Crystal growth of some urinary stone constituents: II. In‐vitro crystallization of hippuric acid

Hippuric acid [C₆H₅CONHCH₂COOH], one of the organic chemical constituents of urinary stone is crystallized in silica gel under suitable pH conditions by double diffusion method. The grown crystals were characterized by density measurement, Fourier transform infrared spectroscopy, X‐ray powder diffraction and thermogravimetric analysis.     

Studies of isomer stability using the maximum hardness principle (MHP)

In the present study, a number of positional and geometrical isomers have been considered to study the stability of isomers using the maximum hardness principle (MHP). All the considered isomeric molecules were optimized and the chemical hardness η and chemical potential μ were calculated at the HF/6‐31G level of theory. The MHP was not able to predict the stability of the most of the positional isomeric molecules, because of the variation in the chemical potential μ and external potential v(r), which arises due to the formation of a bond with different atoms. But, for the most of geometrical isomers, the MHP was able to predict the most stable conformer of the molecule. So, the present investigation suggests that the MHP is not applicable for the prediction of isomer stability for all the isomeric molecules. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 76: 648–655, 2000     

Total Synthesis of Vancomycin Aglycon—Part 3: Final Stages

A triazene-based synthetic strategy for the construction of the complex biaryl ethers and a Suzuki coupling reaction were the key steps in the synthesis of precursor 1 of the aglycon of vancomycin, which already contains the complete skeleton of the target compound. The cleavage of the triazene unit from the D ring and the removal of the other protecting groups led to the aglycon of vancomycin. These strategies should be particularly valuable for the synthesis of other naturally occurring glycopeptide antibiotics and offer opportunities for the synthesis of combinatorial libraries of compounds of the vancomycin family for chemical biology studies.     

High-rate electrochemical performance and structure elucidation of hydrothermally synthesized nickel zincate nanorods

Journal of Solid State Electrochemistry - For the first time, nanorods of nickel zincate (NiZnO2) have been synthesized by the hydrothermal method and used in supercapacitor electrode fabrication....     

Electron–phonon coupling and vibrational modes contributing to linear electro‐optic effect of the efficient NLO chromophore 4‐(N,N‐dimethylamino)‐N‐methyl‐4′‐toluene sulfonate (DAST) from their vibrational spectra

The optimized geometry and structural features of the most prospective electro‐optic crystal 4‐(N,N‐dimethylamino)‐N‐methyl‐4′‐toluene sulfonate (DAST), and the vibrational spectral investigations have been comprehensively described with the near infrared Fourier transform (NIR FT) Raman and Fourier transform infrared (FT‐IR) spectra supported by the density functional theoretical (DFT) computations to elucidate the contribution of vibrational modes to the linear electro‐optic (LEO) effect. Mulliken population analysis and natural bond orbital (NBO) analysis have also been carried out to analyze the effects of intramolecular charge transfer (ICT), intramolecular hydrogen bonding and hyperconjugative interactions on the geometries. The influence of CT interaction between the phenyl ring and the dimethylamino group of the nonlinear optical (NLO) chromophore on the endocyclic and exocyclic angles, and the electronic effects such as hyperconjugation and back‐donation on the methyl hydrogen atoms have been examined. The concurrent intense activation of Raman and IR activities of the effective conjugation vibrational coordinate, which significantly contributes to the LEO effect resulting from the strong electron–phonon (e/ph) coupling, has been analyzed in detail. The effects of frontier orbitals, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), transition of electron density (ED) transfer and the influence of planarity in the stilbazolium ring on the first hyperpolarizability are also discussed. Copyright © 2008 John Wiley & Sons, Ltd.