The development of phosphinoamine–Pd(II)–imidazole complexes: implications in room‐temperature Suzuki–Miyaura cross‐coupling reaction

The reaction of N‐methylimidazole (N‐MeIm) and N‐butylimidazole (N‐BuIm) with the complexes [PdCl₂(PPh₂py–P,N)] and [PdCl₂(PPh₂Etpy–P,N)] in the presence of NH₄PF₆ under N₂ at room temperature afforded four new cationic Pd(II) complexes [PdCl(PPh₂py–P,N)(N‐MeIm)](PF₆) ( 1 ), [PdCl(PPh₂py–P,N)(N‐BuIm)](PF₆) ( 2 ), [PdCl(PPh₂Etpy–P,N)(N‐MeIm)](PF₆) ( 4 ) and [PdCl(PPh₂Etpy‐P,N)(N‐BuIm)](PF₆) ( 5 ) in good yields, where PPh₂py is 2‐(diphenylphosphino)pyridine and PPh₂Etpy is 2‐{2‐(diphenylphosphino)ethyl}pyridine). The complexes were fully characterized. The catalytic activities of these complexes were investigated for Suzuki–Miyaura cross‐coupling reactions at room temperature. Complex 2 exhibited excellent activity compared to other analogs. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and Characterization of Oxygen Vacancy Induced Narrow Bandgap Tungsten Oxide (WO3−x) Nanoparticles by Plasma Discharge in Liquid and Its Photocatalytic Activity

Plasma Chemistry and Plasma Processing - Narrow bandgap tungsten oxide (WO3?x) nanoparticles have been synthesized by single-step plasma discharge in deionized water between two vertically...     

Effect of Association of Curcumin with Chitosan in Presence of TX 100 on Its Degradation

The binding of curcumin with chitosan in the presence of nonionic surfactant, iso-octylphenoxy-polyethoxy-ethanol (Triton X-100) and its stability in such systems have been investigated by monitoring the changes in the absorption spectra at physiological pH (7.4). It was observed that curcumin binds to chitosan more than 10 times stronger in presence of TX 100 at the experimental condition. From spectrophotometric analysis of the kinetics of degradation of the dye, it was observed that the yield of suppression of degradation of curcumin by chitosan increases by 33.5% in the presence of TX 100 than alone. The interaction of the dye with chitosan has been found to be exothermic and driven by hydrophobic interactions, hydrogen bond formation, and electrostatic interactions.     

Congruences for ℓ-regular overpartition for ℓ ∈ {5, 6, 8}

Let A? _?(n) denote the number of overpartitions of a non-negative integer n with no part divisible by ?, where ? is a positive integer. In this paper, we prove infinite family of congruences for A? ₅(n) modulo 4, A? ₆(n) modulo 3, and A? ₈(n) modulo 4. In the process, we also prove some other congruences.     

Synthesis,Characterization, Properties,and Novel Applications of Fluorescent Nanodiamonds

In the last few years, fluorescent nanodiamonds (FNDs)  have been developed significantly as a new member in the nanocarbon family. The surface of FNDs is embedded with some crystallographic defects containing color centres which surmount the properties of other fluorochromes including up conversion and down conversion nanoparticles, quantum dots, nano tubes, fullerenes, organic dyes, silica etc. Some of the intriguing properties like inevitable photostability, inherent bio-compatibility, outstanding optical and robust mechanical properties, excellent magnetic field, and electric field sensing potentiality make FNDs appealing to some benevolent applications in numerous fields like bio-imaging, delivering drugs, fighting cancer, spin electronics, imaging of magnetic structure at nanoscale and as promising nanometric temperature sensor. The structure of FNDs has certain point defects on the surface among which negatively charged nitrogen vacancy centre (NV^?) is the most investigated color centre. The production of NV^? fluorescence nanodiamonds is the most challenging task as substitution of carbon atoms is required to create vacancies by causing irradiation from an electron beam which is followed by high temperature annealing. Thus, this review points out the relative advantages of FNDs containing negatively charged nitrogen vacancy centres produced from HPHT method or CVD method with those nanodiamonds produced through detonation process or pulsed laser ablation (PLA) method. The steps involved in the fabrication of FNDs are described along with the major challenges and struggles underwent during the process in this review. This review also summarizes the recent developments made in the functionalization and applications predominantly made in the field of biological science and it is understood that depending on the defect color centres they can exhibit different emitted wavelengths ranging from UV–visible to near infrared with broad or narrow bandwidths. This review also highlights some of the fluorescent NDs that emit stable and strong red or green photoluminescence from the defect centers of NV^? which are implanted in the crystal lattice. This critical and extensive review will be useful for the further progress in this futuristic field of FNDs.

