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981.
C. Robert Lucas Kamala Mitra Subhendu Biswas Shyamal Kumar Chattopadhyay Bibhutosh Adhikary 《Transition Metal Chemistry》2005,30(2):185-190
A series of mononuclear MnII and MnIV complexes of general formulae [MnL2(NCS)2] (1a–1d) and [Mn(L)2(NCS)2] (2a–2c) have been prepared where L are Schiff bases obtained by the condensation of pyridine-2-aldehyde with para-alkyl-substituted aniline, and L are the corresponding amide ligands. The room temperature magnetic susceptibility data of (1a–1d) indicate that MnII is in a high spin state. The cyclic voltammograms of (1a–1d) exhibit a one-electron quasi-reversible MnIIMnIII oxidation. A linear correlation has been found when E0[MnIII/MnII] is plotted against Hammett p parameters. X-ray crystallographic data of (1b) shows that the central MnII ion adopts a distorted octahedral geometry with six different Mn–N distances. Upon oxidation of MnII complexes (1b–1d) by H2O2, the corresponding MnIV complexes (2a–2c) were obtained, and the Schiff base ligands were oxidized to the corresponding amides. The lowest energy LMCT bands of these MnIV complexes correlate linearly with Hammett p parameters. The redox behavior of the MnIV complexes has been investigated by cyclic voltammetry. E.p.r. spectra of the MnII and MnIV complexes are also reported. 相似文献
982.
Sorption of51Cr(VI) by MnO2 has been studied as a function of pH and ionic concentration in the presence of certain added cations and anions. The findings are explained in the light of deprotonation/hydroxyl ion association reaction on oxide surface and its subsequent interaction with the tracer. Infrared spectroscopy has shown the chemical interaction of Cr(VI) on the surface of MnO2. The influence of certain interfering ions has been shown on the sorption of51Cr(VI) on MnO2 surface. An attempt has been made to concentrate traces of51Cr under optimum experimental conditions. The experimental observation shows that the activity sorbed under specified conditions can be recovered appreciably by leaching the pre-adsorbed carrier. 相似文献
983.
Summary Application of hexamethylphosphoramide (HMPA) in the iron(III)-thiocyanate system gives a simple, sensitive and highly selective method for the spectrophotometric determination of Fe(III) in the organic phase (CHCl3). The color is stable for more than 24 hours in CHCl3. The system obeys Beer's law for 7g Fe/ml and the optimum concentration range is found to be 0.5–5g/ml. The molar absorptivity of 1.33×104 l·mole–1·cm–1, and Sandell's sensitivity is 0.0044/cm2 at 460 nm The composition of Fe(III) to thiocyanate is found to be 13 in the presence of HMPA in CHCl3. The method is free from interferences of many anions and cations. The method has been used to determine iron in bauxite ore.
Flüssig-flüssig-Extraktion von Eisenrhodanid nach Zusatz von Hexatnethyl-pbosphoramid: Direkte spektrophotometrische Bestimmung in der organischen Phase
Zusammenfassung Der Zusatz von Hexamethylphosphoramid (HMPA) zu Eisen(III)-Thiocyanat führt zu einer einfachen, empfindlichen und sehr selektiven Methode der spektrophotometrischen Bestimmung von Fe(III) in organischer Phase (CHCl3). Die Farbe bleibt in Chloroform mehr als 24 Stunden beständig. Das System entspricht dem Beerschen Gesetz unterhalb 7g Fe/ml. Das Konzentrationsoptimum liegt zwischen 0,5 und 5g/ml. Die molare Extinktion beträgt 1,33·104 l·Mol–1·cm–1, die Empfindlichkeit nach Sandell 0,0044g/cm2 bei 460 nm. Das Verhältnis Fe(III): Rhodanid in CHCl3 ist 13 in Gegenwart von HMPA. Die Methode wird von vielen Anionen und Kationen nicht gestört. Sie wurde zur Bestimmung von Eisen in Bauxit verwendet.相似文献
984.
One-photon absorption coefficients of InSb and GaAs are calculated using the first order perturbation theory assuming a two band model in which the interband energy difference is given by The results obtained are in much better agreement with the experimental data than the results of first order perturbation calculations using parabolic bands. 相似文献
985.
