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71.
Haldar B Chakrabarty A Mallick A Mandal MC Das P Chattopadhyay N 《Langmuir : the ACS journal of surfaces and colloids》2006,22(8):3514-3520
Steady-state fluorescence measurements and isothermal titration calorimetric experiments have been performed to study the interaction between a telechelic polymer, pyrene-end-capped poly(ethylene oxide) (PYPY), and sodium alkyl sulfate surfactants having decyl, dodecyl, and tetradecyl hydrocarbon tails. Fluorometric results suggest polymer-surfactant interaction in the very low range of polymer concentrations. The relative variation in the excimer to monomer pyrene emission intensities with varying surfactant concentration reveals that initial addition of surfactant favors intramolecular preassociation until the surfactant molecules start binding with the ethylene oxide (EO) chain. With the growing number of surfactant aggregates along the EO chain, the association becomes hindered due to the polyelectrolyte effect. The results from microcalorimetric titrations in the low concentration range of PYPY solution (approximately 10(-6) M) with alkyl sulfates suggest two kinds of surfactant-polymer interactions, one with the polymer hydrophobic end groups and the other with the ethylene oxide backbone. The overall polymer-surfactant interaction starts at a much lower surfactant concentration for the hydrophobically modified polymers compared to that in the case of unsubstituted poly(ethylene oxide) homopolymer. From the experiments critical aggregation concentration values and the second critical concentration where free micelles start forming have been determined. An endeavor has been made to unveil the mechanism underlying the corresponding associations of the surfactants with the polymer. 相似文献
72.
Matranga C Bockrath B Chopra N Hinds BJ Andrews R 《Langmuir : the ACS journal of surfaces and colloids》2006,22(3):1235-1240
Raman spectroscopy has been used to investigate ethane, propane, and SF6 interactions with an aligned multiwalled carbon nanotube (MWNT) membrane. Pressures of 7.5-9.3 atm and temperatures of 293-333 K were examined for propane and SF6, whereas slightly lower temperatures (263-293 K) and pressures (6.7-7.5 atm) were used for ethane. Red-shifting and broadening is seen for the C-C stretching vibrations of the two hydrocarbons, as well as for the A1g symmetric vibration (nu1) of SF6. These spectral features indicate that the interaction between the gas and the nanotube membrane is capable of perturbing molecular vibrations and creating red-shifted features. Control experiments done on polycrystalline graphite and a polystyrene blank indicate that this spectral behavior is unique to gases interacting with the nanotubes in the membrane. 相似文献
73.
The reaction of allyl carbamates with activated olefins in the presence of Pd(PPh3)4 catalyst in THF proceeded smoothly at room temperature to give the corresponding beta,alpha-bisadducts, beta-amino-alpha-allylated products, in high yields. Not only highly activated olefins containing two cyano groups but also 2-cyano enones underwent facile aza-Michael addition--allylation with various allylic carbamates giving the corresponding products in high yields and with high diastereoselectivities. The stereochemistry of the singly formed product was confirmed with the help of X-ray crystallographic technique. It is an excellent method for creating beta-amino alpha-allyl ketones having two contiguous stereocenters: quaternary carbon adjacent to secondary amine carbon center. 相似文献
74.
Das P Mallick A Chakrabarty A Haldar B Chattopadhyay N 《The Journal of chemical physics》2006,125(4):44516
In continuation of our recent study on the steady state photophysics of a biologically active beta-carboline derivative, 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ), in the present article we have investigated the effect of nanocavity confinement on the excited state dynamics and rotational relaxation of the probe using picosecond time resolved fluorescence and fluorescence anisotropy techniques. The polarity dependent intramolecular charge transfer process is responsible for the remarkable sensitivity of this biological fluorophore in micellar environments. The fluorescence anisotropy decay of AODIQ incorporated inside the micelle is biexponential. The rotational motion of the probe was interpreted on the basis of a two step model consisting of a fast restricted rotation of the probe and a slow lateral diffusion of the probe in the micelle; both coupled to the overall rotation of the micelle. Experimental results reveal that micellar environment causes significant retardation of both the wobbling as well as the translational motion of the probe. 相似文献
75.
The palladium-catalyzed three-component beta-alkyl-alpha-allylation reaction of activated olefins has been achieved. For example, in the presence of 5 mol % of Pd(PPh3)4, the reaction of benzylidenemalononitrile 1a with Et3B and allyl acetate 2a in THF proceeded smoothly at 40 degrees C to give the corresponding beta-ethyl-alpha-allylated product 3a in 81% yield. 相似文献
76.
Nitin Wadnerkar Vijayanand Kalamse Ajay Chaudhari 《Journal of computational chemistry》2010,31(8):1656-1661
We report the gravimetric hydrogen uptake capacity of C2H4Sc complex and isoelectronic ions using Density Functional Theory. We predict that C2H4Sc+ can bind maximum seven hydrogen molecules in dihydrogen form giving gravimetric uptake capacity of 16.2 wt %, larger by about 2 and 4 wt % than the neutral and anion, respectively. We also found that the interaction of hydrogen molecules with C2H4Sc+ ion is characteristically different than that with neutral and anion. Vibrational spectroscopic study reveals that C2H4Sc and isoelectronic ions are quantum mechanically stable with their characteristic change in respective identified mode. The large gravimetric H2 uptake capacity of C2H4Sc+ is well above the target specified by Department of Energy (DOE) by 2015. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
77.
78.
Debosreeta Bose Deboleena Sarkar Nitin Chattopadhyay 《Photochemistry and photobiology》2010,86(3):538-544
In the present investigation, an attempt has been made to study the interaction of phenosafranin (PSF), a cationic phenazinium dye with the transport proteins, bovine serum albumin (BSA) and human serum albumin (HSA), employing steady-state and time-resolved fluorometric and circular dichroism (CD) techniques. The photophysical properties of the dye are altered on binding with the serum proteins. An explicit study with respect to the modification of the fluorescence and fluorescence anisotropy upon binding, effect of denaturant, fluorescence lifetime and CD measurements reveal that the dye binds to both BSA and HSA with almost the same affinity. Far-UV CD spectra indicate a decrease in the percentage of α-helicity only for BSA upon binding with the probe. Near-UV CD responses indicate an alteration in the tertiary structure of both the transport proteins because of binding. 相似文献
79.
Nitin T. Patil Vipender Singh Ashok Konala Anil Kumar Mutyala 《Tetrahedron letters》2010,51(11):1493-224
A process involving gold(I)-catalyzed formal carboamination of alkynes for the synthesis of C-3-substituted indoles has been developed. The procedure utilizes easily accessible starting materials such as 2-alkynylanilines and alkynols. A series of C-3-functionalized indoles are accessible by using this one-pot strategy. Mechanistically, the reaction involves three catalytic cycles and each of them is essentially catalyzed by a single metal catalyst, that is, Ph3PAuOTf. 相似文献
80.
Sachin V. Bhilare Amol R. Deorukhkar Nitin B. Darvatkar Meghana S. Rasalkar Manikrao M. Salunkhe 《Journal of molecular catalysis. A, Chemical》2007,270(1-2):123-126
Heteropoly acid tungstophosphoric acid (H3PW12O40) was found to be an excellent catalyst for the synthesis of symmetrical diaryl sulfoxides. The reaction was carried out in various organic solvents or ionic liquids and under solventfree condition. The reaction exhibited better results in terms of the yield and rate under solventfree condition. The catalyst was efficiently recovered from the reaction mixture and reused. The highlighting features of the present protocol are short reaction times, high yields of the products, ambient conditions, and simple workup. 相似文献