“Dial-In” Emission from a Unique Flexible Material with Polarization Tuneable Spectral Intensity

The development of organic photoluminescent materials, which show promising roles as catalysts, sensors, organic light-emitting diodes, logic gates, etc., is a major demand and challenge for the global scientific community. In this context, a photoclick polymerization method is adopted for the growth of a unique photoluminescent three-dimensional (3D) polymer film, E, as a model system that shows emission tunability over the range 350–650 nm against the excitation range 295–425 nm. The DFT analysis of energy calculations and π-stacking supports the spectroscopic observations for the material exhibiting a broad range of emission owing to newly formed chromophoric units within the film. Full polarization spectroscopic Mueller matrix studies were employed to extract and quantify the molecular orientational order of both the ground (excitation) and excited (emission) state anisotropies through a set of newly defined parameters, namely the fluorescence diattenuation and fluorescence polarizance. The information contained in the recorded fluorescence Mueller matrix of the organic polymer material provided a useful way to control the spectral intensity of emission by using pre- and post-selection of polarization states. The observation was based on the assumption that the longer lifetime of the excited dipolar orientation is attributed to the compactness of the film.     

Bi2O3/FAp,a sustainable catalyst for synthesis of dihydro-[1,2,4]triazolo[1,5-a]pyrimidine derivatives through green strategy

The bismuth loaded on fluorapatite (Bi₂O₃/FAp) proved to be an excellent catalyst for the synthesis of novel dihydro-[1,2,4]triazolo[1,5-a]pyrimidine derivatives via a three-component reaction involving the mixture of 1H-1,2,4-triazol-5-amine, ethyl cyanoacetate or ethyl acetoacetate, and different benzaldehydes in ethanol at room temperature. The catalyst material was characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, Fourier-transform infrared, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy techniques. The efficacy of Bi₂O₃/FAp as a heterogeneous catalyst was evaluated with the loading of different wt% of bismuth on FAp. The 2.5% bismuth on FAp performed extremely well as a catalyst with a high yield of products (92%–96%) in a short reaction time (25–35 min). The catalyst was recovered by simple filtration. It showed undiminished activity up to five runs. Simple work-up, room temperature reaction, short reaction time, high yields, no column chromatography, and good reusability of catalyst are the merits of the proposed protocol. In addition, this process offers 100% carbon efficiency and 98% atom economy with noteworthy fiscal and environmental benefits.     

Erratum to: Multiple Response Optimization of a HPLC Method for the Determination of Enantiomeric Purity of S-Ofloxacin

The aim of the study was to develop a new HPLC method for direct chiral separation of Ofloxacin enantiomers using polar non-aqueous mobile phase by application of response surface methodology. Rotatable central composite design (CCD) with eight factorial points, six axial points and six replications in central point was used to evaluate the influence of three independent variables (concentration of methanol, diethylamine and flow rate) on the output responses (capacity factor of first peak, tailing factors of both the enantiomers, resolution between the Ofloxacin enantiomers, retention time of the last peak and chromatographic optimization function). Further, CCD data were combined with multiple response optimization in order to obtain a set of optimal experimental conditions (% methanol/hexane/acetonitrile-43.33/10/46.62 (v/v), % acetic acid/diethylamine-0.4/0.2 and flow rate as 1.4 mL min⁻¹) leading to the most desirable compromise between resolution and analysis time. The method demonstrated good correlation between observed and predicted responses. The developed method was validated according to ICH guidelines and applied for quantitative analysis of two commercially available tablets Zenoflox (Ofloxacin) and Glevo (Levofloxacin). Good agreement was found between the assay results and the label claim of the marketed formulations by showing good %recovery and %CV. The study resulted in a better chromatographic system for the determination of Ofloxacin enantiomers.

     

Investigations on discotic liquid crystals

ABSTRACT

Discotic liquid crystals (DLCs) have reached from curiosity to commodity in a short span of time. Tremendous development has been observed in the field of DLCs in the past few years due to their vide-viewing display and unidirectional conducting properties. In this article, I present some aspects of research carried out by me and my collaborators on DLCs. This work was presented at the Asian Conference on Liquid Crystals (ACLC 2019) at Shenzhen, China during January 17–18, 2019.     

Investigating Two-Photon-Induced Fluorescence in Rhodamine-6G in Presence of Cetyl-Trimethyl-Ammonium-Bromide

We investigate the effect of cetyl-trimethyl-ammonium-bromides (CTAB) concentration on the fluorescence of Rhodamine-6G in water. This spectroscopic study of Rhodamine-6G in presence of CTAB was performed using two-photon-induced-fluorescence at 780 nm wavelength using high repetition rate femtosecond laser pulses. We report an increment of ～10 % in the fluorescence in accordance with ～12 % enhancement in the absorption intensity of the dye molecule around the critical micellar concentration. We discuss the possible mechanism for the enhancement in the two-photon fluorescence intensity and the importance of critical micellar concentration.     

Synthesis,characterization, and antimicrobial activity of new benzofuran derivatives

Russian Journal of General Chemistry - A novel series of (5-substituted-1-benzofuran-2-yl)(2,4-substituted phenyl)methanones (4a–4i) have been prepared by the Knoevenagel condensation of...