Sk. F. Ahmed S. Khan P. K. Ghosh M. K. Mitra K. K. Chattopadhyay 《Journal of Sol-Gel Science and Technology》2006,39(3):241-247
Al doped SnO2 thin films have been synthesized by a sol-gel dip coating technique with different percentages of Al on glass and silicon
substrates. X-ray diffraction studies confirmed the proper phase formation in the films and atomic percentage of aluminium
doping in the films was obtained by energy dispersive X-ray studies. SEM studies showed the particle sizes lying in the range
100–150 nm for the undoped films and it decreased with increase of Al doping. Optical transmittance spectra of the films showed
high transparency (∼80%) in the visible region and the transparency increases with the increase of Al doping in the films.
The direct allowed bandgap of the films have been measured for different Al concentration and they lie within the range of
3.87–4.21 eV. FTIR studies depicted the presence of Sn–O, Al–O, bonding within the films. The room temperature electrical
conductivities of the films are obtained in the range of 0.21 S cm−1 to 1.36 S cm−1 for variation of Al doping in the films 2.31–18.56%. Room temperature Seebeck coefficients, SRT of the films were found in the range +56.0 μVK−1 to −23.3 μVK−1 for variation of Al doping in the films 18.56–8.16%. It is observed that the Seebeck coefficient changes its sign at 12.05%
of Al in the films indicating that below 12.05% of Al doping, SnO2:Al behaves as an n-type material and above this percentage it is a p-type material. 相似文献
986.
The kinetics of the anation reaction of cis-diaquo-bis-oxalatochromate(III) ion by DL-alanine has been studied spectrophotometrically
in the pH range 3.8 to 7.3, where DL-alanine remains in zwitterionic form. A second-order rate law has been established. Reaction
rates in three different ethanol-water mixtures were measured. In each solvent medium the anation rate is higher as compared
to water exchange reaction at a particular temperature. The activation parameters (gDH# and ΔS#) in different ethanol-water mixtures were obtained from Eyring plots. ΔG#(ΔH# −TΔS
#) values were calculated in each solvent medium and compared with that of the isotopic water exchange process. A reaction
mechanism involving theS
N2 path has been suggested. 相似文献
987.
Physicochemical investigations of microemulsification of eucalyptus oil and water using mixed surfactants (AOT+Brij-35) and butanol 总被引:3,自引:0,他引:3
Microemulsification of a vegetable oil (eucalyptus) with single and mixed surfactants (AOT and Brij-35), cosurfactant of different lipophilicities (isomers of butanol), and water were studied at different surfactant and cosurfactant mixing ratios. The phase diagrams of the quaternary systems were constructed using unfolded and folded tetrahedron, wherein the phase characteristics of different ternary systems can be underlined. The microemulsion zone was found to be dependent upon the mixing ratios of surfactant and cosurfactant; the largest microemulsion zone was formed with 1:1 (w/w) S:CS. The effects of temperature and additives (NaCl, urea, glucose, and bile salts of different concentrations) on the phase behavior were examined. The mixed microemulsion system showed temperature insensitivity, whereas the Brij-35 (single) stabilized system exhibited a smaller microemulsion zone at elevated temperature. NaCl and glucose increased the microemulsion zone up to a certain concentration, beyond which the microemulsion zones were decreased. These additives decreased the microemulsion zones as temperature was increased. The effect of urea on microemulsion zone was found to be insignificant even at the concentration 3.0 mol dm(-3). Little effect on microemulsion zone was shown by NaC (sodium cholate) at 0.25 and 0.5 mol dm(-3) at different temperatures. The conductance of the single (AOT) and mixed microemulsion system (AOT+Brij-35) depends upon the water content and mixing ratios of the surfactants, and a steep rise in conductance was observed at equal weight percentages of oil and water. Viscosities for both single (AOT) and mixed (AOT+Brij-35) surfactant systems passed through maxima at equal oil and water regions showing structural transition. The viscosities for microemulsion systems increased with increasing Brij-35 content in the AOT+Brij-35 blend. Conductances and viscosities of different monophasic compositions in the absence and presence of additives (NaCl and NaC) were measured at different temperatures. The activation energy of conduction (DeltaE(cond)( *)) and the activation enthalpy for viscous flow (DeltaH(vis)( *)) were evaluated. It was found that both DeltaE(cond)( *) and DeltaH(vis)( *) were a function of the nature of the dispersion medium. Considering the phase separation point of maximum solubility, the free energy of dissolution of water or oil (DeltaG(s)(0)) at the microdispersed state in amphiphile medium was estimated and found to be a function of surfactant composition. 相似文献
988.
