Avinash L. Puyad

The density, viscosity and structural properties of aqueous ethambutol hydrochloride solutions

Ethambutol (EMB) is a bacteriostatic antimycobacterial drug prescribed to treat tuberculosis. It is bacteriostatic against actively growing TB bacilli. The density and viscosity of aqueous ethambutol hydrochloride solutions have been studied at 298.15, 301.15 and 304.15 K and at different concentrations (0.255, 0.168, 0.128, 0.087, 0.041, and 0.023 mol dm−3). The apparent molar volume of these solutions for different temperatures and concentrations was calculated from the density data. The relative viscosities of drug solutions have been analysed by Jones-Dole equation. The limiting apparent molar volumes have been evaluated for different temperatures. The different properties have been used to study structural properties, structure formation and breaking properties of drug and solute-solvent interactions in solutions.

The density and viscosity of aqueous solutions of sodium 2-({[4-(3-methoxypropoxy)-3-methylpyridin-2-yl]methyl}sulfinyl)benzimidazol-1-ide and solute-solvent molecular interactions study

This paper reports the measured density and viscosity of aqueous solutions of different concentrations of antiulcer drug, sodium 2-({[4-(3-methoxypropoxy)-3-methylpyridin-2-yl]methyl}sulfinyl)benzimidazol-1-ide at 40°C. The apparent molar volumes of different solutions were computed using density data. Apparent molar volume at infinite dilution which reflects solute-solvent interaction and Sv, the parameter that represents solute-solute interaction has been determined graphically by using Masson’s equation. Viscosity data has been analyzed by Jone-Dole equation. Viscosity coefficients A and B were determined and explained in terms of solute-solute, solute-solvent interactions and structure making/breaking ability of said drug.

A novel donor-acceptor receptor for selective detection of Pb2+ and Fe3+ ions.

An efficient and highly selective colorimetric and fluorescent receptor DTPDA has been synthesized for sensitive detection of Pb(2+) and Fe(3+) cations. The sensor DTPDA produces a facile, cost-effective and naked eye sensing platform to determine trace amounts of Pb(2+) and Fe(3+) metal ions by complexation with pendent S-termini of thiophenes, which commonly coordinates to central N-termini of pyridine.

Hydrogen sulfate ion sensing in aqueous media based on a fused pyrimido benzothiazole derivative

A sensitive and selective receptor 3-cyano-4-imino-2-methylthio-4H-pyrimido[2,1-b][1,3]benzothiazole (SVK-1) bearing a fused pyrimido benzothiazole structure was developed for the recognition of HSO4− anions. UV-vis and fluorescence emission spectroscopy were employed for the recognition for HSO4− over other anions such as Cl−, Br−, I−, F−, AcO−, H2PO4−, ClO4− and NO3− in an aqueous medium.

Charge transfer or biradicaloid character: assessing TD-DFT and SAC-CI for squarylium dye derivatives

Keeping in view to suggest one more class of molecules in order to make a choice and assessment of exchange–correlation (XC) functionals, symmetrical squarylium dye (SQ) derivatives have been considered and Le Baherss diagnostic indexes have been applied to study the electronic transition character of these molecular systems through TD-DFT and SAC-CI methods. Unlike calculated absorption using SAC-CI, the TD-DFT results do not match with experimental absorption data. However, the diagnostic indexes obtained with TD-DFT and SAC-CI are apparently similar for all methods. This indicates that care should be taken while choosing XC functionals and assessing the nature of electronic transitions of a specific class of molecules. The centroids of charges associated with the density increase and depletion regions are localized on the central C4 ring and carbonyl groups and with a small extension up to side aromatic substitution of the SQ dye derivative. Hence, the electronic transition occurring in this class of molecules is confined mainly within the central part of molecule. This is in contrast to donor–acceptor–donor type structure in which the charge depletion region is expected at side aromatic substitution of the molecule. The small values of calculated transferred charge (qCT) upon excitation lend support to the theory that the electronic transition in this class of molecules is not CT excitation. This is in agreement with our earlier finding that biradicaloid character and orbital interactions play a key role in their NIR absorption. Hence, highly correlated, single reference and a multi-determinant SAC-CI method is able to explain the nature of electronic excitations in these molecules rather than TD-DFT with various types of XC functionals.

