1H NMR Elucidation of Observed Stable Sugar-NaCl-water Complexes in Aqueous Solution

The solvation of sugars in aqueous media matters in the understanding of biological systems and carbohydrate transformations. Generally, 2 – 4 water units were proposed to interact with each hydroxyl group in monosaccharides via different types of hydrogen bondings at room temperature in previous studies. Presence of NaCl was known to perturb hydrogen bondings of sugar hydrates. However, direct evidence to elucidate mechanism at atom level is very rare even though “NaCl Effect” was well known in biomass chemical transformations. Here we report 1H NMR elucidation evidences of mono/disaccharides hydrates in different concentration of NaCl aqueous solutions. We here conclude two new findings: 1) under ideal usage of NaCl, different mono/disaccharides hydrates are likely to be converted into a stable sugar-NaCl-water form; 2) pKa value of different hydroxyls in mono/disaccharides has intangible influence on hydrate form change induced by NaCl. An ideal NaCl usage based on maximum of 1H NMR shift was proposed.

Efficient and Low-Cost Removal of Methylene Blue using Activated Natural Kaolinite Material

Clays are low-price and very useful material for water treatment purpose. In this work, we reported the application of activated natural kaolinite material which obtained from Wediombo beach, Yogyakarta for methylene blue adsorption. The natural kaolinite material was activated under an acidic condition to obtain the activated kaolinite material. The activated kaolinite material was characterized using Fourier transform infrared, X-ray diffraction, scanning electron microscope, and surface analysis. From the adsorption experiment, the activated kaolinite material gave moderate adsorption percentages for methylene blue. The adsorption kinetics followed the Ho and McKay kinetic model while the adsorption isotherm followed Langmuir model. The qmax value for methylene blue adsorption using activated natural kaolinite material was at a moderate level (3.40 mg g-1). The plausible adsorption mechanism of methylene blue on the surface of activated kaolinite material happened through hydrogen bondings and/or electrostatic interactions. These findings are important for a wastewater treatment using a low-cost adsorbent material.

A Molecular Interpretation of the Dynamics of Diffusive Mass Transport of Water Within a Glassy Polyetherimide

The diffusion process of water molecules within a polyetherimide (PEI) glassy matrix has been analyzed by combining the experimental analysis of water sorption kinetics performed by FTIR spectroscopy with theoretical information gathered from Molecular Dynamics simulations and with the expression of water chemical potential provided by a non-equilibrium lattice fluid model able to describe the thermodynamics of glassy polymers. This approach allowed to construct a convincing description of the diffusion mechanism of water in PEI providing molecular details of the process related to the effects of the cross- and self-hydrogen bondings established in the system on the dynamics of water mass transport.

[38]Octaphyrin bis-Sn(IV) complexes with unique coordination geometries

Metal complexation of octaphyrin(1.1.1.1.1.1.1.1) triggers unique ring-fixation aptitudes or unexpected rearrangement (cleavage) reactions. In this paper, a unique complexation behavior of [38]octaphyrin upon tin(IV) metalation is showcased. Two new [38]octaphyrin bis-Sn(IV) complexes 2Sn and 3Sn were isolated and characterized as weakly aromatic molecules. While 2Sn with the [Formula: see text] molecular symmetry displayed a similar characteristic to octaphyrin bis-Si(IV) and bis-Ge(IV) complexes reported previously, 3Sn showed a different coordination mode that is fixed by intramolecular hydrogen bondings between pyrrolic NH and axially ligated OH on the tin ion as revealed by X-ray diffraction analysis. An unexpected dimeric structure was also observed during an attempt to grow crystals of 2Sn. These characteristic behaviors indicate that the ring-fixation aptitude of octaphyrin is quite sensitive to the nature of metal ions even for the same group 14 elements.

