Bolin Chetia

H2O2 in WERSA: an efficient green protocol for ipso-hydroxylation of aryl/heteroarylboronic acid

A mild, green, economic and efficient protocol has been developed for ipso-hydroxylation of aryl/heteroarylboronic acids to phenols using 30% aqueous H2O2 as an oxidant and WERSA (water extract of rice straw ashes) as a neat reaction medium. All reactions were carried out without using metal, ligand, activator or hazardous organic solvent with excellent yield within a very short reaction time at room temperature. Therefore, this appears to be the cleanest and greenest alternative protocol for ipso-hydroxylation of aryl/heteroarylboronic acids.

Experimental and theoretical study of urea and thiourea based new colorimetric chemosensor for fluoride and acetate ions.

Two new anion receptors 1,1-(4-nitro-1,2-phenylene) bis(3-phenylurea) (1) and 1,1-(4-nitro-1,2-phenylene) bis(3-phenylthiourea) (2) have been reported here. The binding and colorimetric sensing properties of receptors 1 and 2 with different anions were investigated by naked-eye, (1)H-NMR and UV-Vis spectroscopy. They showed effective and selective binding with two biologically important anions F(-) and CH3COO(-), in presence of other anions, such as Cl(-), Br(-), I(-), NO2(-), ClO4(-), HSO4(-), H2PO4(-), N3(-), CN(-) in acetonitrile. The relative binding mode of fluoride and acetate anions towards receptors 1 and 2 were studied using density functional theory (DFT), in gas phase and in acetonitrile solvent. Computational studies revealed that receptor 1 formed complexes by two intermolecular hydrogen bonds while receptor 2 by three intermolecular hydrogen bonds. In addition, time dependent DFT (TD-DFT) calculations qualitatively match the experimental UV-Vis spectra.

Acetate recognition by 2,6-bis(2-benzimidazolyl)pyridine.

2,6-Bis(2-benzimidazolyl)pyridine, bbp, a simple tridentate ligand, is employed as a receptor for the recognition of anions. The binding of anionic guest species with bbp can be studied in short duration using UV/vis spectroscopy, fluorescence spectroscopy and (1)H NMR techniques at very low concentrations. The results obtained from the above spectroscopic techniques indicate that 2,6-bis(2-benzimidazolyl)pyridine is an efficient anion receptor providing chemical shift and optical modification based signals for the detection of acetate ions.

Green Nanosynthesis and Functionalization of Gold Nanoparticles as PTP 1B Inhibitors

Nanomedicine has emerged to become a frontier area of research. The interdisciplinary nature of nanoscale research inevitably leads to nanostructure fabrication and functionalization. Herein, we addressed on the potential of high therapeutic indexed Syzygium cumini seed to biofunctionalize gold nanoparticles. The aqueous seed extract of S. cumini acted as a reducing and capping agent in the formation of gold nanoparticles. Biofabricated gold nanoparticles was characterized using UV–vis spectrophotometry, TEM, SEM, EDAX, FTIR and XRD analysis. PTP 1B inhibitory activity of bioinspired gold nanoparticles was assessed using PTP 1B inhibition assay. Newly synthesized gold nanoparticles was found to possess high PTP 1B inhibitory potential. Furthermore, the newly synthesized nanoparticles not shown any genotoxicity during chromosomal studies indicates its high biocompatibility nature.

A Novel Benzimidazolyl-based Receptor for the recognition of Fluoride and Cyanide Anion

AbstractA novel benzimidazole based ligand (1) has been synthesized and studied its anion recognition properties. The binding of anion with 1 was studied using UV-Visible spectroscopy, fluorescence spectroscopy and 1H-NMR techniques at very low concentrations. The results obtained from the spectroscopic studies indicate that ligand 1 is an efficient anion receptor providing changes in chemical shift and optical signals for the detection of two most environmentally important anions, fluoride and cyanide.n Graphical AbstractA novel benzimidazole based ligand (1) was synthesized and reported for the detection of two most environmentally important anions, fluoride and cyanide. The binding of anion with 1 was studied using UV-Visible spectroscopy, fluorescence spectroscopy and 1H-NMR techniques at very low concentrations.n

