 1.00 × 10−1 mol dm−3) with a slope of 32.1 mV per decade of Hg2+ concentration. The response time of the sensor is as fast as 20 s. The electrode has been used for a period of six weeks and exhibits fairly good discriminating ability towards Hg2+ in comparison to alkali, alkaline and some heavy metal ions. The electrode can be used in the pH range from 2.7 to 5.0.

in PVC and polystyrene binders have been investigated as Ni'+-selective sensors. The PVC membranes containing macrocycles, di-n-butylphthalate and dioctylphthalate as plasticizing solvent mediators and sodium tetraphenylborate as an anion excluder show near-Nernstian response in the concentration range = 10-5-10-' mol l-', while polystyrenebased membranes exhibit linearity in the concentration range = 10-6-10-' mol 1-l. These membranes have response times as fast as 15 s and can be used over a period of six months. The electrodes work in the pH range 1.7-5.4 and also perform well in alcohol-water mixtures with alcoholic content up to 50%. The selectivity coefficient values reveal that the electrodes respond to Ni2+ ions selectively over a large number of cations. The membrane has also been used as an indicator electrode for the determination of the end point in the potentiometric titration of Ni2+ against oxine.

Poly(vinylchloride) (PVC) and polystyrene based uranyl ion-selective electrodes have been constructed using 2-hydroxyacetophenoneoxime-thiourea-trioxane resin as electroactive material. For PVC based membranes dibutylphthalate (DBP) and dioctylphthalate (DOP) were used as plasticizing solvent mediators. These membrane electrodes work in the concentration range of ca. 10−5–10−1 M with a response time as fast as 30 s. The useful working pH range is 2.5–3.5 and the electrodes perform satisfactorily up to 20 % (v./v.) partially nonaqueous content. The electrodes were used over a period of 4 months with good reproducibility (standard deviation = 0.5 mV). Further, the selectivity coefficient values of the order 0.1 for mono- and bivalent ions indicate moderate selectivity for UO ions over the interfering ions.

AbstractÐA zinc complex of the organic ion exchanger, bis(2,4,4-trimethylpentyl) dithiophosphinic acid, has been used as an electroactive material for the preparation of PVC-based Zn 2+ -selective electrodes. The PVC matrix incorporating sodium tetraphenylborate (NaTPB) as the anion excluder and dibutyl(butyl)phosphonate (DBBP) as the solvent mediator along with the above complex in the ratio 7:29:5:59 (Zn±Cyanex-301:DBBP:NaTPB:PVC) exhibited a working concentration range of 2.8 Â 10 À5 ±1.0 Â 10 À1 M, with a slope of 30.1 mV per decade of activity and a fast response time of 15 s. The valid pH range for the membrane sensor is 2.1±6.9 and it can also be used in partially non-aqueous medium having upto 10% (v/v) non-aqueous content. The sensor exhibits good selectivity over a number of other cations and has been applied as indicator electrode in the potentiometric titration of Zn 2+ against EDTA for the determination of end point. #

A 20% (w./w.) polystyrene-based heterogeneous membrane of inorganic ion-exchanger, cerium(IV) vanadate, has been prepared and used as a bismuth(III) selective electrode. The electrode gives linear potential response in the concentration range 8.0 × 10−5-1.0 × 10−1 mol L−1 with a slope of 19.2 mV per decade of concentration and a fast response time of 50s. The electrode functions well in the pH range 2.0–4.0, in partially nonaqueous media up to 25% (v./v.) alcoholic content and was used over a period of 4 months without any significant drift in potentials. It exhibits selectivity for Bi3+ over a large number of metal ions and can be used as an indicator electrode to determine Bi3+ by potentiometric titration with EDTA.

Poly(vinyl chloride) based membranes of di-(2-ethylhexyl)phosphoric acid (DEHPA) and dibutyl(butyl)phosphonate (DBBP) have been prepared and investigated as VO 2 + -selective sensors. The membranes containing DEHPA/DBBP and sodium tetraphenylborate, an anion excluder, show near-Nernstian/Nernstian response in the concentration range 10 − 5 -10 − 1 M. The sensors exhibit a fast response time and good selectivity for VO 2 + over a number of other cations. Quantitative determination of vanadium in waste V 2 O 5 catalyst has been achieved by these sensors and they have also been used as indicator electrodes for the determination of the end point in the potentiometric titration of VO 2 + against EDTA.