Effect of temperature and salt on the phase behavior of nonionic and mixed nonionic-ionic microemulsions with fish-tail diagrams 总被引:1,自引:0,他引:1
The phase behavior of Brij-56/1-butanol/n-heptane/water is investigated at 30 degrees C with alpha [weight fraction of oil in (oil+water)]=0.5, wherein a 2-->3-->2 phase transition occurs with increasing W1 (weight fraction of 1-butanol in total amphiphile) at low X (weight fraction of both the amphiphiles in the mixture) and a 2-->1-->2 phase transition occurs at higher X. Addition of an ionic surfactant, sodium dodecylbenzene sulfonate, destroys the three-phase body and decreases the solubilization capacity of the system at different delta (weight fraction of ionic surfactant in total surfactant). A three-phase body appears at alpha=0.25, but not at alpha=0.75 for the single system. No three-phase body appears with the mixed system at either alpha value. Increased temperature increases the solubilization capacity of the Brij-56 system; on the other hand, a negligible effect of temperature on the Brij-56/SDBS mixed system has been observed. Addition of salt (NaCl) produces a three-phase body for both single and mixed systems and increases their solubilization capacities. The monomeric solubility of 1-butanol in oil (S1) and at the interface (S1s) has been calculated using the equation hydrophile-lipophile balance plane for both singles- and mixed-surfactant systems. These parameters have been utilized to explain the increase in solubilization capacity of these systems in the presence of NaCl. 相似文献
989.
Phase behaviors of AOT/heptane (Hp)/formamide (FA), ethylene glycol (EG), propylene glycol (PG), triethylene glycol (TEG) and glycerol (GLY) have been investigated in the absence and presence of a nonionic surfactant, polyoxyethylene(2) cetyl ether (Brij-52) at 303 K. The phase characteristics of (AOT+Brij-52)/Hp/(EG or PG or TEG) have been found to be different from that of AOT/Hp/FA systems in respect of both the area of monophasic domain and the appearance of other mesophases. The area of monophasic domain of (AOT+Brij-52)/Hp/EG depends on the content of Brij-52 (X
Brij-52) and shows a maximum at X
Brij-52=0.4. A negligible effect on the area of the monophasic domain has been shown by more hydrophobic surfactants, polyoxyethylene(2) stearyl ether (Brij-72) and polyoxyethylene(2) oleyl ether (Brij-92). The effect of oils (dodecane and hexadecane) on the mixed systems stabilized by (AOT+Brij-52) in EG has been investigated. The area of monophasic domain has been found to be dependent on the type of nonaqueous solvents and follows the order GLY>EG>PG>TG. A systematic investigation on the measurement of phase volumes of mixed surfactant systems [AOT+nonionic surfactant(s)] stabilized in oils of different chain lengths (heptane, dodecane and hexadecane) and polar solvent (EG) has been carried out at different compositions of the ingredients to identify the phase transitions of these systems as a function of X
Brij-52. The threshold point of phase transition (both W I→W IV and W IV→W II transitions) has been found to be a function of the configuration of added nonionic surfactant, nature of the polar solvent and oil. The conversion of the initial oil/EG droplets into EG/oil droplets with increasing X
nonionic has been facilitated for hydrophobic surfactants polyoxyethylene(4) lauryl ether (Brij-30), Brij-52, and Brij-72 in comparison to the hydrophilic surfactants polyoxyethylene(10) cetyl ether (Brij-56) and polyoxyethylene(20) cetyl ether (Brij-58). 相似文献
990.
Parimal Kundu Samiran Mitra Sonjay Kumar Dilip Banerjee Ranga Lal Bhattacharya 《Transition Metal Chemistry》1995,20(5):417-422
Summary Double complex salts containing cationic CuII having cyclic ligand piperazine (pipz), N-methylpiperazine (mpipz) and N,N-dimethylpiperazine (dmpipz) and hexacyanoferrate(III) ion have been synthesized and characterized by elemental analyses, i.r. and electronic spectra, and magnetic moment measurements. Mössbauer spectra at room temperature and at 80 K, were recorded in order to evaluate the metal-metal charge transfer and the impact of the cyclic ligand present in cationic moiety of the double complex salt upon the Mössbauer spectra of the hexacyanoferrate(III) ion. Evidence for metal-metal charge transfer is supported by electronic spectra and magnetic susceptibilities. Variable temperature e.p.r. spectra were recorded in order to determine the distortion of crystal system. Thermally induced stereochemical studies have been carried out with the help of i.r. spectral data. Kinetics of thermochemical reactions have also been studied. Activation energies (E
infa
sup*
) and inception temperatures for the thermochemical reactions show the order of stability of the double complex salts follows the trend: dmpipz > mpipz > pipz, which indicates that the + I effect is more pronounced than steric effect. 相似文献