On-water synthesis of phenols using biogenic Cu2O nanoparticles without using H2O2

In recent years the biogenic synthesis of metal oxide nanoparticles using natural resources has received significant attention due to their easy availability, low cost and environmentally benign protocol. In this study, Cu2O nanoparticles have been synthesised using Syzygium jambos (L.) Alston plant extracts without using toxic chemicals. The average size of the nanoparticles is 7.6xa0nm which found to have excellent catalytic activity in the ipso-hydroxylation of arylboronic acids without using H2O2. Mild reaction condition, excellent yield, easy separation and reusability of the catalyst are the advantages of this method.

Novel Isophthalohydrazide-cDB24C8 cryptand derivative for the selective recognition of fluoride ion: An experimental and DFT study

A highly selective and sensitive novel Isophthalohydrazide-cDB24C8 cryptand derivative was developed for fluoride recognition at a very low concentration of 2.31u202f×u202f10-10u202fM. The binding was established by UV-Vis, fluorescence and 1H NMR titration. The receptor formed very strong H-bonded complex with fluoride, furnished a sharp new UV-Vis absorption peak at 280u202fnm which was also supported by the DFT-study. The fluorescence emission spectra showed large quenching up to 79.13% upon addition of fluoride.

Biogenic CuFe2O4 magnetic nanoparticles as a green, reusable and excellent nanocatalyst for acetylation reactions under solvent-free conditions

A convenient green method has been developed for the synthesis of biogenic CuFe2O4 magnetic nanoparticles using tea extracts within a very short reaction time. The prepared nanoparticles with an average size of 8.78 nm have been used as an effective catalyst for the acetylation of various alcohols, phenols and amines in good to excellent yields under solvent-free conditions. The catalyst was characterized by XRD, XPS, VSM, SEM and TEM study. A magnetic study of the fresh and recycled catalyst after the fourth cycle was performed by VSM measurement. The main advantages of this protocol are simple biogenic synthesis of the catalyst, a reusable and heterogeneous catalytic system, and short reaction times with excellent yields.

Starch-templated bio-synthesis of gold nanoflowers for in vitro antimicrobial and anticancer activities

We describe an in situ method of synthesizing highly branched gold nanoflower (AuNFs) using aqueous seed extract of Syzygium cumini (L.) Skeels as reductant in the presence of 0.3% starch. Surprisingly, when the same reaction was carried out in the absence of starch or with starch at a lower concentration (0.15%), instead of flower-like morphology quasi-spherical or polyhedral nanoparticles (AuNPs) are obtained. The nanomaterials were extensively characterized by HRTEM, FESEM, UV–Vis, FTIR, XRD, XPS and TGA analysis. The biological activities of the materials were investigated for antimicrobial activities against four bacterial strains that include one Gram positive (Staphylococcus aureus MTCC 121), two Gram negative (Escherichia coli MTCC 40 and Pseudomonas aeruginosa MTCC 4673) and one fungi (Candida albicans MTCC 227). The nanoparticles functioned as effective antimicrobial and anti-biofilm agents against all the strains under study. Controlled study revealed that, the AuNFs showed improved efficacy over conventional polyhedral AuNPs against all the microbes under study which might be attributed to the larger surface-to-volume ratio of the nanoflowers. The AuNFs also showed effective in vitro anticancer activity against a human liver cancer cell line (HepG2) with no significant cytotoxicity. Our data suggest that the AuNFs can significantly reduce the cancer cell growth with IC50 value of 20xa0µg mL−1.

Chemical Composition and Antioxidant Activities of the Essential oil of Olax acuminata

Abstract In the present study, chemical composition and antioxidant activities of the essential oil of Olax acuminata was investigatd. The essential oils obtained by hydrodistillation was analyzed by gas chromatography-mass spectrometry (GC-MS). α-Terpineol (11.5 %) was the major component of the essential oil of O. acuminata. Further the antioxidant activity of the essential oil of the leaves of the plant was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide radical scavenging assay.