The amino acid condensation reaction on a heterogeneous mineral surface has been regarded as one of the important pathways for peptide bond formation. Keeping this in view, we have studied the oligomerization of the simple amino acids, glycine and alanine, on nickel ferrite (NiFe₂O₄), cobalt ferrite (CoFe₂O₄), copper ferrite (CuFe₂O₄), zinc ferrite (ZnFe₂O₄), and manganese ferrite (MnFe₂O₄) nanoparticles surfaces, in the temperature range from 50-120 °C for 1-35 days, without applying any wetting/drying cycles. Among the metal ferrites tested for their catalytic activity, NiFe₂O₄ produced the highest yield of products by oligomerizing glycine to the trimer level and alanine to the dimer level, whereas MnFe₂O₄ was the least efficient catalyst, producing the lowest yield of products, as well as shorter oligomers of amino acids under the same set of experimental conditions. It produced primarily diketopiperazine (Ala) with a trace amount of alanine dimer from alanine condensation, whil...

Ribonucleotides (RMPs) are the building blocks of genetic material consisting of a sugar group, a phosphate group and a nucleobase. Prussian blue (PB) is an ancient compound which is supposed to have formed under the conditions of primitive Earth. The interaction between nucleotides and mineral surfaces is of primary importance in the context of prebiotic chemistry. In the present work, the adsorption of RMPs on PB has been studied in the concentration range 0.4 × 10−4–3.0 × 10−4 M of RMPs at pH 7.5, T = 27°C and found to be 53.1, 41.7, 25.8 and 24.0% for adenosine 5′-monophosphate (5′-AMP), guanosine 5′-monophosphate, cytidine 5′-monophosphate and uridine 5′-monophosphate, respectively. Optimum conditions for the adsorption were studied as a function of concentration, time, amount of adsorbent and pH and data obtained were found to fit the Langmuir adsorption isotherm. Langmuir constants (KL and Xm) values were calculated. Fourier transform infrared spectroscopy, Raman spectroscopy...

Interaction of ribonucleotides with zinc ferrite nanoparticles (~15 nm) prepared by the solegel method was studied at physiological pH (~7.0). Ultraviolet (UVeVis), Fourier transform infrared (FT-IR), Raman spectroscopy and field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) were employed to investigate the interaction of ribonucleotides with zinc ferrite surface. Langmuir and Freundlich adsorption models were used to describe the equilibrium isotherms in the concentration range of 1.0 Â 10 À4 MÀ4.0 Â 10 À4 M of ribonucleotides. The maximum adsorption capacity determined for 5 0-GMP, 5 0-AMP, 5 0-UMP, 5 0-CMP was 22.37 mg/g, 17.42 mg/g, 16.03 mg/g and 14.03 mg/g, respectively. Langmuir model was found to show the best fit for experimental data. Adsorption kinetics were studied by pseudo-first order and pseudo-second order kinetic models, and the adsorption process was best described by the pseudo-second order kinetic model. FE-SEM images clearly showed that ribonucleotide adheres onto the zinc ferrite nanoparticles surface. AFM analysis demonstrated that the root mean square roughness (Rms, S q) and average roughness (S a) increased from 0.98 nm to 1.80 and 0.67 nme1.38 nm, respectively following exposure to ribonucleotide. FT-IR spectroscopy revealed that the zinc ferrite nanoparticles interact strongly with the phosphate, carbonyl and amino groups of ribonucleotides. Raman spectra of 5 0-AMP-zinc ferrite adduct showed the participation of amino and a phosphate group with zinc ferrite nanoparticles surface.

