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41.
Manirul Islam Sanchita Mondal Paramita Mondal Anupam Singha Roy Dildar Hossain Manir Mobarak 《Transition Metal Chemistry》2011,36(1):1-11
Two copper complexes were synthesized from macroporous chloromethylated polystyrene beads. The first one was prepared by sequential
attachment of imidazole and copper acetate with chloromethylated polystyrene-divinyl benzene copolymer, and the second one
was prepared from 4-vinylpyridine and copper acetate with chloromethylated polystyrene-divinyl benzene copolymer. These catalysts
showed excellent catalytic activity in O-arylation reaction of aryl halides with phenol in dimethylsulfoxide using potassium
carbonate at 130 °C under open air conditions to give diaryl ethers in high yields. Less reactive aryl bromides and aryl chlorides
have also been shown to react with phenols to give good yields of the diaryl ethers. The effects of various parameters such
as solvent, catalyst from different copper salt and base on the reaction system were studied. The reaction is applicable to
a wide variety of substituted aryl halides and phenols with different steric and electronic properties. These catalysts were
recovered by simple filtration, and the reusability experiments showed that these catalysts can be used five times without
much loss in the catalytic activity. 相似文献
42.
Sengupta Arijit Deb Ashish Kumar Singha Gupta Nishesh Kumar Kumar Parveen Dasgupta Kinshuk Ali Sk. Musharaf 《Journal of Radioanalytical and Nuclear Chemistry》2018,315(2):331-340
Journal of Radioanalytical and Nuclear Chemistry - Herein, sorption of pentavalent neptunium from aqueous acidic solution was carried out onto 1st and 2nd generation of poly(amidoamine) dendrimer... 相似文献
43.
Sk. Manirul Islam Sumantra Paul Manir Mobarok Anupam Singha Roy Paramita Mondal 《Transition Metal Chemistry》2013,38(1):7-14
Polymer-anchored azo complexes of Cu(II) and Ni(II) were synthesized by the reaction of chloromethylated polystyrene, 3-aminophenol, and 1-nitroso-2-naphthol with the metal chlorides. The catalytic activities of these complexes were studied in the oxidation of various organic substrates including alkenes, alcohols, alkanes, and sulfides with 30 % aqueous hydrogen peroxide. The structures of both catalysts have been investigated by physiochemical methods. Both catalysts proved to be very stable and could be reused more than five times without significant loss of activity. Furthermore, these catalysts require very mild reaction conditions. 相似文献
44.
Manirul Islam Paramita Mondal Anupam Singha Roy Kazi Tuhina 《Transition Metal Chemistry》2010,35(4):491-499
A poly(3,6-dibenzaldimino N-vinyl carbazole) Pd(II) complex has been synthesized and characterized by physicochemical and
spectroscopic techniques. The complex was found to be highly active toward hydrogenation reactions of various organic substrates
under atmospheric pressure at ambient temperature. A tentative reaction mechanism is proposed on the basis of kinetic studies
and isolation of reactive intermediates. The catalyst shows good conversion rates, thermal stability and recyclability. 相似文献
45.
Haimanti Datta Anil K. Bhowmick Nikhil K. Singha 《Journal of polymer science. Part A, Polymer chemistry》2007,45(9):1661-1669
Atom transfer radical polymerization (ATRP) of ethyl acrylate (EA) was carried out using different initiators, CuBr or CuCl as catalyst in combination with different ligands e.g., 2,2′‐bipyridine (bpy) and N,N,N′,N″N″‐pentamethyl diethylenetriamine (PMDETA). Use of PMDETA as ligand resulted in faster polymerization rate (95% conversion in 15 min) than those using bipyridine (~58% conversion in 10.5 h). This is due to the lower reduction potential of copper‐amine than that of copper‐bpy complex, resulting in higher rates of activation of dormant halides. Use of ethylene carbonate as solvent lead to faster polymerization rate and better control in polymerization when compared with p‐xylene as solvent. The reaction temperature had a positive effect on polymerization rate and the optimum reaction temperature was found to be 90 °C. An apparent enthalpy of activation of ~85 kJ/mol was determined for the ATRP of ethyl acrylate, corresponding to an enthalpy of equilibrium of ~64 kJ/mol. By judicious choice of the reaction parameters it was possible to tailor the end group of the final polymer. MALDI‐TOF‐MS analysis and the chain extension experiment of poly(ethyl acrylate) (PEA) prepared using bpy as ligand showed the presence of ? Br as the end group. On the contrary, when PMDETA was used as the ligand, the mass spectra analysis showed hydrogen terminated polymer as the major species towards the end of polymerization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1661–1669, 2007 相似文献
46.