     

Selective oxidation of organic sulfides by mononuclear and dinuclear peroxotungsten(VI) complexes

Clean conversion of a variety of sulfides and dibenzothiophene (DBT) to the corresponding sulfoxide or sulfone could be achieved in high yields at room temperature using mononuclear as well as dinuclear diperoxo complexes of tungsten as oxidants, by a variation of reaction conditions. The compounds could also effectively catalyze oxidation of sulfides by H₂O₂ to selectively yield sulfone with reasonably good turnover frequency (TOF).     

Focal field computation of an arbitrarily polarized beam using fast Fourier transforms

In this work the vectorial diffraction theory of Richards and Wolf is extended to compute the focal field components of an arbitrarily polarized beam using fast Fourier transform (FFT) operations. Here the arbitrarily polarized pupil function is written as the vector sum of two mutually perpendicularly polarized pupil functions. The FFT based focal field expressions are particularly useful to compute the focal field components of pupil functions without a simple analytical form. We have then applied these expressions to simulate the effects of Zernike mode aberrations on the point spread functions of a number of important cylindrical-vector beam profiles such as radially and azimuthally polarized and helical light beams.     

Phosphine-free Suzuki cross-coupling reaction: a mild and selective method for the carbon–carbon bond formation in aqueous tea extract

A mild and selective protocol has been developed for the palladium-catalyzed phosphine-free Suzuki cross-coupling reaction of aryl bromides with arylboronic acids in aqueous tea extract at room temperature. It is noteworthy that the aqueous tea extract plays an important role in the reaction, and various functional groups are tolerated under the optimized conditions. The reactions proceeded with very good chemoselectivity in favor of the bromo instead of the chloro group even at higher temperatures. Furthermore, this protocol could be applied to the cross-coupling of 4-bromoindole without protecting the base sensitive amine group with arylboronic acids in moderate to excellent yields.     

Studies on 2,1-benzisoxazoles. Behaviour towards electrophilic substitution and cycloaddition reactions

The behaviour of 2,1-benzisoxazoles (anthranils) towards electrophilic substitutions has been studied. Nitration of 5-chloro-2,1-benzisoxazole (VII) exclusively gives 4-nitro-5-chloro-2,1-benzisoxazole (XII). However, 5-chloro-3-phenyl-2,1-benzisoxazole (VIII) gives dinitrated products XIII, one nitro group entering at position C₇ instead of C₄ of the carbocyclic ring and the other at the 4′ position of the 3-aryl ring. When 6-nitro-3-carbalkoxy-2,1-benzisoxazoles (X and XI) are nitrated, 4-nitroisomers XV and XVI are obtained exclusively. The substituents already present in the carbocyclic ring exert decisive directing influence. While the parent 2,1-benzisoxazole (Ia) fails to react with dimethyl acetylenedicarboxylate, 6-nitro-2,1-benzisoxazole (XVII) and 5-chloro-2,1-benzisoxazole (VII) react to give 1,4-cycloadducts XIX and XX, respectively. These results suggest that 2,1-benzisoxazoles possess benzenoid as well as ortho-quinonoid character.     

A facile synthesis of 2,4,8,10-tetrahalo-6,12-diaryldibenzo[b,f][1,5]diazocines

3,5-Dihalo-2-aminobenzophenones 2 on prolonged reflux in dry pyridine gave 2,4,8,10-tetrahalo-6,12- diaryldibenzo[b,f][1,5]diazocines 3 in high yields. Attempted condensation of 2 with glycine ester hydrochloride under identical reaction conditions failed to afford 1,4-benzodiazepines.