Based on the hypothesis on the presence of double metal cyanides in the primordial oceans, a series of nano-sized metal(II) hexacyanocobaltate(III) (MHCCo) with the general formula: M 3 [Co(CN) 6 ] 2 •xH 2 O (where M = Zn, Fe, Ni and Mn) has been synthesized. Surface interaction of aromatic amines, namely aniline, 4-chloroaniline, 4-methylaniline and 4-methoxyaniline with MHCCo particles has been carried out at the concentration range of 100-400 µM at pH~7.0. The percentage binding of aromatic amines on MHCCo surface was found to be in the range of 84%-44%. The trend in adsorption was in accordance to the relative basicity of the studied amines. At the experimental pH, amines reacted rapidly with the surface of the iron(II) hexacyanocobaltate, producing colored products that were analyzed by Gas Chromatography Mass Spectroscopy (GC-MS). GC-MS analysis of the colored products demonstrated the formation of dimers of the studied aromatic amines. Surface interaction of aromatic amines with MHCCo was studied by Fourier Transform Infrared (FT-IR) spectroscopy and Field Emission Scanning Electron Microscopy (FE-SEM). The change in amine characteristic frequencies, as observed by FT-IR, suggests that interaction took place through the NH 2 group on amines with metal ions of hexacyanocobaltate complexes. FE-SEM studies revealed the adherence of 4-methoxyaniline on zinc hexacyanocobaltate particles surface. We proposed that MHCCo might have been formed under the conditions on primitive Earth and may be regarded as an important candidate for concentrating organic molecules through the adsorption process.

The quantum chemical study of one-, two-, and three-photon absorption (1PA, 2PA, and 3PA) properties for a set of compact fluorene derivatives (FD) with combination of different donor and acceptor moieties on both sides of fluorene ring system is presented. The main goal of the study is to pack large two-photon (2P) and three-photon (3P) activity into smallest possible chromophore. Linear, quadratic, and cubic response time-dependent density functional theory was used to calculate 1PA, 2PA, and 3PA properties, respectively. We used CAMB3LYP/cc-pVDZ level of theory for all the property calculations. The 2P and 3P transition probabilities were recalculated using two-state model approach and found to be in good agreement with the response theory results for first excited state. To include the contributions from higher states, the three-state model was also employed to recalculate the 2P transition probabilities and found to be in excellent agreement with response theory. The 2P/3P tensor elements were also analyzed to find reasons behind large 2P/3P activities. All the orbitals involved in transition processes were studied in detail by both molecular orbital pictures (qualitatively) and overlap diagnostic Λ-values (quantitatively). The study reveals that the novel fluorene derivatives FD-12 and FD-13 have shown large 2PA cross-section values of 1100 G.M. and 1030 G.M.; and 3PA transition probabilities of 6.10 × 10 10 a.u. and 4.85 × 10 10 a.u., respectively, for transition S 0 → S 1. The largest 3PA transition probability of 4.04 × 10 11 a.u. was found with FD-12 for S 0 → S 2 excitation. The linear relationship between Λ-values and 2PA cross-section values was also studied.

The present work aims to study solvent effects on the polarizability (a), static first hyperpolarizability (b) and one-and two-photon absorption (OPA and TPA) properties of a new class of molecules viz. triply twisted Mö bius annulenes, recently studied by us in vacuum phase [Kundi et al., Phys. Chem. Chem. Phys., 2015, 17, 6827]. We have employed linear and quadratic response theories within the framework of time-dependent density functional theory with the CAM-B3LYP functional and a cc-pVDZ basis set to calculate different parameters. The microscopic details of the said properties have been studied using a two-state model (2SM) approach, which performs very well in the case of b and TPA of the first excited state of all the systems. However for the second excited state, the 2SM results are far from those of response theory. In fact, in comparison to response theory, 2SM predicts an opposite trend for the TP activity of some of the model systems, indicating a significant contribution from the other higher excited states. The anomaly between the 2SM approach and response theory has been resolved by incorporating three states in the calculations.