Propriedades volumétricas, viscosimétricas, acústicas e espectroscópicas de soluções líquidas binárias contendo gama-valerolactona (GVL) e álcoois

Substances derived from biomass have called attention, once these compounds belong to the group of renewable solvents, whose physicochemical properties present great potential for applications in several areas of science and industry, namely in biorefineries. Therefore, thermodynamic properties of systems containing such liquids is of practical interest, because experimental data can be used in modeling in order to improve processes or yet to develop and verify new models and solution theories, which have shown their complexity. The present project aims at studying excess thermodynamic properties, that quantify the real solution deviation in comparison to the ideal one, and spectroscopic analyses of binary liquid systems constituted of gamma-valerolactone (GVL) + alcohols (ethanol, 1-propanol, 1-butanol or 1- pentanol). For this purpose, original values of density, speed of sound and dynamic viscosity were determined for these solutions in the whole composition range and in temperatures T = (293.15 – 313.15) K under ambient pressure (92.3 kPa). From these experimental results, it was possible to calculate volumetric properties such as excess molar volume (Vm E ), acoustic property as deviation in isentropic compressibility (??S), viscometric as deviation in viscosity (??) and excess Gibbs energy of activation of viscous flow (?G *E). These properties resulted in negative values at all conditions, except for Vm E , which was totally negative only in ethanol-GVL system. To complete the thermodynamic discussion, both nuclear magnetic resonance (1H-NMR and 13C-NMR) and infrared (ATR-FTIR) spectroscopies have been performed, whose spectra proved the existence of weak hydrogen bondings between GVLalcohol

Investigation of the Thermo-Mechanical Properties of Blend Films Based on Hemicelluloses and Cellulose

This study presents an effective and convenient approach to prepare blend films with enhanced mechanical and thermodynamic properties by incorporation of carboxymethyl cellulose (CMC) into quaternized hemicelluloses (QH). The structures and properties of films were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and tensile testing, respectively. From the SEM pictures, tight, homogeneous, and smooth surfaces of films were obtained. In addition, the transparencies of the blend films were increased with the increasing of CMC content. The results of mechanical properties indicated that the blend film prepared from QH and CMC (1 : 2 m/m) had a tensile strength of 65.2 MPa. It suggested that the addition of CMC was contributed to mechanical properties by strong electrostatic interactions and the enhanced hydrogen bondings with QH. These results provide insights into the understanding of the structural relationships of bioblend films in coating and packaging application.

Spectroscopic study on the molecular polar arrangement and anchoring mechanism in crystalline DR1 films deposited on ITO by electric field assisted PVD process

We report the results of a systematic study for the elucidation of detailed molecular arrangements in Disperse Red 1(DR1) films prepared by electric field assisted physical vapor deposition (EFA-PVD) method on ITO substrate with varied field strength. Aside from confirming the periodic molecular chain structure reported previously, the electric field induced increase of crystallinity is corroborated by the enhanced crystalline appearance in the SEM images of the films deposited with increased applied field up to a certain limit. The optical spectroscopic measurements in both the transmission and reflection modes clearly show that instead of the anti-parallel polar arrangement found previously in films deposited without the applied electric field, it is the parallel arrangements of molecular aggregates that are found in the currently produced films which offer its potential application for the generation of second harmonic (SH) light. A detailed analysis of the additional FTIR-RAS data further reveals the formation of hydrogen bondings in the head-to-tail stacking along the molecular chain responsible for its periodic structure, as well as those between the DR1 hydroxyl end groups and the oxide components in the ITO substrate which provides the molecular immobilizing or anchoring mechanism for the deposited films. This explains in turn, the improved film stability and the formation of the highly desirable parallel polar arrangement of the DR1 molecules in the deposited films, promising for SHG and other related nonlinear optical (NLO) applications.

Anion influences on reactivity and NMR spectroscopic features of NHC precursors

The influences of 16 different counteranions on hydrogen-bondings, C–H acidities and 1JC2–H coupling constants of azolium salts have been studied.