Generating a three-dimensional non-fullerene electron acceptor by combining inexpensive spiro[fluorene-9,9′-xanthene] and cyanopyridone functionalities

Through the combination of cheaply synthesized structural fragments, spiro[fluorene-9,9′-xanthene] – otherwise termed low-cost spiro – and cyanopyridone, herein we report a new, three-dimensional, small molecule non-fullerene electron acceptor, (5Z,5′Z,5′′E,5′′′E)-5,5′,5′′,5′′′-((((S)-spiro[fluorene-9,9′-xanthene]-2,2′,7,7′-tetrayl)tetrakis(thiophene-5,2-diyl))tetrakis(methaneylylidene))tetrakis(4-methyl-1-octyl-2,6-dioxo-1,2,5,6-tetrahydropyridine-3-carbonitrile) [A1], which was synthesized for use in solution-processable bulk-heterojunction devices and was fully characterized by proton and carbon NMR spectroscopies together with elemental analysis. A1 was synthesized by a facile synthetic methodology using a Knoevenagel condensation reaction and was found to be highly soluble in a variety of common processing solvents such as chloroform and o-dichlorobenzene. Owing to its envisioned design, A1 displayed promising optoelectronic properties, and energy levels complementing those of the conventional donor polymers poly(3-hexylthiophene) [P3HT] and poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]-thieno[3,4-b]thiophenediyl}) [PTB7]. Given its energy levels, solubility and excellent film forming capability, A1 was used in bulk-heterojunction devices as an n-type semiconducting component. The device performances [D :  A 1 : 1.2 = 5.84% (P3HT); 7.21% (PTB7)] validated the design and use of A1 as an efficient non-fullerene acceptor.

The fluorescence detection of autophagosomes in live cells under starvation using core-substituted naphthalenediimide probes

A naphthalenediimide colorimetric pH sensor was designed, synthesised and employed for live cell applications. In DMSO : buffer solution, the NDI probe exhibits good pH selectivity and high photostability. We used a core-substituted naphthalenediimide (NDI-C) probe for the analysis of the autophagosomes. A new flow cytometric method was also developed for the analysis of cell population on the basis of intracellular pH.

A highly selective colorimetric Cys sensor based on core-substituted naphthalene diimides

This study presents the use of a core-substituted naphthalene diimide (NDI) probe for the selective sensing of cysteine (Cys). The UV-vis and colorimetric study showed that the NDI probe is highly selective towards Cys detection without any interference from other amino acids. We have also found that in the presence of Cys, the naked-eye color of receptor 1 changed from yellow to colourless. The sensing mechanism for Cys detection is based on the photoinduced electron transfer (PET) effect.

Proton Triggered Colorimetric and Fluorescence Response of a Novel Quinoxaline Compromising a Donor-Acceptor System

Quinoxaline-based novel acid-responsive probe Q1 was designed on the basis of a conjugated donor-acceptor (D-A) subunit. Q1 shows colorimetric and fluorometric changes through protonation and deprotonation in dichloromethane. With the addition of the trifluoroacetic acid (TFA), UV-vis absorption spectral changes in peak intensity of Q1 was observed. Moreover, the appearance of a new peaks at 284 nm 434 nm in absorption spectra with the addition of TFA indicating protonation of quinoxaline nitrogen and form Q1.H+ and Q1.2H+. The emission spectra display appearance of new emission peak at 515 nm. The optical property variations were supported by time resolved fluorescence studies. The energy band gap was calculated by employing cyclic voltammetry and density functional calculations. Upon addition of triethylamine (TEA) the fluorescence emission spectral changes of Q1 are found to be reversible. Q1 shows color changes from blue to green in basic and acidic medium, respectively. The paper strip test was developed for making Q1 a colorimetric and fluorometric indicator.

Effect of electron withdrawing groups on near infrared absorption of quinaldine-based squaraine dyes

The quinaldinium salt possessing electron withdrawing (-COOEt) groups was condensed with squaric acid giving the quinaldine based symmetrical squaraine dye. Effect of electron withdrawing group on near infrared absorption of the squaraine dye has been studied. Results showed that electron withdrawing group shifts bathochromically the absorption wavelength of squaraine dye by 31 nm when compared with the unsubstituted dye. Computational studies were performed in order to understand the charge transfer and red shift and later have been attributed to the increased biradicaloid character.