In the present work, we have studied the gas phase one-and two-photon absorption (OPA and TPA) properties of the first two excited states of the triply twisted Mö bius annulene molecule (G. R. Schaller, et al., Nat. Chem. 2014, 6, 608) and five model systems substituted with different donor and acceptor groups. The main purpose of this study is to explore the OPA and TPA properties of this newly synthesized molecule and the unique p-conjugation provided by it. We have used the linear and quadratic response theory methods with the CAMB3LYP functional and the cc-pVDZ basis set for calculating the required parameters. Our results indicate that in the absence of any directive force (i.e. the donor–acceptor groups) the unsubstituted molecule is completely TP inactive. However, as soon as we insert the donor–acceptor group the system becomes TP active which can further be enhanced (up to 3640 GM in our case) by changing the donor–acceptor groups. We have explained the results by performing a two-state model calculation and by analyzing the TP tensor elements and the orbitals involved in the transition processes.

A detailed theoretical study of linear and non-linear optical susceptibilities (NLOS), one-and two-photon absorption (OPA and TPA) properties for a series of push–pull trans-stilbene (TSB) derivatives with introduction of different electron donor (D) and acceptor (A) groups on either side of the TSB ring system is presented. The objective of the work is to design new TSB derivatives with large TPA cross-section values and to explore their linear and non-linear optical susceptibilities, OPA and TPA properties. We have used linear and quadratic response theory methods and CAM-B3LYP functional in conjunction with the 6-31+G* basis set for all property calculations. We have explained the results of the first hyperpolarizability and TP transition probability using two-state model (2SM) calculations, the results of which are in excellent agreement with the response theory methods. The TP tensor elements have been analysed to explain the large TP activity of molecules. Orbitals involved in the transition processes have been studied both qualitatively (molecular orbital pictures) and quantitatively (L-values) in order to explain the nature of charge transfer in different TSB derivatives. The study reveals that the novel derivatives TSBD-10, TSBD-11, TSBD-12 and TSBD-13 have large non-linear optical susceptibilities and TPA cross-section values, the largest being found for TSBD-13 (5560 G.M.).

Densities, µ, and speed of sound, u for binary mixtures dipropylene glycol monomethyl ether and tripropylene glycol monomethyl ether with 2-methyl-1-propanol, 3-methyl-1-butnaol, and 2-methyl-2-butanol at T = 288.15, 298.15, and 308.15 K and atmospheric pressure over the entire range of composition have been measured using an AntonPaar DSA 5000M densimeter. Excess molar volumes V E m , and deviations in isentropic compressibilities ¦¬ S have been calculated from experimental densities and speeds of sound. Comparison of the results has been made with earlier results. Deviations in intermolecular free length and deviations in acoustic impedance have also been calculated. The results have been discussed in terms of intermolecular interactions between component molecules of the mixtures.

Viscosities at T = (298.15 and 308.15) K and atmospheric pressure for binary liquid mixtures of cyclopentane with 2-methyl-1-propanol, 3-methyl-1-butanol and 2-methyl-2-butanol over the whole composition range have been measured as a function of composition using an Ubbelohde viscometer. The deviations in viscosity and excess free energy of activation for viscous flow have been calculated from experimental data. The results have been compared with earlier results of n-alkanols. A number of approximations used to obtain deviation in viscosities have been analysed. Further, different correlations were used to correlate the viscosity data.

Direct resolution of enantiomers has acquired greater analytical importance. Of various chromatographic techniques, TLC continues to enjoy considerable reputation for the purpose. The present paper deals with an important and yet less explored aspect of TLC i.e. impregnation. Methods of impregnation of thin layer material with a variety of reagents and the role of impregnating reagents in resolving compounds on these layers, with special reference to main/basic approaches of impregnation as applied to direct enantiomeric resolution, are discussed.

Synthesis of N-succinimidyl-(S)-2-(6-methoxynaphth-2-yl) propionate was carried out by the reaction of (S)-naproxen with N-hydroxysuccinimide in the presence of dicyclohexyl carbodiimide. It was characterized and was used as a chiral derivatizing reagent, under mild conditions, to form diastereomers of dl-penicillamine which were resolved by reversed-phase high-performance liquid chromatography using triethyl ammonium phosphate buffer (pH 4.0, 5 mM)-acetonitrile (linear gradient (30 min) of acetonitrile from 30 to 70%). Excellent separation was achieved with gradient mobile phase. The detection limit was at pmol level.