Enhancement of two-photon absorption cross-section in macrocyclic thiophenes with cavities in the nanometer regime

The linear and nonlinear optical properties of two thiophene-based cyclic molecules have been investigated. These molecules represent nanometer sized cavities which may be useful for novel photonic devices. By virtue of long-range interactions, these chromophores serve as novel architectures for enhanced two-photon absorption (TPA) properties. Measurements of the different size ring structures showed a 550% increase in the TPA cross-section for the larger macrocycle. Electronic structure calculations have suggested an increase in coupling of the excited states in these systems as the ring size is increased. Measurements of the ultrafast transient absorption and fluorescence were carried out with these systems in order to probe the interaction between the chromophores. The results of the transient decays as well as fluorescence anisotropy decay times gives stronger proof to the suggestion of delocalized states in the cyclic macrocycles. These results provide information regarding the optical properties of these novel systems useful for potential applications in photonics.     

Disorder in condensed matter systems: proton spin lattice relaxation study of the mixed systems of betaine phosphate and glycine phosphite, BPxGPI(1-x)

Proton NMR relaxation measurements have been carried out in the mixed system of antiferroelectric (AFE) betaine phosphate (BP) and ferroelectric (FE) glycine phosphite (GPI), BPxGPI(1-x), at 11.4 and 23.3 MHz from 300 to 100 K for x=0.3, 0.4, 0.5, 0.6, 0.7 and 0.8. The temperature dependence of spin lattice relaxation (SLR) time follows the BPP model in the parent compounds, while the Larmor frequency dependence of T1 in the mixed system is rather unusual. The T1 curve exhibits different slopes for the low-temperature wings at the two frequencies, which is a clear experimental evidence of the presence of different methyl groups with different activation energies (Ea), indicating disorder. For x=0.3 and 0.4, biexponential recovery of magnetization has been observed below 190 K, showing that the degree of disorder varies with the concentration. The temperature dependence of relaxation time data has been interpreted in terms of NH3, trimethyl ammonium and methyl group reorientations.     

DNA binding and oxidative cleavage activity of ternary (l-proline)copper(II) complexes of heterocyclic bases

Ternary copper(II) complexes [Cu(l-pro)(B)(H₂O)](NO₃) (1, 2) where l-pro = l-proline, B is a N,N-donor heterocyclic base, viz. 2,2′-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2), are synthesized, characterized, and their DNA binding and cleavage activity studied. The bpy complex (1) is structurally characterized by single-crystal X-ray crystallography. The complexes show the presence of a distorted square-pyramidal (4 + 1) CuN₃O₂ coordination geometry. Complex [Cu(l-pro)(bpy)(H₂O)](NO₃) (1) crystallizes in the triclinic space group P1 with unit cell parameters: a = 7.082(3) Å, b = 10.483(5) Å, c = 11.581(5) Å, α = 89.700(7)°, β = 83.488(8)°, γ = 84.109(8)° and V = 849.7(7) Å³. The one-electron paramagnetic complexes display a d–d band near 600 nm in water and show a cyclic voltammetric response due to Cu(II)/Cu(I) couple near 0.1 V (versus SCE) in Tris–HCl buffer–0.1 M KCl. Binding interactions of the complexes with calf thymus (CT) DNA have been investigated by emission, absorption, viscosity and DNA thermal denaturation studies. The phen complex displays significant binding propensity to the CT DNA giving an order: 2 (phen)  1 (bpy). The bpy complex does not show any apparent binding to the DNA and hence poor cleavage efficiency. Complex 2 shows efficient oxidative cleavage of SC-DNA in the presence of 3-mercaptopropionic acid (MPA) involving hydroxyl radical species as evidenced from the control data showing inhibition of DNA cleavage in the presence of DMSO and catalase.     

Quantification of pramipexole in human plasma by liquid chromatography tandem mass spectrometry using tamsulosin as internal standard

A high-performance liquid chromatography/electrospray ionization tandem mass spectrometry method was developed and validated for the quantification of pramipexole in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M + H](+) ions, m/z 212/152 for pramipexole and m/z 409/228 for the IS. The method exhibited a linear dynamic range of 200-8000 pg/mL for pramipexole in human plasma. The lower limit of quantification was 200 pg/mL with a relative standard deviation of less than 8%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 3.5 min for each sample made it possible to analyze more than 200 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.     

