Guanidinium nitrate: a novel reagent for aryl nitrations

Nitration of various aromatic compounds utilising guanidinium nitrate in 85% sulfuric acid as a nitrating agent has been studied.     

Nonlinear electron transport properties of InAlAs/InGaAs based Y-branch junctions for microwave rectification at room temperature

A detailed analysis of nonlinear effects-electron switching and rectification, in InAlAs/InGaAs based Y-branch junction (YBJ) devices is presented to investigate the potential of YBJ for high frequency applications at 300 K. Results based on semi-classical simulations yield good qualitative agreement with measurements and previously reported theoretical and experimental results. The nonlinear parabolic behaviour of our device is attributed to device geometry and space charge effects. RF analysis shows that the YBJ has tremendous intrinsic potential to function as a frequency doubler and microwave rectifier when operated in the parabolic regime. The present analysis serves as a tool to optimize the bias conditions for RF measurements and to estimate the effect of interconnects and parasitic elements on the RF performance of real devices.     

Degradation process in organic thin film devices fabricated using P3HT

The stability of regioregular poly(3-hexylthiophene 2,5-diyl) (P3HT) thin films sandwiched between indium tin oxide (ITO) and aluminium (Al) electrodes have been investigated under normal environmental conditions (25°C and RH∼45–50%). Electrical and optical properties of ITO/P3HT/Al devices have been studied over a period of 30 days. Mobility μ of the order of 10⁻⁴ cm²/V-s has been obtained from the V ² law in the as-deposited P3HT films. Scanning electron microscopy (SEM) investigations show blistering of Al contacts in devices with a poly(3,4-ethylenedioxythiophene) (PEDOT) interlayer on application of voltage whereas no blistering is seen in devices without PEDOT. The results have been explained in terms of trap generation and propagation and the moisture-absorbing nature of PEDOT.      

Thin layer chromatographic studies of anils II. Separation,identification and determination

Thin layer chromatographic behaviour of ten anils was studied on silica gel adsorbent mixed with starch binder with ten solvent systems. Simultaneous separation, identification and determination of ternary mixtures of isomers was stressed. TheR _F increasing order was found to be dependent on the solvent and independent of the degree of saturation of the chamber. The correlations ofR _F with _max and (C=O) of isomers were established and used in their identification. Six anils were separated in methanol—benzene (11).     

Five-coordinate Cobalt(II), Nickel(II) and Zinc(II) Complexes Derived from 2-pyridine-2-yl-3-(pyridine-2-carboxylideneamino)-1,2-dihydroquinazolin-4(3H)-one. The Crystal Structure of the Cobalt(II) Complex

The synthesis of cobalt(II), nickel(II) and zinc(II) complexes of 2-pyridine-2-yl-3(pyridine-2-carboxylideneamino)-1,2-dihydroquinazolin-4(3H)-one is described. The ligand and metal complexes were characterized by elemental analysis, conductivity measurements, spectral (u.v.–vis., i.r., 1D n.m.r., 2D hetcor and mass) and thermal studies. The cobalt(II) complex crystallizes as pink crystals in the monoclinic crystal system, space group P21/n with a = 10.066(6) Å, b = 15.929(9) Å, c = 12.624(7) Å, α = 90.00(9)°, β = 110.850 (8)°, γ = 90.00, V = 1891.5 (18) ų and Z = 4. The geometry around the cobalt atom is distorted trigonal bipyramidal with τ = 0.83 [structural parameter, τ = (β − α)/60; where α and β are the two basal angles in a five coordinate complex].     

Structure, reactivity and aromaticity of acenes and their BN analogues: a density functional and electrostatic investigation

Density functional calculations have been carried out on a series of linearly annelated acenes and their BN analogues. Even though borazine shows aromatic and reactivity behavior parallel with that of benzene, its condensed derivatives show patterns different from those of their hydrocarbon analogues. Nucleus independent chemical shift (NICS) values in acenes suggest that the aromaticity of the inner rings is more than that of benzene, whereas in BN-acenes there is no substantial change in the aromaticity of the individual rings. Molecular electrostatic potential (MESP) is employed to obtain further insights into the bonding and reactivity trends for these systems. The MESP topography patterns of acenes and BN-acenes are substantially different, with BN-acenes showing more localized pi electron features compared to those of acenes. The MESP values at the critical points (CPs) indicate overall lowering of aromaticity in these annelated systems. However, this change is gradual among the BN-acenes.     

