Synthesis, growth and characterization of nonlinear optical crystal: l-tyrosine hydrobromide

l-tyrosine hydrobromide (l-THB) a semi organic nonlinear optical material with molecular formula C₉H₁₂NO₃Br has been synthesized at ambient temperature. Spectral, thermal and optical techniques have been employed to characterize the new material. The solubility of l-THB at varying temperatures was determined in different concentrations of hydrobromic acid. Bulk single crystals of size 15×7×4 mm³ of l-THB were grown by slow evaporation method at constant temperature. Powder X-ray diffraction pattern of the grown l-THB has been indexed. Functional groups present in the sample were identified by FTIR spectral analysis. Chemical composition of the synthesized material was confirmed by carrying out CHN analysis. Thermal stability of l-THB was determined from TGA/DTA and DSC response curves. Mechanical hardness of the grown crystal l-THB was determined and Vickers hardness number was calculated. The Kurtz powder second harmonic generation test shows that the compound is a potential candidate for optical second harmonic generation. The optical transparency range and the lower cut-off of UV transmission were identified from the recorded UV-vis spectrum of l-THB. The optical energy gap of l-THB is 3 eV.     

Solution growth of new ferroelectric glycine phosphite unidirectional single crystals at room temperature

Glycine phosphite [NH₃CH₂COOH₃PO₃], abbreviated as GPI is the second hydrogen bonded ferroelectric crystal combination of phosphorous acid and amino acid following βnine phosphite crystals abbreviated as BPI. Sankaranarayanan and Ramasamy‐Technique was adopted to prepare the ferroelectric glycine phosphite unidirectional single crystal. The growth orientation was imposed by the pre‐grown 〈010〉 seed. As water was the solvent, transparent, colourless crystal with cylindrical shaped ingot of sized 20mm‐diameter was grown. Powder X‐ray diffraction, HRXRD, FTIR, dielectric and mechanical studies were carried out. The results are discussed in detail. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Studies on distribution of radionuclides and behavior of clay minerals in the soils of river environs

Journal of Radioanalytical and Nuclear Chemistry - In the present investigation, the activity concentrations of radionuclides in the soils of Cauvery river environs were measured using HPGe gamma...     

A facile synthesis of pyrano[2,3-d:6,5-d′]dipyrimidines via microwave-assisted multicomponent reactions catalyzed by β-cyclodextrin

A facile three-component reaction of aromatic aldehyde, 2,2-dimethyl-1,3-dioxane-4,6-dione, and 6-amino-1,3-dimethyluracil was developed for the first time using β-cyclodextrin (β-CD) as a macrocyclic host for aldehyde and an efficient catalyst that leads to a batch of novel pyrano[2,3-d:6,5-d′]dipyrimidines ( 4a-k ). The synthesis was accomplished with the aid of microwave irradiations in solvent-free conditions. The product obtained was in contrast to the previous report in which a similar reaction resulted in a mixture of benzylidenepyrimidine and bisaminopyrimidine analogs in the presence of triethylbenzylammonium chloride in an aqueous medium. The formation of the pyrano[2,3-d:6,5-d′]dipyrimidines may be in virtue of the property of β-CD to construct new C C and C X (where X = heteroatom) bonds. Reusability of the catalyst up to three runs without any noteworthy change in catalytic activity is one of the main features of the reaction. Other noteworthy features are good to excellent yields, eco-friendly procedure, non-column chromatographic purification, and mild conditions.     

An Improved Process for the Enantioselective Synthesis of HCV NS5A Inhibitor Elbasvir (MK-8742) Chiral Amine Intermediate

Russian Journal of General Chemistry - Large-scale enantioselective synthesis of the chiral amine unit of HCV NS5A inhibitor Elbasvir has been accomplished in six steps, with 55% overall yield. The...     

Broadband supercontinuum generation in a single potassium di-hydrogen phosphate (KDP) crystal achieved in tandem with sum frequency generation

We present here an enhanced broadband supercontinuum generation in a potassium di-hydrogen phosphate (KDP) crystal. The enhancement in the bandwidth of the white light is obtained towards the shorter wavelength regime (<400 nm) by employing supercontinuum generation and sum frequency generation in tandem. The tunability in the blue region of the spectrum with angle is demonstrated. The bandwidth of supercontinuum achieved spans from 350 nm to 1300 nm. Further, we show the excellent polarization maintenance of continuum generated in KDP in comparison to that generated in water and BK-7 glass. PACS 42.65.Ky; 42.65.Jx; 42.65.Re; 42.25.Ja     

Acetoxyborohydride: A Simple Selective Hydroborating Agent

Acetoxyborohydride (CH₃COO$\text{B}$H₃) hydroborates olefins in the presence of some reducible functional groups.     

Measurement of optical constants of thin polymer films using spectrally resolved white light interferometry

Using the spectrally resolved white light interferometry we present our experimental results on the measurement of the optical constants of thin polymer films coated on a transparent substrate. As an extension to our previous work (J. Opt. Soc. Am. B12, 1559 (1995)) on thick glass plates, we have shown here that this technique can be effectively applied to very thin polymer films also. We have improved the accuracy of our results by using the Sellmeier dispersion formula for fitting the data. From the width and position of the zero-order fringe and the frequency of modulations in the white light spectrum, the refractive indexn(λ) and thicknesst of the thin polymer films are calculated. To study the accuracies involved in the technique, PVA, PMMA and PS films of varied thicknesses are coated on glass plates and the measured values are compared with ellipsometer studies.     

In vivo proton magnetic resonance spectroscopy studies of human brain

In vivo localized proton magnetic resonance spectroscopy (MRS) studies of brain were performed on eighteen normal subjects using the stimulated echo (STE) sequence. The absolute concentrations and proton relaxation times of N-acetyl aspartate (NAA), total creatine (Cr) and choline (Cho) were estimated. The MRS data was quantitatively analyzed for repeatability and intersubject variability. Quantitative analysis indicates excellent spectral repeatability. Significant intersubject variations in [NAA] and [Cr] have been observed while the intersubject variability in [Cho] has been found to be fairly small. Significant intensity distortions have been observed for mixing times longer than 50 msec.