The sulfinyl moiety as an internal nucleophile. 2. Stereoselective synthesis of (-)-galantinic acid via 1,3-asymmetric induction

A stereoselective synthesis of (-)-galantinic acid is disclosed. The key steps include hydrolytic kinetic resolution of a racemic epoxide and regio- and stereoselective heterofunctionalization of an olefin, using a pendant sulfinyl group as the nucleophile. The participation of the sulfinyl group was unambiguously proven by conducting the reaction in the presence of H(2)(18)O.     

Studies on the solvent extraction behaviour of Pu(IV) from sulfuric acid medium into di-2-ethylhexyl phosphoric acid (HDEHP)

Extraction of plutonium(IV) from aqueous sulfuric and sulfuric-nitric acid into di-2-ethylhexyl phosphoric acid (HY) in the diluents n-dodecane, toluene or chloroform has been investigated. The composition of the Pu(IV) species extracted from H₂SO₄ was found to be PuH₂Y₆, which changed to Pu(NO₃)H₂Y₅ and Pu(NO₃)₂H₂Y₄ with increasing concentration of nitrate ion in the aqueous medium. These three species can be represented as PuY₂(HY₂)₂, Pu(NO₃)Y(HY₂)₂ and Pu(NO₃)₂(HY₂)₂, respectively, where Y represents the anion of monomeric HY, and HY₂ the anion of dimeric H₂Y₂. Synergism in the extraction of Pu(IV) by the addition of thenoyltrifluoroacetone (HTTA) to HY was also investigated and attributed to extraction of the additional species, Pu(TTA)Y(HY₂)₂ and Pu(TTA)₂(HY₂)₂. The addition of the neutral extractant tri-n-octylphosphine oxide (TOPO) to HY did not result in synergism in the extraction of Pu(IV) from aqueous sulfuric acid. With aqueous nitric acid under similar conditions, however, synergism was observed. The possible equilibria in these systems were identified and the corresponding equilibrium constants were determined.     

Liquid chromatography/electrospray ionization mass spectrometry method for the quantification of valproic acid in human plasma

A simple, sensitive and rapid liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) method was developed and validated for the quantification of valproic acid, an antiepileptic drug, in human plasma using benzoic acid as internal standard (IS). Following solid-phase extraction, the analytes were separated using an isocratic mobile phase on a reversed-phase C18 column and analyzed by MS in the single ion monitoring mode using the respective [M-H]- ions, m/z 143 for valproic acid and m/z 121 for the IS. The assay exhibited a linear dynamic range of 0.5-60 microg/mL for valproic acid in human plasma. The lower limit of quantification was 500 ng/mL with a relative standard deviation of less than 10%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The average absolute recoveries of valproic acid and the IS from spiked plasma samples were 96.1+/-4.2 and 95.6+/-2.7%, respectively. A run time of 4.5 min for each sample made it possible to analyze more than 250 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability and bioequivalence studies.     

Kinetics of the dissociation of tris(1,10-phenanthroline) iron(III) complex ion in aqueous acid solutions. A mechanistic model for product specificity

Summary The natural decay of Fe(phen) _f3 ^p3+ , where no Ce^IV is employed for scavenging the side reaction product, Fe(phen) _f3 ^p2+ , is now treated as a complex reaction involving two parallel processes, and the experimental kinetics are consistent with the rate laws derived from a mechanism that simultaneously explains the composition of the products as a function of acidity. In terms of the proposed mechanism the dissociation rate of the complex ion in acid solutions containing Ce^IV as scavenging agent is to be regarded as a Ce^IV retarded aquation rate, and OH^– is to be assigned a catalytic role in the kinetics of basic reduction.     

Concentration with Selective Acid Removal from Americium Solutions Using Ion Exchange Membranes

Donnan dialysis and diffusion dialysis techniques are investigated for deacidification and possible concentration of actinide bearing acidic streams. Cation and anion exchange membranes are used in a two compartment dialysis cell to selectively remove acid from americium solutions. Acid concentrations, as high as 8.0M HNO₃ are used and the stability of membranes are ascertained. Possibility of simultaneous deacidification and concentration of acidic americium solutions are indicated by combining simple osmosis with diffusion dialysis. All the experiments are carried out under non stirring conditions at room temperature.