Kinetics and mechanism of the ruthenium(III)-catalyzed oxidation of hydroxy-acids byN-bromosuccinimide

Summary The kinetics of the Ru^III-catalyzed oxidation of the hydroxy acids; lactic, tartaric, malic and citric acids byN-bromosuccinimide in HClO₄ and in the presence of Hg(OAc)₂ have been studied. The reactions exhibit a first order rate dependence with respect to the oxidant and zeroth order rate dependence with respect to substrate. The rate is retarded by [H⁺], accelerated at law Ru^III concentrations but independent of [Ru^III] at higher Ru^III concentrations. A mechanism consistent with the observed kinetic data is proposed.     

Nucleophilic substitution in certain bicyclic sesquiterpene alcohols under chemical lonization conditions

Substitution of amino for hydroxyl groups in certain sesquiterpene alcohols has been studied by chemical ionization mass spectrometry using ammonia and ammouia-d₃ as the reagent gases, and by mass-analysed ion kinetic energy spectrometry and collision-induced decomposition mass-analysed ion kinetic energy measurements. Depending upon the source conditions and the nature of the substrates, both S_Ni and S_N1 mechanisms have been found to operate. No evidence is obtained for an S_N2 mechanism in these compounds. In centdarol and isocentdarol, addition of NH₃ to the double bond, followed by elimination of H₂O, also contributes to the substitution process. Attack of [NH₄]⁺ on the epoxide function, followed by loss of H₂O, appears to lead to the substitution ions in epoxycentdarol, epoxyisocentdarol and epoxyhimachalol.     

Translational hydrodynamics for binary mixtures: Memory from internal molecular relaxation

We consider a binary fluid mixture made up of a monatomic species and a two level molecular species and investigate the decay of correlations in the hydrodynamic variables. By restricting our considerations to the translationally hydrodynamic situations, we deduce a set of generalised hydrodynamic equations in which the frequency, ω, and wavenumber, k, dependent memory arises solely from the internal molecular relaxation. From these generalised hydrodynamic equations, we identify various (k, ω) dependent transport coefficients and the relaxation time which depends on k. We also compute the spectrum of (polarised) light scattered from such a binary mixture. We illustrate the dependence on k, ω and concentration in the problem by a numerical calculation of the generalised transport coefficients, the Rayleigh-Brillouin spectrum and the dispersion of various modes in this spectrum for the case of thermal relaxation in a parahydrogen-helium mixture.     

Complexes of a new series of α-diimine macrocycles,I: Template synthesis of cadmium(II) complexes of tetraazamacrocycles derived from 2,3-butanedione or benzil

Summary Cadmium(II) complexes of the type [CdL] (NO₃)₂ (whereL = tetraazamacrocycle with a 12 to 32-membered ring) have been synthesized by the reactions of 2,3-butanedione or benzil with different aliphatic diamines viz. ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,6-diaminohexane, 1,8-diaminooctane and 1,12-diaminododecane in the presence of Cd(II) as template. These complexes have been characterized by elemental analyses, conductivity measurements and IR and NMR spectral studies.

---

Komplexe einer neuen Serie von -Diimin-Macrocyclen, 1. Mitt.: Synthese von Cadmium(II)-Komplexen von Tetraazamacrocyclen aus 2,3-Butandion oder Benzil

Zusammenfassung Es wurden Cadmium(II)-Komplexe des Typs [CdL] (NO₃)₂ (wobeiL einen 12-bis 32-gliedrigen Tetraazamacrocyclus darstellt) mittels der Reaktion von 2,3-Butandion oder Benzil mit verschiedenen aliphatischen Diaminen (Ethylendiamin, 1,3-Diaminopropan, 1,4-Diaminobutan, 1,6-Diaminohexan, 1,8-Diaminooctan und 1,12-Diaminododecan) hergestellt. Die Komplexe wurden mittels Elementaranalyse, Leitfähigkeitsmessungen und Infrarot- bzw. Kernresonanzspektroskopie charakterisiert.