The importance of keto-enol tautomerism in alloxan. A semi-empirical quantum mechanical study

1148-115

Triazole-based C3-symmetric multivalent dendritic architecture as Cu(II) ion sensor

C3-symmetric triazole-based multivalent dendritic architecture having uniform aromatic core and branches has been employed to study its metal binding ability towards Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) ions. The dendritic architecture is found to exhibit a high affinity for Cu(II) ions and formed a solid complex with a blue shift in the dd-band of Cu(II) chloride. X-band EPR spectra at low temperature has supported a distorted tetrahedral geometry for the complex. The complex has displayed quasi-reversible redox waves in cyclic voltammetry (CV). DFT calculations have shown that Cu(II) has a high affinity for the dendritic structure, leading to high complexation energies of the order of -25 eV, showing that the complexation reactions are highly exothermic. The binding constant (K) for the Cu(II) complex has been determined using a fluorescence titration method

Atomic and molecular spectroscopy: basic concepts and applications

Spectroscopy is the study of electromagnetic radiation and its interaction with solid, liquid, gas and plasma. It is one of the widely used analytical techniques to study the structure of atoms and molecules. The technique is also employed to obtain information about atoms and molecules as a result of their distinctive spectra. The fast-spreading field of spectroscopic applications has made a noteworthy influence on many disciplines, including energy research, chemical processing, environmental protection and medicine. This book aims to introduce students to the topic of spectroscopy. The author has avoided the mathematical aspects of the subject as far as possible; they appear in the text only when inevitable. Including topics such as time-dependent perturbation theory, laser action and applications of Group Theory in interpretation of spectra, the book offers a detailed coverage of the basic concepts and applications of spectroscopy

Methyl nitrene: Thermochemistry and kinetics of its rearrangement to methyleneimine

308-312The thermal unimolecular isomerisation of methylnitrene to methyleneimine has been studied, and the macroscopic thermodynamic and kinetic properties have been calculated using the vibrational frequencies and rotational constants evaluated theoretically. The high pressure rate constants have been calculated and the fall-off behaviour has been studied using the calculated reactant and transition state properties. Kinetic isotope effects on the reaction have also been studied. The effects of fluorine substitution on the thermochemical and kinetic parameters have also been investigated

Structures of some Hoechst analogues in gas phase and in aqueous solution

1929-1936Four Hoechst analogues have been examined in this work to determine their conformational preferences in three different environments, viz. gas phase, within the DNA minor groove and aqueous phase. Rotations about all the three single bonds, namely those connecting the phenol ring to a benzimidazole ring, the two benzimidazole rings, and a benzimidazole ring to the N-methylpiperazine ring have been considered. It is found that the optimum conformation necessary for binding to the DNA minor groove is easily attained, especially in aqueous solution

Resveratrol: A Polyphenol with Multiple Health Benefits

In today's stressful world, there is an urgent need for simple drugs to combat lifestyle diseases like heart diseases and diabetes, which are assuming epidemic proportions. Resveratrol is one such molecule. It is the molecule behind a phenomenon known as the “French paradox”, i.e. the observation of low incidence of heart disease in France in spite of a diet rich in fats. It is a major component of red wine, also part of the French diet. Resveratrol is a naturally occurring polyphenolic phytoalexin, derived from the skin of plants, which has gained interest exponentially in recent years. This molecule is found to have a number of health benefits, including prevention of cardiovascular and neurodegenerative diseases. It is known to have anti-inflammatory, antiviral, anti-platelet aggregation and many other health beneficial properties. It has found tremendous clinical application. Among its wide range of biological activities, the most striking activity is of cancer and tumor initiation prevention. This molecule has been shown to have a positive effect on metabolism and improvement in overall health of an individual and can probably be used as an anti ageing drug alone or in combination with some other medication. These remarkable properties have elicited a huge interest of researchers in this molecule. It has been reported to interfere with some major cellular signaling pathways which are involved in cell survival or cell death. Careful insights into these cellular pathways and their interaction with resveratrol could pave the way for future drug designing for treatment of diseases. Here we have tried to review the maximum possible biological properties of resveratrol cited so far in the literature

Semiempirical study of tautomerism in alloxan

103-111A comparative semiempirical study of tautomerism in alloxan is performed with a view to understand the areas of applicability and limitations of the three methods, MNDO, AM1 and PM3. The results are also compared with an ab initio study. It is found that the MNDO method overestimates the stability of lactim forms, while AM1 method seems to underestimate their stabilities. All methods indicate that the tetraketo form is the most stable, followed by the monohydroxy forms. While the PM3 method seems to give the best results regarding relative stabilities of tautomers, it fails in reproducing experimental geometries and charge distributions and in explaining the chemical and biological reactivity of alloxan. The calculated MNDO and AM1 charge densities agree with the results of an ab initio study and with experimental estimates, and are thus able to explain the absence of hydrogen bonding in the crystal structure of alloxan. Nucleophilic attack by water at 5-position leads to a significant increase in the stabilities of the tetraketo and 2-hydroxy forms. Thus, due to the absence of hydrogen bonding interactions in the crystal structure of alloxan, the MNDO geometries are in closest agreement with experiment, and the charge densities are also consistent with experimentally estimated ones

<span style="font-size:12.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-ansi-language: EN-IN;mso-fareast-language:EN-IN;mso-bidi-language:AR-SA" lang="EN-IN">C₃H₄: Interconversion of isomers</span>

1262-1269<span style="font-size:12.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-ansi-language:="" en-in;mso-fareast-language:en-in;mso-bidi-language:ar-sa"="" lang="EN-IN">The reaction paths for the thermal interconversion of the various C3H4 isomers have been studied by the MNDO method and the activation barriers to the various isomerizations have been estimated. The transition state structures have been analyzed in terms of the orbital compositions of the frontier molecular orbitals and the overlap populations of the various bonds involved in the transition states. These have been interpreted to understand the mechanisms of the various interconversions. Vinylmethylene is found to play a central role in the isomerizations as its formation from the stable isomers, and subsequent rearrangement to the other isomers, is the most facile process among the various other competing reactions. The anti nonplanar geometry of vinylmethylene is found the intermediate in the interconversions.</span