Calix[4]pyrrole macrocycle: Extraction of fluoride anions from aqueous media

Solid-phase extraction of fluoride anions by calixpyrrole macrocycle (CP) from aqueous media has been studied using the batch method. Various significant extraction parameters like initial concentration of the anion, extraction time, concentration of the calixpyrrole, pH and temperature were evaluated. Langmuir, Freundlichand, Dubinin-Redushkevish (D-R) isotherms and coefficients were used to analyze the equilibrium data. The amount of fluoride anion extracted per unit of the CP was found to be 0.40 mg/g at 298 K from 19 mg/L aqueous solution of fluoride anions. The mean free energy calculated from D-R model for the removal of fluoride anions by the CP was found to be 10.0 kJ/mol, indicating that chemisorption is involved in the extraction process. The data were also fitted to kinetic models such as pseudo first order and pseudo second order. The removal of fluoride anions increased with increasing temperature indicating the endothermic nature of the extraction process. The present method has been compared with the previous methods

Solvatochromic absorption and fluorescence studies of adenine, thymine and uracil thio-derived acyclonucleosides

Adenine, thymine and uracil thio-derived acyclonucleosides were synthesized and characterized by UV-Vis, FT-IR, 1H and 13C NMR spectroscopic techniques. The photophysical properties of the derivatives were evaluated in solvents with diverse polarities and at various pH values. The solvent dependent absorbance and emission spectral shifts were analysed using physical parameters of the selected solvents. The regression and correlation coefficients were calculated using multiple regression techniques. The fitting coefficients gave an estimate of the contribution of each interaction to the total spectral shift in various solutions. Multiple linear regression studies, Kamlet-Taft equation and stokes shift correlation with orientation polarizability provide valuable information concerning spectroscopic characteristics of the studied molecules

Lead uptake by new silica-carbon nanoparticles

Silica-carbon nanoparticles (SCNP) were prepared from sonication of silica and anthracene. The size of homogenous nanoparticle is around 5-20 nm confirmed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). SEM analysis indicated surface porosity. SCNP were used to remove lead ions (Pb(II)) from aqueous solutions. Adsorption isotherm of Pb(II) on SCNP was well fitted in terms of the Freundlich and Langmuir models. The maximum adsorption capacity of SCNP for Pb(II) was found to be 385 mg/g (1.86 mmol/g) in batch experiment. Thermodynamic studies indicated that sorption process of lead onto SCNP was spontaneous and exothermic. A pseudo-second order model has been employed in order to describe the kinetic adsorption processes, and the thermodynamic activation parameters were calculated. In a column studies, qy the Yan adsorption capacity of SCNP for Pb(II) was found to be 130.66 mg/g (0.63 mmol/g)

Synthesis, characterizations and reactions of low valent complexes of molybdenum containing (bis(2-diphenylphosphinoethyl)phenyl-phosphine), and, A nitrogen fixation approach

High energy electron rich molybdenum phosphine complexes were synthesised by the reduction of (Mo(TRI)Cl\sb3) in THF with sodium amalgam in the presence of various ligands: arenes, cyclopentadiene, indene, dinitrogen, phosphines and phosphites; (TRI is (Bis(2-diphenylphosphinoethyl)phenylphosphine). The products are: i, (Mo(\eta\sp6-arene)(TRI)), (arene = C\rm\sb6H\sb6, C\rm\sb6H\sb5OCH\sb3, C\rm\sb6H\sb5CH\sb3, C\rm\sb{10}H\sb8 or PPh\sb3); ii, (Mo(\eta\sp5-C\rm\sb5H\sb5)(TRI)H); iii, (Mo(\eta\sp5-C\rm\sb9H\sb7)(TRI)H); iv, fac- (Mo(N\sb2)(TRI)(PMe\sb3)\sb2); v, (Mo(N\sb2)(\eta\sp3-TRI)(\eta\sp2-TRI)); vi, mer- (Mo(TRI)(P(OR)\sb3)\sb3), (R = Me or Et). When THF solvent was used and in the abscence of added ligands, the products are (Mo(TRI)(THF)\sb3) under argon and $\{$Mo(N\sb2)(TRI)(THF)$\}$x under dinitrogen. Heating fac- (Mo(N\sb2)(TRI)(PPhMe\sb2)\sb2) in THF with ethylene produced trans- (Mo(CH\rm\sb2CH\sb2)\sb2(TRI)(PPhMe\sb2). Heating trans- (Mo(N\rm\sb2)\sb2(TRI)(PPh\sb3)) in THF formed (Mo(\eta\sp6-PhPPh\sb2)(TRI)) by rearrangement of $\sigma$- to \eta\sp6-bonded PPh\sb3. Reaction of (Mo(\eta\sp6-arene)(TRI)) with strong acid formed (Mo(\eta\sp6-C\rm\sb6H\sb6)(TRI)H) \sp+ and (Mo(\eta\sp6-arene)(TRI)(H\sb2\rbrack\sp{2+}. The hydride complex (Mo(\eta\sp5-C\rm\sb5H\sb5)(TRI)H) was also prepared by heating fac- (Mo(N\sb2)(TRI)(PMe\sb3)\sb2) with cyclopentadiene in heptane. The hydride complex reacted with CDCl\sb3 forming (Mo(\eta\sp5-C\rm\sb5H\sb5)-(TRI)Cl) and (Mo(\eta\sp5-C\rm\sb5H\sb5)(TRI)(CCl\sb3)) (Mass spectra: m + 1/z = 732 and 818 respectively). Mer- (Mo(TRI)(P(OR)\sb3)\sb3) isomerizes to fac- (Mo(TRI)(P(OR)\sb3)\sb3) both thermally and photochemically. Both Mer- (Mo(TRI)(P(OR)\sb3)\sb3) and (Mo(\eta\sp6-arene)(TRI)) exhibit two oxidation waves in the cyclic voltammograms in THF. The first oxidation is reversible but the second oxidation is pseudoreversible. The reaction of HBr with trans- (Mo(N\sb2)\sb2(dppe)(PPh\rm\sb2Me)\sb2) in THF formed (Mo(NNH\sb2)(THF)(dppe)(PPh\sb2Me)Br) Br, (Mo(NNH\sb2)(dppe)-(PPh\rm\sb2Me)\sb2Br) Br and (Mo(NNH\sb2)(dppe)(PPh\rm\sb2Me)Br\sb2). The reaction of (Mo(NNH\sb2)(dppe)(PPh\rm\sb2Me)(Br\sb2) with pyridine formed the diamagnetic (Mo(NNH\sb2(dppe)(PPh\rm\sb2Me(C\sb5H\sb5N)Br) Br. In contrast, the reactions of (Mo(NNH\sb2)(dppe)(PPh\rm\sb2Me)Br\sb2) or (Mo(NNH\sb2)(dppe)-(PPh\rm\sb2Me)\sb2Br) Br with pyrazine formed the purple paramagnetic (Mo(NNH\sb2)(dppe)(PPh\rm\sb2Me)(C\sb4H\sb4N\sb2)Br) Br, (UV, $\lambda$ = 572 nm). A mechanism for ammonia and hydrazine production was proposed. It involves a series of electronation and protonation steps. Finally, the reactions of fac- (Mo(N\sb2)(TRI)(PMe\sb3)\sb2) and fac- (Mo(N\sb2)(TRI)(dppm)) produced the corresponding carbon dioxide complexes, IR (KBr), v(CO\sb2) = 1758.80 and 1779.98 cm\sp{-1} respectively