Anjan Biswas Abhijit Bandyopadhyay Nikhil K. Singha Anil K. Bhowmick 《Journal of polymer science. Part A, Polymer chemistry》2007,45(23):5529-5540
In this investigation, solution grafting of acrylic acid (AA) in presence of benzoyl peroxide (BPO) was carried out onto metallocene‐based “poly(ethylene‐octene) elastomers” (POE) as well as “poly(ethylene‐butene) elastomers” (PBE), to impart polarity on the non‐polar rubbery matrix and also to study the effects of crystallinity and pendant chain length on the “grafting percentage” and “percent gel yield” at optimized conditions for all the POE and PBE systems. Reaction parameters were optimized on the basis of the relative proportions of graft and gel formations obtained through %weight gain, Fourier Transform infrared spectroscopy and elemental analysis. The effect of grafting at its maximum level on various physico‐mechanical properties was also thoroughly investigated by using X‐ray diffraction (XRD), differential scanning calorimetry (DSC), mechanical, dynamic mechanical (DMTA), and thermogravimetric analysis (TGA) and the properties were correlated with the structure of the modified polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5529–5540, 2007 相似文献
47.
A genetic algorithm was used to control the photoluminesce-nce (PL) from GaAs(100). A spatial light modulator (SLM) used feedback from the emission to optimize the spectral phase profile of an ultrashort laser pulse. Most of the experiments were performed using a sine phase function to optimize the integrated PL spectrum over a specified wavelength range, with the amplitude and period of the phase function treated as genetic parameters. An order of magnitude increase in signal was achieved after only one generation, and an optimized waveform, consisting of three equally spaced pulses approximately 0.8 ps apart, was obtained after 15 generations. The effects of fluence, polarization, relative phase of the subpulses, and spectral range of the optimized PL were investigated. In addition, preliminary experiments were performed using the phases of individual pixels of the SLM as genetic variables. The PL spectrum is identified with recombination of electron-hole pairs in the L-valley of the Brillouin zone. Control is achieved by coherent manipulation of plasma electrons. It is proposed that hot electrons excite lattice phonons, which in turn scatter carriers into the L-valley. 相似文献
48.
49.
Subhankar Singha Dokyoung Kim Basab Roy Sunderraman Sambasivan Hyunsoo Moon Alla Sreenivasa Rao Jin Yong Kim Taiha Joo Jae Woo Park Young Min Rhee Taejun Wang Ki Hean Kim Youn Ho Shin Junyang Jung Kyo Han Ahn 《Chemical science》2015,6(7):4335-4342
The donor–acceptor (D–A) type dipolar fluorophores, an important class of luminescent dyes with two-photon absorption behaviour, generally emit strongly in organic solvents but poorly in aqueous media. To understand and enhance the poor emission behaviour of dipolar dyes in aqueous media, we undertake a rational approach that includes a systematic structure variation of the donor, amino substituent of acedan, an important two-photon dye. We identify several factors that influence the emission behaviour of the dipolar dyes in aqueous media through computational and photophysical studies on new acedan derivatives. As a result, we can make acedan dyes emit bright fluorescence under one- and two-photon excitation in aqueous media by suppressing the liable factors for poor emission: 1,3-allylic strain, rotational freedom, and hydrogen bonding with water. We also validate that these findings can be generally extended to other dipolar fluorophores, as demonstrated for naphthalimide, coumarin and (4-nitro-2,1,3-benzoxadiazol-7-yl)amine (NBD) dyes. The new acedan and naphthalimide dyes thus allow us to obtain much brighter two-photon fluorescent images in cells and tissues than in their conventional forms. As an application of these findings, a thiol probe is synthesized based on a new naphthalimide dye, which shows greatly enhanced fluorescence from the widely used N,N-dimethyl analogue. The results disclosed here provide essential guidelines for the development of efficient dipolar dyes and fluorescence probes for studying biological systems, particularly by two-photon microscopy. 相似文献
50.
Chakraborty B Roy AS Dasgupta S Basu S 《The journal of physical chemistry. A》2010,114(51):13313-13325
Conventional spectroscopic tools such as absorption, fluorescence, and circular dichroism spectroscopy used in the study of photoinduced drug-protein interactions can yield useful information about ground-state and excited-state phenomena. However, photoinduced electron transfer (PET) may be a possible phenomenon in the drug-protein interaction, which may go unnoticed if only conventional spectroscopic observations are taken into account. Laser flash photolysis coupled with an external magnetic field can be utilized to confirm the occurrence of PET and authenticate the spin states of the radicals/radical ions formed. In the study of interaction of the model protein human serum albumin (HSA) with acridine derivatives, acridine yellow (AY) and proflavin (PF(+)), conventional spectroscopic tools along with docking study have been used to decipher the binding mechanism, and laser flash photolysis technique with an associated magnetic field (MF) has been used to explore PET. The results of fluorescence study indicate that fluorescence resonance energy transfer takes place from the protein to the acridine-based drugs. Docking study unveils the crucial role of Ser 232 residue of HSA in explaining the differential behavior of the two drugs towards the model protein. Laser flash photolysis experiments help to identify the radicals/radical ions formed in the due course of PET (PF(?), AY(?-), TrpH(?+), Trp(?)), and the application of an external MF has been used to characterize their initial spin-state. Owing to its distance dependence, MF effect gives an idea about the proximity of the radicals/radical ions during interaction in the system and also helps to elucidate the reaction mechanisms. A prominent MF effect is observed in homogeneous buffer medium owing to the pseudoconfinement of the radicals/radical ions provided by the complex structure of the protein. 相似文献