An experimental NMR and computational study of 4-quinolones and related compounds

Abstract  

We report the synthesis and structural study of eight compounds, either quinolin-4(1H)-ones or quinolines. Tautomerism as well as (E) → (Z) and rotational isomerism were studied both experimentally (¹H and ¹³C NMR) and theoretically [B3LYP/6-311++G(d,p)].     

Synthesis of new metalloporphyrin triads: efficient and versatile tripod optical sensor for the detection of amines

Zinc and manganese complexes of porphyrin triads have been synthesized and are shown to be efficient as highly sensitive and selective tripod optical sensors for amines at the picomolar level.     

New model describing adsorption from liquid binary mixtures of nonelectrolytes with limited and unlimited miscibility of components

Using the thermodynamic idea of complementary systems, and based on fundamental concepts of the theory of volume filling of micropores, we derived a new universal model describing adsorption from solutions with limited and unlimited miscibility of components. The model takes into account the differences in collision diameters of adsorbed molecules as well as the competitive nature of adsorption from solutions. The applicability of this new approach is tested against experimental data.     

Synthesis and reactivity of 6‐methyl‐4H‐furo[3,2c]pyran‐3,4‐dione

An efficient synthesis of 3‐bromoacetyl‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one by bromination of dehydroacetic acid in glacial acetic acid is described. Novel 4‐hydroxy‐6‐methyl‐3‐(2‐substituted‐thiazol‐4‐yl)‐2H‐pyran‐2‐ones have been prepared from the reaction of 3‐bromoacetyl‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one with thioamides, thiourea, and diphenylthiocarbazone. The condensation reaction of 6‐methyl‐4H‐furo[3,2c]pyran‐3,4‐dione, obtained from the reaction of 3‐bromoacetyl‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one with aliphatic amines, with benzaldehydes and acetophenones led to novel 2‐arylidene‐6‐methyl‐2H‐furo[3,2‐c]pyran‐3,4‐diones and 6‐(2‐arylprop‐1‐enyl)‐2H‐furo[3,2‐c]pyran‐3,4‐diones. The structure of all compounds was established by elemental analysis, IR, NMR, and mass spectra. J. Heterocyclic Chem., 2011.     

cis-Glyco-fused benzopyran compounds as new amyloid-β peptide ligands

A small library of glyco-fused benzopyran compounds has been synthesised. Their interaction features with Aβ peptides have been characterised by using STD-NMR and trNOESY experiments. The conformational analysis of the compounds has also been carried out through molecular mechanics (MM) and molecular dynamics (MD) simulations.     

Modulating the self-assembly of rigid "clicked" dendrimers at the solid-liquid interface by tuning non-covalent interactions between side groups

First generation poly(triazole-phenylene) dendrimers equipped with peripheral alkyl or carboxylic acid groups to engage in van der Waals and hydrogen-bonding interactions, respectively, assemble into distinct two-dimensional nano-structures at the solid-liquid interface as revealed by high resolution STM investigations.     

High spin metastable state relaxation of spin-crossover solids driven by white noise

The mean first passage time (MFPT) as dwell time in high spin metastable state of spin-crossover solids is investigated both analytically and numerically. Calculations showed that the MFPT decreases with the increases of a distance from metastable state. The probability density function has also been examined.     

Pre-inflationary homogenization of scalar field cosmologies

We consider the evolution of covariant and gauge invariant linear density perturbations of scalar field cosmologies using a dynamical systems? approach. We find conditions for which the perturbations decay in time, so that the spacetime approaches a homogeneous solution which inflates, for quadratic and exponential potentials. This pre-inflationary homogenization is found to be stable in the potentials? parameter spaces. Furthermore, in each case, we determine the minimum size of the resultant homogeneous patch and show that, for quadratic potentials, the resulting inflationary solutions include those with the necessary number of e-folds.     

The influence of the carbon surface chemical composition on Dubinin-Astakhov equation parameters calculated from SF6 adsorption data-grand canonical Monte Carlo simulation

Using grand canonical Monte Carlo simulation we show, for the first time, the influence of the carbon porosity and surface oxidation on the parameters of the Dubinin-Astakhov (DA) adsorption isotherm equation. We conclude that upon carbon surface oxidation, the adsorption decreases for all carbons studied. Moreover, the parameters of the DA model depend on the number of surface oxygen groups. That is why in the case of carbons containing surface polar groups, SF(6) adsorption isotherm data cannot be used for characterization of the porosity.     

Intense red upconversion fluorescence emission in NIR-excited erbium-ytterbium doped laponite-derived phosphor

In this report the optical properties and energy-transfer frequency upconversion luminescence of Er³⁺/Yb³⁺-codoped laponite-derived powders under 975 nm infrared excitation is investigated. The 75%(laponite):25%(PbF₂) samples doped with erbium and ytterbium ions, generated high intensity red emission around 660 nm and lower intensity green emission around 525, and 545 nm. The observed emission signals were examined as a function of the excitation power and annealing temperature. The results indicate that energy-transfer, and excited-state absorption are the major upconversion excitation mechanism for the erbium excited-state red emitting level. The precursor glass samples were also heat treated at annealing temperatures of 300 °C, 400 °C, 500 °C, and 600 °C, for a 2 h period. The dependence of the visible upconversion luminescence emission upon the annealing temperature indicated the existence of an optimum temperature which leads to the generation of the most intense and spectrally pure red emission signal.